linux.git/kernel/sys.c, branch v5.10.195

kernel/sys.c: fix and improve control flow in __sys_setres[ug]id()

2023-04-26T09:27:38+00:00

commit 659c0ce1cb9efc7f58d380ca4bb2a51ae9e30553 upstream.

Linux Security Modules (LSMs) that implement the "capable" hook will
usually emit an access denial message to the audit log whenever they
"block" the current task from using the given capability based on their
security policy.

The occurrence of a denial is used as an indication that the given task
has attempted an operation that requires the given access permission, so
the callers of functions that perform LSM permission checks must take care
to avoid calling them too early (before it is decided if the permission is
actually needed to perform the requested operation).

The __sys_setres[ug]id() functions violate this convention by first
calling ns_capable_setid() and only then checking if the operation
requires the capability or not.  It means that any caller that has the
capability granted by DAC (task's capability set) but not by MAC (LSMs)
will generate a "denied" audit record, even if is doing an operation for
which the capability is not required.

Fix this by reordering the checks such that ns_capable_setid() is checked
last and -EPERM is returned immediately if it returns false.

While there, also do two small optimizations:
* move the capability check before prepare_creds() and
* bail out early in case of a no-op.

Link: https://lkml.kernel.org/r/20230217162154.837549-1-omosnace@redhat.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Ondrej Mosnacek 
Cc: Eric W. Biederman 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

prlimit: do_prlimit needs to have a speculation check

2023-01-24T06:19:58+00:00

commit 739790605705ddcf18f21782b9c99ad7d53a8c11 upstream.

do_prlimit() adds the user-controlled resource value to a pointer that
will subsequently be dereferenced.  In order to help prevent this
codepath from being used as a spectre "gadget" a barrier needs to be
added after checking the range.

Reported-by: Jordy Zomer 
Tested-by: Jordy Zomer 
Suggested-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

prctl: allow to setup brk for et_dyn executables

2021-09-26T12:08:57+00:00

commit e1fbbd073137a9d63279f6bf363151a938347640 upstream.

Keno Fischer reported that when a binray loaded via ld-linux-x the
prctl(PR_SET_MM_MAP) doesn't allow to setup brk value because it lays
before mm:end_data.

For example a test program shows

 | # ~/t
 |
 | start_code      401000
 | end_code        401a15
 | start_stack     7ffce4577dd0
 | start_data	   403e10
 | end_data        40408c
 | start_brk	   b5b000
 | sbrk(0)         b5b000

and when executed via ld-linux

 | # /lib64/ld-linux-x86-64.so.2 ~/t
 |
 | start_code      7fc25b0a4000
 | end_code        7fc25b0c4524
 | start_stack     7fffcc6b2400
 | start_data	   7fc25b0ce4c0
 | end_data        7fc25b0cff98
 | start_brk	   55555710c000
 | sbrk(0)         55555710c000

This of course prevent criu from restoring such programs.  Looking into
how kernel operates with brk/start_brk inside brk() syscall I don't see
any problem if we allow to setup brk/start_brk without checking for
end_data.  Even if someone pass some weird address here on a purpose then
the worst possible result will be an unexpected unmapping of existing vma
(own vma, since prctl works with the callers memory) but test for
RLIMIT_DATA is still valid and a user won't be able to gain more memory in
case of expanding VMAs via new values shipped with prctl call.

Link: https://lkml.kernel.org/r/20210121221207.GB2174@grain
Fixes: bbdc6076d2e5 ("binfmt_elf: move brk out of mmap when doing direct loader exec")
Signed-off-by: Cyrill Gorcunov 
Reported-by: Keno Fischer 
Acked-by: Andrey Vagin 
Tested-by: Andrey Vagin 
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Kirill Tkhai 
Cc: Eric W. Biederman 
Cc: Pavel Tikhomirov 
Cc: Alexander Mikhalitsyn 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

Revert "Add a reference to ucounts for each cred"

2021-09-08T06:49:00+00:00

This reverts commit b2c4d9a33cc2dec7466f97eba2c4dd571ad798a5 which is
commit 905ae01c4ae2ae3df05bb141801b1db4b7d83c61 upstream.

This commit should not have been applied to the 5.10.y stable tree, so
revert it.

Reported-by: "Eric W. Biederman" 
Link: https://lore.kernel.org/r/87v93k4bl6.fsf@disp2133
Cc: Alexey Gladkov 
Cc: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

Add a reference to ucounts for each cred

2021-07-14T14:55:48+00:00

[ Upstream commit 905ae01c4ae2ae3df05bb141801b1db4b7d83c61 ]

For RLIMIT_NPROC and some other rlimits the user_struct that holds the
global limit is kept alive for the lifetime of a process by keeping it
in struct cred. Adding a pointer to ucounts in the struct cred will
allow to track RLIMIT_NPROC not only for user in the system, but for
user in the user_namespace.

Updating ucounts may require memory allocation which may fail. So, we
cannot change cred.ucounts in the commit_creds() because this function
cannot fail and it should always return 0. For this reason, we modify
cred.ucounts before calling the commit_creds().

Changelog

v6:
* Fix null-ptr-deref in is_ucounts_overlimit() detected by trinity. This
  error was caused by the fact that cred_alloc_blank() left the ucounts
  pointer empty.

Reported-by: kernel test robot 
Signed-off-by: Alexey Gladkov 
Link: https://lkml.kernel.org/r/b37aaef28d8b9b0d757e07ba6dd27281bbe39259.1619094428.git.legion@kernel.org
Signed-off-by: Eric W. Biederman 
Signed-off-by: Sasha Levin

kernel/sys.c: fix prototype of prctl_get_tid_address()

2020-10-25T18:44:16+00:00

tid_addr is not a "pointer to (pointer to int in userspace)"; it is in
fact a "pointer to (pointer to int in userspace) in userspace".  So
sparse rightfully complains about passing a kernel pointer to
put_user().

Reported-by: kernel test robot 
Signed-off-by: Rasmus Villemoes 
Signed-off-by: Linus Torvalds

Merge tag 'safesetid-5.10' of git://github.com/micah-morton/linux

2020-10-25T17:45:26+00:00

Pull SafeSetID updates from Micah Morton:
 "The changes are mostly contained to within the SafeSetID LSM, with the
  exception of a few 1-line changes to change some ns_capable() calls to
  ns_capable_setid() -- causing a flag (CAP_OPT_INSETID) to be set that
  is examined by SafeSetID code and nothing else in the kernel.

  The changes to SafeSetID internally allow for setting up GID
  transition security policies, as already existed for UIDs"

* tag 'safesetid-5.10' of git://github.com/micah-morton/linux:
  LSM: SafeSetID: Fix warnings reported by test bot
  LSM: SafeSetID: Add GID security policy handling
  LSM: Signal to SafeSetID when setting group IDs

kernel/sys.c: replace do_brk with do_brk_flags in comment of prctl_set_mm_map()

2020-10-16T18:11:19+00:00

Replace do_brk with do_brk_flags in comment of prctl_set_mm_map(), since
do_brk was removed in following commit.

Fixes: bb177a732c4369 ("mm: do not bug_on on incorrect length in __mm_populate()")
Signed-off-by: Liao Pingfang 
Signed-off-by: Yi Wang 
Signed-off-by: Andrew Morton 
Link: https://lkml.kernel.org/r/1600650751-43127-1-git-send-email-wang.yi59@zte.com.cn
Signed-off-by: Linus Torvalds

LSM: Signal to SafeSetID when setting group IDs

2020-10-13T16:17:34+00:00

For SafeSetID to properly gate set*gid() calls, it needs to know whether
ns_capable() is being called from within a sys_set*gid() function or is
being called from elsewhere in the kernel. This allows SafeSetID to deny
CAP_SETGID to restricted groups when they are attempting to use the
capability for code paths other than updating GIDs (e.g. setting up
userns GID mappings). This is the identical approach to what is
currently done for CAP_SETUID.

NOTE: We also add signaling to SafeSetID from the setgroups() syscall,
as we have future plans to restrict a process' ability to set
supplementary groups in addition to what is added in this series for
restricting setting of the primary group.

Signed-off-by: Thomas Cedeno 
Signed-off-by: Micah Morton

treewide: Use fallthrough pseudo-keyword

2020-08-23T22:36:59+00:00

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva