Merge yet more updates from Andrew Morton:
- More MM work. 100ish more to go. Mike Rapoport's "mm: remove
__ARCH_HAS_5LEVEL_HACK" series should fix the current ppc issue
- Various other little subsystems
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (127 commits)
lib/ubsan.c: fix gcc-10 warnings
tools/testing/selftests/vm: remove duplicate headers
selftests: vm: pkeys: fix multilib builds for x86
selftests: vm: pkeys: use the correct page size on powerpc
selftests/vm/pkeys: override access right definitions on powerpc
selftests/vm/pkeys: test correct behaviour of pkey-0
selftests/vm/pkeys: introduce a sub-page allocator
selftests/vm/pkeys: detect write violation on a mapped access-denied-key page
selftests/vm/pkeys: associate key on a mapped page and detect write violation
selftests/vm/pkeys: associate key on a mapped page and detect access violation
selftests/vm/pkeys: improve checks to determine pkey support
selftests/vm/pkeys: fix assertion in test_pkey_alloc_exhaust()
selftests/vm/pkeys: fix number of reserved powerpc pkeys
selftests/vm/pkeys: introduce powerpc support
selftests/vm/pkeys: introduce generic pkey abstractions
selftests: vm: pkeys: use the correct huge page size
selftests/vm/pkeys: fix alloc_random_pkey() to make it really random
selftests/vm/pkeys: fix assertion in pkey_disable_set/clear()
selftests/vm/pkeys: fix pkey_disable_clear()
selftests: vm: pkeys: add helpers for pkey bits
...
Currently copy_string_kernel is just a wrapper around copy_strings that
simplifies the calling conventions and uses set_fs to allow passing a
kernel pointer. But due to the fact the we only need to handle a single
kernel argument pointer, the logic can be sigificantly simplified while
getting rid of the set_fs.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Link: http://lkml.kernel.org/r/20200501104105.2621149-3-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull execve updates from Eric Biederman:
"Last cycle for the Nth time I ran into bugs and quality of
implementation issues related to exec that could not be easily be
fixed because of the way exec is implemented. So I have been digging
into exec and cleanup up what I can.
I don't think I have exec sorted out enough to fix the issues I
started with but I have made some headway this cycle with 4 sets of
changes.
- promised cleanups after introducing exec_update_mutex
- trivial cleanups for exec
- control flow simplifications
- remove the recomputation of bprm->cred
The net result is code that is a bit easier to understand and work
with and a decrease in the number of lines of code (if you don't count
the added tests)"
* 'exec-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (24 commits)
exec: Compute file based creds only once
exec: Add a per bprm->file version of per_clear
binfmt_elf_fdpic: fix execfd build regression
selftests/exec: Add binfmt_script regression test
exec: Remove recursion from search_binary_handler
exec: Generic execfd support
exec/binfmt_script: Don't modify bprm->buf and then return -ENOEXEC
exec: Move the call of prepare_binprm into search_binary_handler
exec: Allow load_misc_binary to call prepare_binprm unconditionally
exec: Convert security_bprm_set_creds into security_bprm_repopulate_creds
exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds
exec: Teach prepare_exec_creds how exec treats uids & gids
exec: Set the point of no return sooner
exec: Move handling of the point of no return to the top level
exec: Run sync_mm_rss before taking exec_update_mutex
exec: Fix spelling of search_binary_handler in a comment
exec: Move the comment from above de_thread to above unshare_sighand
exec: Rename flush_old_exec begin_new_exec
exec: Move most of setup_new_exec into flush_old_exec
exec: In setup_new_exec cache current in the local variable me
...
Pull proc updates from Eric Biederman:
"This has four sets of changes:
- modernize proc to support multiple private instances
- ensure we see the exit of each process tid exactly
- remove has_group_leader_pid
- use pids not tasks in posix-cpu-timers lookup
Alexey updated proc so each mount of proc uses a new superblock. This
allows people to actually use mount options with proc with no fear of
messing up another mount of proc. Given the kernel's internal mounts
of proc for things like uml this was a real problem, and resulted in
Android's hidepid mount options being ignored and introducing security
issues.
The rest of the changes are small cleanups and fixes that came out of
my work to allow this change to proc. In essence it is swapping the
pids in de_thread during exec which removes a special case the code
had to handle. Then updating the code to stop handling that special
case"
* 'proc-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
proc: proc_pid_ns takes super_block as an argument
remove the no longer needed pid_alive() check in __task_pid_nr_ns()
posix-cpu-timers: Replace __get_task_for_clock with pid_for_clock
posix-cpu-timers: Replace cpu_timer_pid_type with clock_pid_type
posix-cpu-timers: Extend rcu_read_lock removing task_struct references
signal: Remove has_group_leader_pid
exec: Remove BUG_ON(has_group_leader_pid)
posix-cpu-timer: Unify the now redundant code in lookup_task
posix-cpu-timer: Tidy up group_leader logic in lookup_task
proc: Ensure we see the exit of each process tid exactly once
rculist: Add hlists_swap_heads_rcu
proc: Use PIDTYPE_TGID in next_tgid
Use proc_pid_ns() to get pid_namespace from the proc superblock
proc: use named enums for better readability
proc: use human-readable values for hidepid
docs: proc: add documentation for "hidepid=4" and "subset=pid" options and new mount behavior
proc: add option to mount only a pids subset
proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option
proc: allow to mount many instances of proc in one pid namespace
proc: rename struct proc_fs_info to proc_fs_opts
Move the computation of creds from prepare_binfmt into begin_new_exec
so that the creds need only be computed once. This is just code
reorganization no semantic changes of any kind are made.
Moving the computation is safe. I have looked through the kernel and
verified none of the binfmts look at bprm->cred directly, and that
there are no helpers that look at bprm->cred indirectly. Which means
that it is not a problem to compute the bprm->cred later in the
execution flow as it is not used until it becomes current->cred.
A new function bprm_creds_from_file is added to contain the work that
needs to be done. bprm_creds_from_file first computes which file
bprm->executable or most likely bprm->file that the bprm->creds
will be computed from.
The funciton bprm_fill_uid is updated to receive the file instead of
accessing bprm->file. The now unnecessary work needed to reset the
bprm->cred->euid, and bprm->cred->egid is removed from brpm_fill_uid.
A small comment to document that bprm_fill_uid now only deals with the
work to handle suid and sgid files. The default case is already
heandled by prepare_exec_creds.
The function security_bprm_repopulate_creds is renamed
security_bprm_creds_from_file and now is explicitly passed the file
from which to compute the creds. The documentation of the
bprm_creds_from_file security hook is updated to explain when the hook
is called and what it needs to do. The file is passed from
cap_bprm_creds_from_file into get_file_caps so that the caps are
computed for the appropriate file. The now unnecessary work in
cap_bprm_creds_from_file to reset the ambient capabilites has been
removed. A small comment to document that the work of
cap_bprm_creds_from_file is to read capabilities from the files
secureity attribute and derive capabilities from the fact the
user had uid 0 has been added.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
There is a small bug in the code that recomputes parts of bprm->cred
for every bprm->file. The code never recomputes the part of
clear_dangerous_personality_flags it is responsible for.
Which means that in practice if someone creates a sgid script
the interpreter will not be able to use any of:
READ_IMPLIES_EXEC
ADDR_NO_RANDOMIZE
ADDR_COMPAT_LAYOUT
MMAP_PAGE_ZERO.
This accentially clearing of personality flags probably does
not matter in practice because no one has complained
but it does make the code more difficult to understand.
Further remaining bug compatible prevents the recomputation from being
removed and replaced by simply computing bprm->cred once from the
final bprm->file.
Making this change removes the last behavior difference between
computing bprm->creds from the final file and recomputing
bprm->cred several times. Which allows this behavior change
to be justified for it's own reasons, and for any but hunts
looking into why the behavior changed to wind up here instead
of in the code that will follow that computes bprm->cred
from the final bprm->file.
This small logic bug appears to have existed since the code
started clearing dangerous personality bits.
History Tree: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Fixes: 1bb0fa189c6a ("[PATCH] NX: clean up legacy binary support")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Recursion in kernel code is generally a bad idea as it can overflow
the kernel stack. Recursion in exec also hides that the code is
looping and that the loop changes bprm->file.
Instead of recursing in search_binary_handler have the methods that
would recurse set bprm->interpreter and return 0. Modify exec_binprm
to loop when bprm->interpreter is set. Consolidate all of the
reassignments of bprm->file in that loop to make it clear what is
going on.
The structure of the new loop in exec_binprm is that all errors return
immediately, while successful completion (ret == 0 &&
!bprm->interpreter) just breaks out of the loop and runs what
exec_bprm has always run upon successful completion.
Fail if the an interpreter is being call after execfd has been set.
The code has never properly handled an interpreter being called with
execfd being set and with reassignments of bprm->file and the
assignment of bprm->executable in generic code it has finally become
possible to test and fail when if this problematic condition happens.
With the reassignments of bprm->file and the assignment of
bprm->executable moved into the generic code add a test to see if
bprm->executable is being reassigned.
In search_binary_handler remove the test for !bprm->file. With all
reassignments of bprm->file moved to exec_binprm bprm->file can never
be NULL in search_binary_handler.
Link: https://lkml.kernel.org/r/87sgfwyd84.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Most of the support for passing the file descriptor of an executable
to an interpreter already lives in the generic code and in binfmt_elf.
Rework the fields in binfmt_elf that deal with executable file
descriptor passing to make executable file descriptor passing a first
class concept.
Move the fd_install from binfmt_misc into begin_new_exec after the new
creds have been installed. This means that accessing the file through
/proc/<pid>/fd/N is able to see the creds for the new executable
before allowing access to the new executables files.
Performing the install of the executables file descriptor after
the point of no return also means that nothing special needs to
be done on error. The exiting of the process will close all
of it's open files.
Move the would_dump from binfmt_misc into begin_new_exec right
after would_dump is called on the bprm->file. This makes it
obvious this case exists and that no nesting of bprm->file is
currently supported.
In binfmt_misc the movement of fd_install into generic code means
that it's special error exit path is no longer needed.
Link: https://lkml.kernel.org/r/87y2poyd91.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Add a flag preserve_creds that binfmt_misc can set to prevent
credentials from being updated. This allows binfmt_misc to always
call prepare_binprm. Allowing the credential computation logic to be
consolidated.
Not replacing the credentials with the interpreters credentials is
safe because because an open file descriptor to the executable is
passed to the interpreter. As the interpreter does not need to
reopen the executable it is guaranteed to see the same file that
exec sees.
Ref: c407c033de84 ("[PATCH] binfmt_misc: improve calculation of interpreter's credentials")
Link: https://lkml.kernel.org/r/87imgszrwo.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Rename bprm->cap_elevated to bprm->active_secureexec and initialize it
in prepare_binprm instead of in cap_bprm_set_creds. Initializing
bprm->active_secureexec in prepare_binprm allows multiple
implementations of security_bprm_repopulate_creds to play nicely with
each other.
Rename security_bprm_set_creds to security_bprm_reopulate_creds to
emphasize that this path recomputes part of bprm->cred. This
recomputation avoids the time of check vs time of use problems that
are inherent in unix #! interpreters.
In short two renames and a move in the location of initializing
bprm->active_secureexec.
Link: https://lkml.kernel.org/r/87o8qkzrxp.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Today security_bprm_set_creds has several implementations:
apparmor_bprm_set_creds, cap_bprm_set_creds, selinux_bprm_set_creds,
smack_bprm_set_creds, and tomoyo_bprm_set_creds.
Except for cap_bprm_set_creds they all test bprm->called_set_creds and
return immediately if it is true. The function cap_bprm_set_creds
ignores bprm->calld_sed_creds entirely.
Create a new LSM hook security_bprm_creds_for_exec that is called just
before prepare_binprm in __do_execve_file, resulting in a LSM hook
that is called exactly once for the entire of exec. Modify the bits
of security_bprm_set_creds that only want to be called once per exec
into security_bprm_creds_for_exec, leaving only cap_bprm_set_creds
behind.
Remove bprm->called_set_creds all of it's former users have been moved
to security_bprm_creds_for_exec.
Add or upate comments a appropriate to bring them up to date and
to reflect this change.
Link: https://lkml.kernel.org/r/87v9kszrzh.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com> # For the LSM and Smack bits
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
The change to exec is relevant to the cleanup work I have been doing.
Merge it here so that I can build on top of it, and so hopefully
that other merge logic can pick up on this and see how to deal
with the conflict between that change and my exec cleanup work.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
I goofed when I added mm->user_ns support to would_dump. I missed the
fact that in the case of binfmt_loader, binfmt_em86, binfmt_misc, and
binfmt_script bprm->file is reassigned. Which made the move of
would_dump from setup_new_exec to __do_execve_file before exec_binprm
incorrect as it can result in would_dump running on the script instead
of the interpreter of the script.
The net result is that the code stopped making unreadable interpreters
undumpable. Which allows them to be ptraced and written to disk
without special permissions. Oops.
The move was necessary because the call in set_new_exec was after
bprm->mm was no longer valid.
To correct this mistake move the misplaced would_dump from
__do_execve_file into flos_old_exec, before exec_mmap is called.
I tested and confirmed that without this fix I can attach with gdb to
a script with an unreadable interpreter, and with this fix I can not.
Cc: stable@vger.kernel.org
Fixes: f84df2a6f2 ("exec: Ensure mm->user_ns contains the execed files")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Make the code more robust by marking the point of no return sooner.
This ensures that future code changes don't need to worry about how
they return errors if they are past this point.
This results in no actual change in behavior as __do_execve_file does
not force SIGSEGV when there is a pending fatal signal pending past
the point of no return. Further the only error returns from de_thread
and exec_mmap that can occur result in fatal signals being pending.
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87sgga5klu.fsf_-_@x220.int.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Move the handing of the point of no return from search_binary_handler
into __do_execve_file so that it is easier to find, and to keep
things robust in the face of change.
Make it clear that an existing fatal signal will take precedence over
a forced SIGSEGV by not forcing SIGSEGV if a fatal signal is already
pending. This does not change the behavior but it saves a reader
of the code the tedium of reading and understanding force_sig
and the signal delivery code.
Update the comment in begin_new_exec about where SIGSEGV is forced.
Keep point_of_no_return from being a mystery by documenting
what the code is doing where it forces SIGSEGV if the
code is past the point of no return.
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87y2q25knl.fsf_-_@x220.int.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
There is and has been for a very long time been a lot more going on in
flush_old_exec than just flushing the old state. After the movement
of code from setup_new_exec there is a whole lot more going on than
just flushing the old executables state.
Rename flush_old_exec to begin_new_exec to more accurately reflect
what this function does.
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Greg Ungerer <gerg@linux-m68k.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Michel Lespinasse
Christoph Hellwig
Linus Torvalds
Eric W. Biederman