Cyrill Gorcunov reports that I broke the fdinfo files with commit
30a08bf2d3 ("proc: move fd symlink i_mode calculations into
tid_fd_revalidate()"), and he's quite right.
The tid_fd_revalidate() function is not just used for the <tid>/fd
symlinks, it's also used for the <tid>/fdinfo/<fd> files, and the
permission model for those are different.
So do the dynamic symlink permission handling just for symlinks, making
the fdinfo files once more appear as the proper regular files they are.
Of course, Al Viro argued (probably correctly) that we shouldn't do the
symlink permission games at all, and make the symlinks always just be
the normal 'lrwxrwxrwx'. That would have avoided this issue too, but
since somebody noticed that the permissions had changed (which was the
reason for that original commit 30a08bf2d3 in the first place), people
do apparently use this feature.
[ Basically, you can use the symlink permission data as a cheap "fdinfo"
replacement, since you see whether the file is open for reading and/or
writing by just looking at st_mode of the symlink. So the feature
does make sense, even if the pain it has caused means we probably
shouldn't have done it to begin with. ]
Reported-and-tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When we do checkpoint of a task we need to know the list of children the
task, has but there is no easy and fast way to generate reverse
parent->children chain from arbitrary <pid> (while a parent pid is
provided in "PPid" field of /proc/<pid>/status).
So instead of walking over all pids in the system (creating one big
process tree in memory, just to figure out which children a task has) --
we add explicit /proc/<pid>/task/<tid>/children entry, because the kernel
already has this kind of information but it is not yet exported.
This is a first level children, not the whole process tree.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
rcu_read_lock()/rcu_read_unlock() is nop for TINY_RCU, but is not a nop
for, say, PREEMPT_RCU.
proc_fill_cache() is called without RCU lock, there is no need to
lock/unlock on error path, simply jump out of the loop.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Similar to e268337dfe ("proc: clean up and fix /proc/<pid>/mem
handling"), move the check of permission to open(), this will simplify
read() code.
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The oom_score_adj scale ranges from -1000 to 1000 and represents the
proportion of memory available to the process at allocation time. This
means an oom_score_adj value of 300, for example, will bias a process as
though it was using an extra 30.0% of available memory and a value of
-350 will discount 35.0% of available memory from its usage.
The oom killer badness heuristic also uses this scale to report the oom
score for each eligible process in determining the "best" process to
kill. Thus, it can only differentiate each process's memory usage by
0.1% of system RAM.
On large systems, this can end up being a large amount of memory: 256MB
on 256GB systems, for example.
This can be fixed by having the badness heuristic to use the actual
memory usage in scoring threads and then normalizing it to the
oom_score_adj scale for userspace. This results in better comparison
between eligible threads for kill and no change from the userspace
perspective.
Suggested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Tested-by: Dave Jones <davej@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull user namespace enhancements from Eric Biederman:
"This is a course correction for the user namespace, so that we can
reach an inexpensive, maintainable, and reasonably complete
implementation.
Highlights:
- Config guards make it impossible to enable the user namespace and
code that has not been converted to be user namespace safe.
- Use of the new kuid_t type ensures the if you somehow get past the
config guards the kernel will encounter type errors if you enable
user namespaces and attempt to compile in code whose permission
checks have not been updated to be user namespace safe.
- All uids from child user namespaces are mapped into the initial
user namespace before they are processed. Removing the need to add
an additional check to see if the user namespace of the compared
uids remains the same.
- With the user namespaces compiled out the performance is as good or
better than it is today.
- For most operations absolutely nothing changes performance or
operationally with the user namespace enabled.
- The worst case performance I could come up with was timing 1
billion cache cold stat operations with the user namespace code
enabled. This went from 156s to 164s on my laptop (or 156ns to
164ns per stat operation).
- (uid_t)-1 and (gid_t)-1 are reserved as an internal error value.
Most uid/gid setting system calls treat these value specially
anyway so attempting to use -1 as a uid would likely cause
entertaining failures in userspace.
- If setuid is called with a uid that can not be mapped setuid fails.
I have looked at sendmail, login, ssh and every other program I
could think of that would call setuid and they all check for and
handle the case where setuid fails.
- If stat or a similar system call is called from a context in which
we can not map a uid we lie and return overflowuid. The LFS
experience suggests not lying and returning an error code might be
better, but the historical precedent with uids is different and I
can not think of anything that would break by lying about a uid we
can't map.
- Capabilities are localized to the current user namespace making it
safe to give the initial user in a user namespace all capabilities.
My git tree covers all of the modifications needed to convert the core
kernel and enough changes to make a system bootable to runlevel 1."
Fix up trivial conflicts due to nearby independent changes in fs/stat.c
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (46 commits)
userns: Silence silly gcc warning.
cred: use correct cred accessor with regards to rcu read lock
userns: Convert the move_pages, and migrate_pages permission checks to use uid_eq
userns: Convert cgroup permission checks to use uid_eq
userns: Convert tmpfs to use kuid and kgid where appropriate
userns: Convert sysfs to use kgid/kuid where appropriate
userns: Convert sysctl permission checks to use kuid and kgids.
userns: Convert proc to use kuid/kgid where appropriate
userns: Convert ext4 to user kuid/kgid where appropriate
userns: Convert ext3 to use kuid/kgid where appropriate
userns: Convert ext2 to use kuid/kgid where appropriate.
userns: Convert devpts to use kuid/kgid where appropriate
userns: Convert binary formats to use kuid/kgid where appropriate
userns: Add negative depends on entries to avoid building code that is userns unsafe
userns: signal remove unnecessary map_cred_ns
userns: Teach inode_capable to understand inodes whose uids map to other namespaces.
userns: Fail exec for suid and sgid binaries with ids outside our user namespace.
userns: Convert stat to return values mapped from kuids and kgids
userns: Convert user specfied uids and gids in chown into kuids and kgid
userns: Use uid_eq gid_eq helpers when comparing kuids and kgids in the vfs
...
Merge misc fixes from Andrew Morton.
* emailed from Andrew Morton <akpm@linux-foundation.org>: (4 patches)
frv: delete incorrect task prototypes causing compile fail
slub: missing test for partial pages flush work in flush_all()
fs, proc: fix ABBA deadlock in case of execution attempt of map_files/ entries
drivers/rtc/rtc-pl031.c: configure correct wday for 2000-01-01
Instead of doing the i_mode calculations at proc_fd_instantiate() time,
move them into tid_fd_revalidate(), which is where the other inode state
(notably uid/gid information) is updated too.
Otherwise we'll end up with stale i_mode information if an fd is re-used
while the dentry still hangs around. Not that anything really *cares*
(symlink permissions don't really matter), but Tetsuo Handa noticed that
the owner read/write bits don't always match the state of the
readability of the file descriptor, and we _used_ to get this right a
long time ago in a galaxy far, far away.
Besides, aside from fixing an ugly detail (that has apparently been this
way since commit 61a2878402: "proc: Remove the hard coded inode
numbers" in 2006), this removes more lines of code than it adds. And it
just makes sense to update i_mode in the same place we update i_uid/gid.
Al Viro correctly points out that we could just do the inode fill in the
inode iops ->getattr() function instead. However, that does require
somewhat slightly more invasive changes, and adds yet *another* lookup
of the file descriptor. We need to do the revalidate() for other
reasons anyway, and have the file descriptor handy, so we might as well
fill in the information at this point.
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
map_files/ entries are never supposed to be executed, still curious
minds might try to run them, which leads to the following deadlock
======================================================
[ INFO: possible circular locking dependency detected ]
3.4.0-rc4-24406-g841e6a6 #121 Not tainted
-------------------------------------------------------
bash/1556 is trying to acquire lock:
(&sb->s_type->i_mutex_key#8){+.+.+.}, at: do_lookup+0x267/0x2b1
but task is already holding lock:
(&sig->cred_guard_mutex){+.+.+.}, at: prepare_bprm_creds+0x2d/0x69
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&sig->cred_guard_mutex){+.+.+.}:
validate_chain+0x444/0x4f4
__lock_acquire+0x387/0x3f8
lock_acquire+0x12b/0x158
__mutex_lock_common+0x56/0x3a9
mutex_lock_killable_nested+0x40/0x45
lock_trace+0x24/0x59
proc_map_files_lookup+0x5a/0x165
__lookup_hash+0x52/0x73
do_lookup+0x276/0x2b1
walk_component+0x3d/0x114
do_last+0xfc/0x540
path_openat+0xd3/0x306
do_filp_open+0x3d/0x89
do_sys_open+0x74/0x106
sys_open+0x21/0x23
tracesys+0xdd/0xe2
-> #0 (&sb->s_type->i_mutex_key#8){+.+.+.}:
check_prev_add+0x6a/0x1ef
validate_chain+0x444/0x4f4
__lock_acquire+0x387/0x3f8
lock_acquire+0x12b/0x158
__mutex_lock_common+0x56/0x3a9
mutex_lock_nested+0x40/0x45
do_lookup+0x267/0x2b1
walk_component+0x3d/0x114
link_path_walk+0x1f9/0x48f
path_openat+0xb6/0x306
do_filp_open+0x3d/0x89
open_exec+0x25/0xa0
do_execve_common+0xea/0x2f9
do_execve+0x43/0x45
sys_execve+0x43/0x5a
stub_execve+0x6c/0xc0
This is because prepare_bprm_creds grabs task->signal->cred_guard_mutex
and when do_lookup happens we try to grab task->signal->cred_guard_mutex
again in lock_trace.
Fix it using plain ptrace_may_access() helper in proc_map_files_lookup()
and in proc_map_files_readdir() instead of lock_trace(), the caller must
be CAP_SYS_ADMIN granted anyway.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Vasiliy Kulikov <segoon@openwall.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>
- Convert the old uid mapping functions into compatibility wrappers
- Add a uid/gid mapping layer from user space uid and gids to kernel
internal uids and gids that is extent based for simplicty and speed.
* Working with number space after mapping uids/gids into their kernel
internal version adds only mapping complexity over what we have today,
leaving the kernel code easy to understand and test.
- Add proc files /proc/self/uid_map /proc/self/gid_map
These files display the mapping and allow a mapping to be added
if a mapping does not exist.
- Allow entering the user namespace without a uid or gid mapping.
Since we are starting with an existing user our uids and gids
still have global mappings so are still valid and useful they just don't
have local mappings. The requirement for things to work are global uid
and gid so it is odd but perfectly fine not to have a local uid
and gid mapping.
Not requiring global uid and gid mappings greatly simplifies
the logic of setting up the uid and gid mappings by allowing
the mappings to be set after the namespace is created which makes the
slight weirdness worth it.
- Make the mappings in the initial user namespace to the global
uid/gid space explicit. Today it is an identity mapping
but in the future we may want to twist this for debugging, similar
to what we do with jiffies.
- Document the memory ordering requirements of setting the uid and
gid mappings. We only allow the mappings to be set once
and there are no pointers involved so the requirments are
trivial but a little atypical.
Performance:
In this scheme for the permission checks the performance is expected to
stay the same as the actuall machine instructions should remain the same.
The worst case I could think of is ls -l on a large directory where
all of the stat results need to be translated with from kuids and
kgids to uids and gids. So I benchmarked that case on my laptop
with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache.
My benchmark consisted of going to single user mode where nothing else
was running. On an ext4 filesystem opening 1,000,000 files and looping
through all of the files 1000 times and calling fstat on the
individuals files. This was to ensure I was benchmarking stat times
where the inodes were in the kernels cache, but the inode values were
not in the processors cache. My results:
v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled)
v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled)
v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled)
All of the configurations ran in roughly 120ns when I performed tests
that ran in the cpu cache.
So in summary the performance impact is:
1ns improvement in the worst case with user namespace support compiled out.
8ns aka 5% slowdown in the worst case with user namespace support compiled in.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Pull x32 support for x86-64 from Ingo Molnar:
"This tree introduces the X32 binary format and execution mode for x86:
32-bit data space binaries using 64-bit instructions and 64-bit kernel
syscalls.
This allows applications whose working set fits into a 32 bits address
space to make use of 64-bit instructions while using a 32-bit address
space with shorter pointers, more compressed data structures, etc."
Fix up trivial context conflicts in arch/x86/{Kconfig,vdso/vma.c}
* 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (71 commits)
x32: Fix alignment fail in struct compat_siginfo
x32: Fix stupid ia32/x32 inversion in the siginfo format
x32: Add ptrace for x32
x32: Switch to a 64-bit clock_t
x32: Provide separate is_ia32_task() and is_x32_task() predicates
x86, mtrr: Use explicit sizing and padding for the 64-bit ioctls
x86/x32: Fix the binutils auto-detect
x32: Warn and disable rather than error if binutils too old
x32: Only clear TIF_X32 flag once
x32: Make sure TS_COMPAT is cleared for x32 tasks
fs: Remove missed ->fds_bits from cessation use of fd_set structs internally
fs: Fix close_on_exec pointer in alloc_fdtable
x32: Drop non-__vdso weak symbols from the x32 VDSO
x32: Fix coding style violations in the x32 VDSO code
x32: Add x32 VDSO support
x32: Allow x32 to be configured
x32: If configured, add x32 system calls to system call tables
x32: Handle process creation
x32: Signal-related system calls
x86: Add #ifdef CONFIG_COMPAT to <asm/sys_ia32.h>
...
Wrap accesses to the fd_sets in struct fdtable (for recording open files and
close-on-exec flags) so that we can move away from using fd_sets since we
abuse the fd_set structs by not allocating the full-sized structure under
normal circumstances and by non-core code looking at the internals of the
fd_sets.
The first abuse means that use of FD_ZERO() on these fd_sets is not permitted,
since that cannot be told about their abnormal lengths.
This introduces six wrapper functions for setting, clearing and testing
close-on-exec flags and fd-is-open flags:
void __set_close_on_exec(int fd, struct fdtable *fdt);
void __clear_close_on_exec(int fd, struct fdtable *fdt);
bool close_on_exec(int fd, const struct fdtable *fdt);
void __set_open_fd(int fd, struct fdtable *fdt);
void __clear_open_fd(int fd, struct fdtable *fdt);
bool fd_is_open(int fd, const struct fdtable *fdt);
Note that I've prepended '__' to the names of the set/clear functions because
they require the caller to hold a lock to use them.
Note also that I haven't added wrappers for looking behind the scenes at the
the array. Possibly that should exist too.
Signed-off-by: David Howells <dhowells@redhat.com>
Link: http://lkml.kernel.org/r/20120216174942.23314.1364.stgit@warthog.procyon.org.uk
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
This fixes the race in process_vm_core found by Oleg (see
http://article.gmane.org/gmane.linux.kernel/1235667/
for details).
This has been updated since I last sent it as the creation of the new
mm_access() function did almost exactly the same thing as parts of the
previous version of this patch did.
In order to use mm_access() even when /proc isn't enabled, we move it to
kernel/fork.c where other related process mm access functions already
are.
Signed-off-by: Chris Yeoh <yeohc@au1.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Once /proc/pid/mem is opened, the memory can't be released until
mem_release() even if its owner exits.
Change mem_open() to do atomic_inc(mm_count) + mmput(), this only
pins mm_struct. Change mem_rw() to do atomic_inc_not_zero(mm_count)
before access_remote_vm(), this verifies that this mm is still alive.
I am not sure what should mem_rw() return if atomic_inc_not_zero()
fails. With this patch it returns zero to match the "mm == NULL" case,
may be it should return -EINVAL like it did before e268337d.
Perhaps it makes sense to add the additional fatal_signal_pending()
check into the main loop, to ensure we do not hold this memory if
the target task was oom-killed.
Cc: stable@kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
No functional changes, cleanup and preparation.
mem_read() and mem_write() are very similar. Move this code into the
new common helper, mem_rw(), which takes the additional "int write"
argument.
Cc: stable@kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit: (29 commits)
audit: no leading space in audit_log_d_path prefix
audit: treat s_id as an untrusted string
audit: fix signedness bug in audit_log_execve_info()
audit: comparison on interprocess fields
audit: implement all object interfield comparisons
audit: allow interfield comparison between gid and ogid
audit: complex interfield comparison helper
audit: allow interfield comparison in audit rules
Kernel: Audit Support For The ARM Platform
audit: do not call audit_getname on error
audit: only allow tasks to set their loginuid if it is -1
audit: remove task argument to audit_set_loginuid
audit: allow audit matching on inode gid
audit: allow matching on obj_uid
audit: remove audit_finish_fork as it can't be called
audit: reject entry,always rules
audit: inline audit_free to simplify the look of generic code
audit: drop audit_set_macxattr as it doesn't do anything
audit: inline checks for not needing to collect aux records
audit: drop some potentially inadvisable likely notations
...
Use evil merge to fix up grammar mistakes in Kconfig file.
Bad speling and horrible grammar (and copious swearing) is to be
expected, but let's keep it to commit messages and comments, rather than
expose it to users in config help texts or printouts.
Jüri Aedla reported that the /proc/<pid>/mem handling really isn't very
robust, and it also doesn't match the permission checking of any of the
other related files.
This changes it to do the permission checks at open time, and instead of
tracking the process, it tracks the VM at the time of the open. That
simplifies the code a lot, but does mean that if you hold the file
descriptor open over an execve(), you'll continue to read from the _old_
VM.
That is different from our previous behavior, but much simpler. If
somebody actually finds a load where this matters, we'll need to revert
this commit.
I suspect that nobody will ever notice - because the process mapping
addresses will also have changed as part of the execve. So you cannot
actually usefully access the fd across a VM change simply because all
the offsets for IO would have changed too.
Reported-by: Jüri Aedla <asd@ut.ee>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
At the moment we allow tasks to set their loginuid if they have
CAP_AUDIT_CONTROL. In reality we want tasks to set the loginuid when they
log in and it be impossible to ever reset. We had to make it mutable even
after it was once set (with the CAP) because on update and admin might have
to restart sshd. Now sshd would get his loginuid and the next user which
logged in using ssh would not be able to set his loginuid.
Systemd has changed how userspace works and allowed us to make the kernel
work the way it should. With systemd users (even admins) are not supposed
to restart services directly. The system will restart the service for
them. Thus since systemd is going to loginuid==-1, sshd would get -1, and
sshd would be allowed to set a new loginuid without special permissions.
If an admin in this system were to manually start an sshd he is inserting
himself into the system chain of trust and thus, logically, it's his
loginuid that should be used! Since we have old systems I make this a
Kconfig option.
Signed-off-by: Eric Paris <eparis@redhat.com>
