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609 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Aleksa Sarai
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1bc82070fa |
namei: allow nd_jump_link() to produce errors
In preparation for LOOKUP_NO_MAGICLINKS, it's necessary to add the ability for nd_jump_link() to return an error which the corresponding get_link() caller must propogate back up to the VFS. Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
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Linus Torvalds
|
2954152298 |
Merge branch 'proc-cmdline' (/proc/<pid>/cmdline fixes)
This fixes two problems reported with the cmdline simplification and
cleanup last year:
- the setproctitle() special cases didn't quite match the original
semantics, and it can be noticeable:
https://lore.kernel.org/lkml/alpine.LNX.2.21.1904052326230.3249@kich.toxcorp.com/
- it could leak an uninitialized byte from the temporary buffer under
the right (wrong) circustances:
https://lore.kernel.org/lkml/20190712160913.17727-1-izbyshev@ispras.ru/
It rewrites the logic entirely, splitting it into two separate commits
(and two separate functions) for the two different cases ("unedited
cmdline" vs "setproctitle() has been used to change the command line").
* proc-cmdline:
/proc/<pid>/cmdline: add back the setproctitle() special case
/proc/<pid>/cmdline: remove all the special cases
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Linus Torvalds
|
d26d0cd97c |
/proc/<pid>/cmdline: add back the setproctitle() special case
This makes the setproctitle() special case very explicit indeed, and
handles it with a separate helper function entirely. In the process, it
re-instates the original semantics of simply stopping at the first NUL
character when the original last NUL character is no longer there.
[ The original semantics can still be seen in mm/util.c: get_cmdline()
that is limited to a fixed-size buffer ]
This makes the logic about when we use the string lengths etc much more
obvious, and makes it easier to see what we do and what the two very
different cases are.
Note that even when we allow walking past the end of the argument array
(because the setproctitle() might have overwritten and overflowed the
original argv[] strings), we only allow it when it overflows into the
environment region if it is immediately adjacent.
[ Fixed for missing 'count' checks noted by Alexey Izbyshev ]
Link: https://lore.kernel.org/lkml/alpine.LNX.2.21.1904052326230.3249@kich.toxcorp.com/
Fixes:
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Linus Torvalds
|
3d712546d8 |
/proc/<pid>/cmdline: remove all the special cases
Start off with a clean slate that only reads exactly from arg_start to
arg_end, without any oddities. This simplifies the code and in the
process removes the case that caused us to potentially leak an
uninitialized byte from the temporary kernel buffer.
Note that in order to start from scratch with an understandable base,
this simplifies things _too_ much, and removes all the legacy logic to
handle setproctitle() having changed the argument strings.
We'll add back those special cases very differently in the next commit.
Link: https://lore.kernel.org/lkml/20190712160913.17727-1-izbyshev@ispras.ru/
Fixes:
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Shakeel Butt
|
ac311a14c6 |
oom: decouple mems_allowed from oom_unkillable_task
Commit |
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Shakeel Butt
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6ba749ee78 |
mm, oom: remove redundant task_in_mem_cgroup() check
oom_unkillable_task() can be called from three different contexts i.e. global OOM, memcg OOM and oom_score procfs interface. At the moment oom_unkillable_task() does a task_in_mem_cgroup() check on the given process. Since there is no reason to perform task_in_mem_cgroup() check for global OOM and oom_score procfs interface, those contexts provide NULL memcg and skips the task_in_mem_cgroup() check. However for memcg OOM context, the oom_unkillable_task() is always called from mem_cgroup_scan_tasks() and thus task_in_mem_cgroup() check becomes redundant and effectively dead code. So, just remove the task_in_mem_cgroup() check altogether. Link: http://lkml.kernel.org/r/20190624212631.87212-2-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Paul Jackson <pj@sgi.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Konstantin Khlebnikov
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cd9e2bb827 |
proc: use down_read_killable mmap_sem for /proc/pid/map_files
Do not remain stuck forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation. It seems ->d_revalidate() could return any error (except ECHILD) to abort validation and pass error as result of lookup sequence. [akpm@linux-foundation.org: fix proc_map_files_lookup() return value, per Andrei] Link: http://lkml.kernel.org/r/156007493995.3335.9595044802115356911.stgit@buzz Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reviewed-by: Roman Gushchin <guro@fb.com> Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com> Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Koutný <mkoutny@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Linus Torvalds
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3431a940bb |
Merge branch 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 AVX512 status update from Ingo Molnar: "This adds a new ABI that the main scheduler probably doesn't want to deal with but HPC job schedulers might want to use: the AVX512_elapsed_ms field in the new /proc/<pid>/arch_status task status file, which allows the user-space job scheduler to cluster such tasks, to avoid turbo frequency drops" * 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: Documentation/filesystems/proc.txt: Add arch_status file x86/process: Add AVX-512 usage elapsed time to /proc/pid/arch_status proc: Add /proc/<pid>/arch_status |
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Christian Brauner
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30d158b143 |
proc: remove useless d_is_dir() check
Remove the d_is_dir() check from tgid_pidfd_to_pid(). It is pointless since you should never get &proc_tgid_base_operations for f_op on a non-directory. Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Christian Brauner <christian@brauner.io> |
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Aubrey Li
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68bc30bb9f |
proc: Add /proc/<pid>/arch_status
Exposing architecture specific per process information is useful for various reasons. An example is the AVX512 usage on x86 which is important for task placement for power/performance optimizations. Adding this information to the existing /prcc/pid/status file would be the obvious choise, but it has been agreed on that a explicit arch_status file is better in separating the generic and architecture specific information. [ tglx: Massage changelog ] Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andrew Morton <akpm@linux-foundation.org> Cc: peterz@infradead.org Cc: hpa@zytor.com Cc: ak@linux.intel.com Cc: tim.c.chen@linux.intel.com Cc: dave.hansen@intel.com Cc: arjan@linux.intel.com Cc: adobriyan@gmail.com Cc: aubrey.li@intel.com Cc: linux-api@vger.kernel.org Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andi Kleen <ak@linux.intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Linux API <linux-api@vger.kernel.org> Link: https://lkml.kernel.org/r/20190606012236.9391-1-aubrey.li@linux.intel.com |
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Lin Feng
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e02c9b0d65 |
kernel/latencytop.c: rename clear_all_latency_tracing to clear_tsk_latency_tracing
The name clear_all_latency_tracing is misleading, in fact which only clear per task's latency_record[], and we do have another function named clear_global_latency_tracing which clear the global latency_record[] buffer. Link: http://lkml.kernel.org/r/20190226114602.16902-1-linf@wangsu.com Signed-off-by: Lin Feng <linf@wangsu.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Fabian Frederick <fabf@skynet.be> Cc: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Linus Torvalds
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f72dae2089 |
Merge tag 'selinux-pr-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull selinux updates from Paul Moore:
"We've got a few SELinux patches for the v5.2 merge window, the
highlights are below:
- Add LSM hooks, and the SELinux implementation, for proper labeling
of kernfs. While we are only including the SELinux implementation
here, the rest of the LSM folks have given the hooks a thumbs-up.
- Update the SELinux mdp (Make Dummy Policy) script to actually work
on a modern system.
- Disallow userspace to change the LSM credentials via
/proc/self/attr when the task's credentials are already overridden.
The change was made in procfs because all the LSM folks agreed this
was the Right Thing To Do and duplicating it across each LSM was
going to be annoying"
* tag 'selinux-pr-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
proc: prevent changes to overridden credentials
selinux: Check address length before reading address family
kernfs: fix xattr name handling in LSM helpers
MAINTAINERS: update SELinux file patterns
selinux: avoid uninitialized variable warning
selinux: remove useless assignments
LSM: lsm_hooks.h - fix missing colon in docstring
selinux: Make selinux_kernfs_init_security static
kernfs: initialize security of newly created nodes
selinux: implement the kernfs_init_security hook
LSM: add new hook for kernfs node initialization
kernfs: use simple_xattrs for security attributes
selinux: try security xattr after genfs for kernfs filesystems
kernfs: do not alloc iattrs in kernfs_xattr_get
kernfs: clean up struct kernfs_iattrs
scripts/selinux: fix build
selinux: use kernel linux/socket.h for genheaders and mdp
scripts/selinux: modernize mdp
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Paul Moore
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35a196bef4 |
proc: prevent changes to overridden credentials
Prevent userspace from changing the the /proc/PID/attr values if the task's credentials are currently overriden. This not only makes sense conceptually, it also prevents some really bizarre error cases caused when trying to commit credentials to a task with overridden credentials. Cc: <stable@vger.kernel.org> Reported-by: "chengjian (D)" <cj.chengjian@huawei.com> Signed-off-by: Paul Moore <paul@paul-moore.com> Acked-by: John Johansen <john.johansen@canonical.com> Acked-by: James Morris <james.morris@microsoft.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> |
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Thomas Gleixner
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e988e5ec18 |
proc: Simplify task stack retrieval
Replace the indirection through struct stack_trace with an invocation of the storage array based interface. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexey Dobriyan <adobriyan@gmail.com> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Alexander Potapenko <glider@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: linux-mm@kvack.org Cc: David Rientjes <rientjes@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: kasan-dev@googlegroups.com Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Akinobu Mita <akinobu.mita@gmail.com> Cc: Christoph Hellwig <hch@lst.de> Cc: iommu@lists.linux-foundation.org Cc: Robin Murphy <robin.murphy@arm.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Cc: David Sterba <dsterba@suse.com> Cc: Chris Mason <clm@fb.com> Cc: Josef Bacik <josef@toxicpanda.com> Cc: linux-btrfs@vger.kernel.org Cc: dm-devel@redhat.com Cc: Mike Snitzer <snitzer@redhat.com> Cc: Alasdair Kergon <agk@redhat.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: intel-gfx@lists.freedesktop.org Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: dri-devel@lists.freedesktop.org Cc: David Airlie <airlied@linux.ie> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Tom Zanussi <tom.zanussi@linux.intel.com> Cc: Miroslav Benes <mbenes@suse.cz> Cc: linux-arch@vger.kernel.org Link: https://lkml.kernel.org/r/20190425094801.589304463@linutronix.de |
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Thomas Gleixner
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accddc41b9 |
latency_top: Remove the ULONG_MAX stack trace hackery
No architecture terminates the stack trace with ULONG_MAX anymore. The consumer terminates on the first zero entry or at the number of entries, so no functional change. Remove the cruft. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Alexander Potapenko <glider@google.com> Link: https://lkml.kernel.org/r/20190410103644.853527514@linutronix.de |
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Steven Rostedt (Red Hat)
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631b7abacd |
ptrace: Remove maxargs from task_current_syscall()
task_current_syscall() has a single user that passes in 6 for maxargs, which is the maximum arguments that can be used to get system calls from syscall_get_arguments(). Instead of passing in a number of arguments to grab, just get 6 arguments. The args argument even specifies that it's an array of 6 items. This will also allow changing syscall_get_arguments() to not get a variable number of arguments, but always grab 6. Linus also suggested not passing in a bunch of arguments to task_current_syscall() but to instead pass in a pointer to a structure, and just fill the structure. struct seccomp_data has almost all the parameters that is needed except for the stack pointer (sp). As seccomp_data is part of uapi, and I'm afraid to change it, a new structure was created "syscall_info", which includes seccomp_data and adds the "sp" field. Link: http://lkml.kernel.org/r/20161107213233.466776454@goodmis.org Cc: Andy Lutomirski <luto@kernel.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
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Linus Torvalds
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a9dce6679d |
Merge tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull pidfd system call from Christian Brauner:
"This introduces the ability to use file descriptors from /proc/<pid>/
as stable handles on struct pid. Even if a pid is recycled the handle
will not change. For a start these fds can be used to send signals to
the processes they refer to.
With the ability to use /proc/<pid> fds as stable handles on struct
pid we can fix a long-standing issue where after a process has exited
its pid can be reused by another process. If a caller sends a signal
to a reused pid it will end up signaling the wrong process.
With this patchset we enable a variety of use cases. One obvious
example is that we can now safely delegate an important part of
process management - sending signals - to processes other than the
parent of a given process by sending file descriptors around via scm
rights and not fearing that the given process will have been recycled
in the meantime. It also allows for easy testing whether a given
process is still alive or not by sending signal 0 to a pidfd which is
quite handy.
There has been some interest in this feature e.g. from systems
management (systemd, glibc) and container managers. I have requested
and gotten comments from glibc to make sure that this syscall is
suitable for their needs as well. In the future I expect it to take on
most other pid-based signal syscalls. But such features are left for
the future once they are needed.
This has been sitting in linux-next for quite a while and has not
caused any issues. It comes with selftests which verify basic
functionality and also test that a recycled pid cannot be signaled via
a pidfd.
Jon has written about a prior version of this patchset. It should
cover the basic functionality since not a lot has changed since then:
https://lwn.net/Articles/773459/
The commit message for the syscall itself is extensively documenting
the syscall, including it's functionality and extensibility"
* tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
selftests: add tests for pidfd_send_signal()
signal: add pidfd_send_signal() syscall
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Kent Overstreet
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94f8f3b02e |
proc: commit to genradix
The new generic radix trees have a simpler API and implementation, and no limitations on number of elements, so all flex_array users are being converted Link: http://lkml.kernel.org/r/20181217131929.11727-6-kent.overstreet@gmail.com Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com> Reviewed-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Eric Paris <eparis@parisplace.org> Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Paul Moore <paul@paul-moore.com> Cc: Pravin B Shelar <pshelar@ovn.org> Cc: Shaohua Li <shli@kernel.org> Cc: Stephen Smalley <sds@tycho.nsa.gov> Cc: Vlad Yasevich <vyasevich@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Alexey Dobriyan
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d5a572a4cb |
proc: calculate end pointer for /proc/*/* lookup at compile time
Compilers like to transform loops like
for (i = 0; i < n; i++) {
[use p[i]]
}
into
for (p = p0; p < end; p++) {
...
}
Do it by hand, so that it results in overall simpler loop
and smaller code.
Space savings:
$ ./scripts/bloat-o-meter ../vmlinux-001 ../obj/vmlinux
add/remove: 0/0 grow/shrink: 2/1 up/down: 4/-9 (-5)
Function old new delta
proc_tid_base_lookup 17 19 +2
proc_tgid_base_lookup 17 19 +2
proc_pident_lookup 179 170 -9
The same could be done to proc_pident_readdir(), but the code becomes
bigger for some reason.
[sfr@canb.auug.org.au: merge fix for proc_pident_lookup() API change]
Link: http://lkml.kernel.org/r/20190131160135.4a8ae70b@canb.auug.org.au
Link: http://lkml.kernel.org/r/20190114200422.GB9680@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: James Morris <jmorris@namei.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds
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be37f21a08 |
Merge tag 'audit-pr-20190305' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit
Pull audit updates from Paul Moore: "A lucky 13 audit patches for v5.1. Despite the rather large diffstat, most of the changes are from two bug fix patches that move code from one Kconfig option to another. Beyond that bit of churn, the remaining changes are largely cleanups and bug-fixes as we slowly march towards container auditing. It isn't all boring though, we do have a couple of new things: file capabilities v3 support, and expanded support for filtering on filesystems to solve problems with remote filesystems. All changes pass the audit-testsuite. Please merge for v5.1" * tag 'audit-pr-20190305' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit: audit: mark expected switch fall-through audit: hide auditsc_get_stamp and audit_serial prototypes audit: join tty records to their syscall audit: remove audit_context when CONFIG_ AUDIT and not AUDITSYSCALL audit: remove unused actx param from audit_rule_match audit: ignore fcaps on umount audit: clean up AUDITSYSCALL prototypes and stubs audit: more filter PATH records keyed on filesystem magic audit: add support for fcaps v3 audit: move loginuid and sessionid from CONFIG_AUDITSYSCALL to CONFIG_AUDIT audit: add syscall information to CONFIG_CHANGE records audit: hand taken context to audit_kill_trees for syscall logging audit: give a clue what CONFIG_CHANGE op was involved |
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Linus Torvalds
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ae5906ceee |
Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull security subsystem updates from James Morris: - Extend LSM stacking to allow sharing of cred, file, ipc, inode, and task blobs. This paves the way for more full-featured LSMs to be merged, and is specifically aimed at LandLock and SARA LSMs. This work is from Casey and Kees. - There's a new LSM from Micah Morton: "SafeSetID gates the setid family of syscalls to restrict UID/GID transitions from a given UID/GID to only those approved by a system-wide whitelist." This feature is currently shipping in ChromeOS. * 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (62 commits) keys: fix missing __user in KEYCTL_PKEY_QUERY LSM: Update list of SECURITYFS users in Kconfig LSM: Ignore "security=" when "lsm=" is specified LSM: Update function documentation for cap_capable security: mark expected switch fall-throughs and add a missing break tomoyo: Bump version. LSM: fix return value check in safesetid_init_securityfs() LSM: SafeSetID: add selftest LSM: SafeSetID: remove unused include LSM: SafeSetID: 'depend' on CONFIG_SECURITY LSM: Add 'name' field for SafeSetID in DEFINE_LSM LSM: add SafeSetID module that gates setid calls LSM: add SafeSetID module that gates setid calls tomoyo: Allow multiple use_group lines. tomoyo: Coding style fix. tomoyo: Swicth from cred->security to task_struct->security. security: keys: annotate implicit fall throughs security: keys: annotate implicit fall throughs security: keys: annotate implicit fall through capabilities:: annotate implicit fall through ... |
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Alexey Dobriyan
|
08b5577513 |
proc: use seq_puts() everywhere
seq_printf() without format specifiers == faster seq_puts() Link: http://lkml.kernel.org/r/20190114200545.GC9680@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Zhikang Zhang
|
867aaccf1f |
proc: remove unused argument in proc_pid_lookup()
[adobriyan@gmail.com: delete "extern" from prototype] Link: http://lkml.kernel.org/r/20190114195635.GA9372@avx2 Signed-off-by: Zhikang Zhang <zhangzhikang1@huawei.com> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Christian Brauner
|
3eb39f4793 |
signal: add pidfd_send_signal() syscall
The kill() syscall operates on process identifiers (pid). After a process
has exited its pid can be reused by another process. If a caller sends a
signal to a reused pid it will end up signaling the wrong process. This
issue has often surfaced and there has been a push to address this problem [1].
This patch uses file descriptors (fd) from proc/<pid> as stable handles on
struct pid. Even if a pid is recycled the handle will not change. The fd
can be used to send signals to the process it refers to.
Thus, the new syscall pidfd_send_signal() is introduced to solve this
problem. Instead of pids it operates on process fds (pidfd).
/* prototype and argument /*
long pidfd_send_signal(int pidfd, int sig, siginfo_t *info, unsigned int flags);
/* syscall number 424 */
The syscall number was chosen to be 424 to align with Arnd's rework in his
y2038 to minimize merge conflicts (cf. [25]).
In addition to the pidfd and signal argument it takes an additional
siginfo_t and flags argument. If the siginfo_t argument is NULL then
pidfd_send_signal() is equivalent to kill(<positive-pid>, <signal>). If it
is not NULL pidfd_send_signal() is equivalent to rt_sigqueueinfo().
The flags argument is added to allow for future extensions of this syscall.
It currently needs to be passed as 0. Failing to do so will cause EINVAL.
/* pidfd_send_signal() replaces multiple pid-based syscalls */
The pidfd_send_signal() syscall currently takes on the job of
rt_sigqueueinfo(2) and parts of the functionality of kill(2), Namely, when a
positive pid is passed to kill(2). It will however be possible to also
replace tgkill(2) and rt_tgsigqueueinfo(2) if this syscall is extended.
/* sending signals to threads (tid) and process groups (pgid) */
Specifically, the pidfd_send_signal() syscall does currently not operate on
process groups or threads. This is left for future extensions.
In order to extend the syscall to allow sending signal to threads and
process groups appropriately named flags (e.g. PIDFD_TYPE_PGID, and
PIDFD_TYPE_TID) should be added. This implies that the flags argument will
determine what is signaled and not the file descriptor itself. Put in other
words, grouping in this api is a property of the flags argument not a
property of the file descriptor (cf. [13]). Clarification for this has been
requested by Eric (cf. [19]).
When appropriate extensions through the flags argument are added then
pidfd_send_signal() can additionally replace the part of kill(2) which
operates on process groups as well as the tgkill(2) and
rt_tgsigqueueinfo(2) syscalls.
How such an extension could be implemented has been very roughly sketched
in [14], [15], and [16]. However, this should not be taken as a commitment
to a particular implementation. There might be better ways to do it.
Right now this is intentionally left out to keep this patchset as simple as
possible (cf. [4]).
/* naming */
The syscall had various names throughout iterations of this patchset:
- procfd_signal()
- procfd_send_signal()
- taskfd_send_signal()
In the last round of reviews it was pointed out that given that if the
flags argument decides the scope of the signal instead of different types
of fds it might make sense to either settle for "procfd_" or "pidfd_" as
prefix. The community was willing to accept either (cf. [17] and [18]).
Given that one developer expressed strong preference for the "pidfd_"
prefix (cf. [13]) and with other developers less opinionated about the name
we should settle for "pidfd_" to avoid further bikeshedding.
The "_send_signal" suffix was chosen to reflect the fact that the syscall
takes on the job of multiple syscalls. It is therefore intentional that the
name is not reminiscent of neither kill(2) nor rt_sigqueueinfo(2). Not the
fomer because it might imply that pidfd_send_signal() is a replacement for
kill(2), and not the latter because it is a hassle to remember the correct
spelling - especially for non-native speakers - and because it is not
descriptive enough of what the syscall actually does. The name
"pidfd_send_signal" makes it very clear that its job is to send signals.
/* zombies */
Zombies can be signaled just as any other process. No special error will be
reported since a zombie state is an unreliable state (cf. [3]). However,
this can be added as an extension through the @flags argument if the need
ever arises.
/* cross-namespace signals */
The patch currently enforces that the signaler and signalee either are in
the same pid namespace or that the signaler's pid namespace is an ancestor
of the signalee's pid namespace. This is done for the sake of simplicity
and because it is unclear to what values certain members of struct
siginfo_t would need to be set to (cf. [5], [6]).
/* compat syscalls */
It became clear that we would like to avoid adding compat syscalls
(cf. [7]). The compat syscall handling is now done in kernel/signal.c
itself by adding __copy_siginfo_from_user_generic() which lets us avoid
compat syscalls (cf. [8]). It should be noted that the addition of
__copy_siginfo_from_user_any() is caused by a bug in the original
implementation of rt_sigqueueinfo(2) (cf. 12).
With upcoming rework for syscall handling things might improve
significantly (cf. [11]) and __copy_siginfo_from_user_any() will not gain
any additional callers.
/* testing */
This patch was tested on x64 and x86.
/* userspace usage */
An asciinema recording for the basic functionality can be found under [9].
With this patch a process can be killed via:
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
static inline int do_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
unsigned int flags)
{
#ifdef __NR_pidfd_send_signal
return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
#else
return -ENOSYS;
#endif
}
int main(int argc, char *argv[])
{
int fd, ret, saved_errno, sig;
if (argc < 3)
exit(EXIT_FAILURE);
fd = open(argv[1], O_DIRECTORY | O_CLOEXEC);
if (fd < 0) {
printf("%s - Failed to open \"%s\"\n", strerror(errno), argv[1]);
exit(EXIT_FAILURE);
}
sig = atoi(argv[2]);
printf("Sending signal %d to process %s\n", sig, argv[1]);
ret = do_pidfd_send_signal(fd, sig, NULL, 0);
saved_errno = errno;
close(fd);
errno = saved_errno;
if (ret < 0) {
printf("%s - Failed to send signal %d to process %s\n",
strerror(errno), sig, argv[1]);
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
/* Q&A
* Given that it seems the same questions get asked again by people who are
* late to the party it makes sense to add a Q&A section to the commit
* message so it's hopefully easier to avoid duplicate threads.
*
* For the sake of progress please consider these arguments settled unless
* there is a new point that desperately needs to be addressed. Please make
* sure to check the links to the threads in this commit message whether
* this has not already been covered.
*/
Q-01: (Florian Weimer [20], Andrew Morton [21])
What happens when the target process has exited?
A-01: Sending the signal will fail with ESRCH (cf. [22]).
Q-02: (Andrew Morton [21])
Is the task_struct pinned by the fd?
A-02: No. A reference to struct pid is kept. struct pid - as far as I
understand - was created exactly for the reason to not require to
pin struct task_struct (cf. [22]).
Q-03: (Andrew Morton [21])
Does the entire procfs directory remain visible? Just one entry
within it?
A-03: The same thing that happens right now when you hold a file descriptor
to /proc/<pid> open (cf. [22]).
Q-04: (Andrew Morton [21])
Does the pid remain reserved?
A-04: No. This patchset guarantees a stable handle not that pids are not
recycled (cf. [22]).
Q-05: (Andrew Morton [21])
Do attempts to signal that fd return errors?
A-05: See {Q,A}-01.
Q-06: (Andrew Morton [22])
Is there a cleaner way of obtaining the fd? Another syscall perhaps.
A-06: Userspace can already trivially retrieve file descriptors from procfs
so this is something that we will need to support anyway. Hence,
there's no immediate need to add another syscalls just to make
pidfd_send_signal() not dependent on the presence of procfs. However,
adding a syscalls to get such file descriptors is planned for a
future patchset (cf. [22]).
Q-07: (Andrew Morton [21] and others)
This fd-for-a-process sounds like a handy thing and people may well
think up other uses for it in the future, probably unrelated to
signals. Are the code and the interface designed to permit such
future applications?
A-07: Yes (cf. [22]).
Q-08: (Andrew Morton [21] and others)
Now I think about it, why a new syscall? This thing is looking
rather like an ioctl?
A-08: This has been extensively discussed. It was agreed that a syscall is
preferred for a variety or reasons. Here are just a few taken from
prior threads. Syscalls are safer than ioctl()s especially when
signaling to fds. Processes are a core kernel concept so a syscall
seems more appropriate. The layout of the syscall with its four
arguments would require the addition of a custom struct for the
ioctl() thereby causing at least the same amount or even more
complexity for userspace than a simple syscall. The new syscall will
replace multiple other pid-based syscalls (see description above).
The file-descriptors-for-processes concept introduced with this
syscall will be extended with other syscalls in the future. See also
[22], [23] and various other threads already linked in here.
Q-09: (Florian Weimer [24])
What happens if you use the new interface with an O_PATH descriptor?
A-09:
pidfds opened as O_PATH fds cannot be used to send signals to a
process (cf. [2]). Signaling processes through pidfds is the
equivalent of writing to a file. Thus, this is not an operation that
operates "purely at the file descriptor level" as required by the
open(2) manpage. See also [4].
/* References */
[1]: https://lore.kernel.org/lkml/20181029221037.87724-1-dancol@google.com/
[2]: https://lore.kernel.org/lkml/874lbtjvtd.fsf@oldenburg2.str.redhat.com/
[3]: https://lore.kernel.org/lkml/20181204132604.aspfupwjgjx6fhva@brauner.io/
[4]: https://lore.kernel.org/lkml/20181203180224.fkvw4kajtbvru2ku@brauner.io/
[5]: https://lore.kernel.org/lkml/20181121213946.GA10795@mail.hallyn.com/
[6]: https://lore.kernel.org/lkml/20181120103111.etlqp7zop34v6nv4@brauner.io/
[7]: https://lore.kernel.org/lkml/36323361-90BD-41AF-AB5B-EE0D7BA02C21@amacapital.net/
[8]: https://lore.kernel.org/lkml/87tvjxp8pc.fsf@xmission.com/
[9]: https://asciinema.org/a/IQjuCHew6bnq1cr78yuMv16cy
[11]: https://lore.kernel.org/lkml/F53D6D38-3521-4C20-9034-5AF447DF62FF@amacapital.net/
[12]: https://lore.kernel.org/lkml/87zhtjn8ck.fsf@xmission.com/
[13]: https://lore.kernel.org/lkml/871s6u9z6u.fsf@xmission.com/
[14]: https://lore.kernel.org/lkml/20181206231742.xxi4ghn24z4h2qki@brauner.io/
[15]: https://lore.kernel.org/lkml/20181207003124.GA11160@mail.hallyn.com/
[16]: https://lore.kernel.org/lkml/20181207015423.4miorx43l3qhppfz@brauner.io/
[17]: https://lore.kernel.org/lkml/CAGXu5jL8PciZAXvOvCeCU3wKUEB_dU-O3q0tDw4uB_ojMvDEew@mail.gmail.com/
[18]: https://lore.kernel.org/lkml/20181206222746.GB9224@mail.hallyn.com/
[19]: https://lore.kernel.org/lkml/20181208054059.19813-1-christian@brauner.io/
[20]: https://lore.kernel.org/lkml/8736rebl9s.fsf@oldenburg.str.redhat.com/
[21]: https://lore.kernel.org/lkml/20181228152012.dbf0508c2508138efc5f2bbe@linux-foundation.org/
[22]: https://lore.kernel.org/lkml/20181228233725.722tdfgijxcssg76@brauner.io/
[23]: https://lwn.net/Articles/773459/
[24]: https://lore.kernel.org/lkml/8736rebl9s.fsf@oldenburg.str.redhat.com/
[25]: https://lore.kernel.org/lkml/CAK8P3a0ej9NcJM8wXNPbcGUyOUZYX+VLoDFdbenW3s3114oQZw@mail.gmail.com/
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jann Horn <jannh@google.com>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Tycho Andersen <tycho@tycho.ws>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Serge Hallyn <serge@hallyn.com>
Acked-by: Aleksa Sarai <cyphar@cyphar.com>
|
||
Michal Hocko
|
b2b469939e |
proc, oom: do not report alien mms when setting oom_score_adj
Tetsuo has reported that creating a thousands of processes sharing MM
without SIGHAND (aka alien threads) and setting
/proc/<pid>/oom_score_adj will swamp the kernel log and takes ages [1]
to finish. This is especially worrisome that all that printing is done
under RCU lock and this can potentially trigger RCU stall or softlockup
detector.
The primary reason for the printk was to catch potential users who might
depend on the behavior prior to
|