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mm: fix vm_brk_flags() to not bail out while holding lock

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Calling vm_brk_flags() with flags set other than VM_EXEC will exit the
function without releasing the mmap_write_lock.

Just do the sanity check before the lock is acquired.  This doesn't fix an
actual issue since no caller sets a flag other than VM_EXEC.

Link: https://lkml.kernel.org/r/20230929171937.work.697-kees@kernel.org
Fixes: 2e7ce7d354 ("mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()")
Signed-off-by: Sebastian Ott <sebott@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sebastian Ott 2023-09-29 10:19:41 -07:00 • committed by Andrew Morton
parent 51f6253775
commit e0f81ab1e4
1 changed files with 3 additions and 3 deletions
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6
mm/mmap.c
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@ -3143,13 +3143,13 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
if (!len)
return 0;
if (mmap_write_lock_killable(mm))
return -EINTR;
/* Until we need other flags, refuse anything except VM_EXEC. */
if ((flags & (~VM_EXEC)) != 0)
return -EINVAL;
if (mmap_write_lock_killable(mm))
return -EINTR;
ret = check_brk_limits(addr, len);
if (ret)
goto limits_failed;