* Kees Cook <keescook@xxxxxxxxxxxx> [230929 13:19]:
> From: Sebastian Ott <sebott@xxxxxxxxxx>
>
> 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.
>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Fixes: 2e7ce7d354f2 ("mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()")
> Signed-off-by: Sebastian Ott <sebott@xxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> mm/mmap.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 34d2337ace59..c8996fe847c9 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -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;
> --
> 2.34.1
>
