Messages in this thread Patch in this message | | | From | Kees Cook <> | Subject | [PATCH] mm: Fix vm_brk_flags() to not bail out while holding lock | Date | Fri, 29 Sep 2023 10:19:41 -0700 |
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From: Sebastian Ott <sebott@redhat.com>
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@linux-foundation.org> Cc: Liam R. Howlett <Liam.Howlett@Oracle.com> Cc: Yu Zhao <yuzhao@google.com> Cc: linux-mm@kvack.org Fixes: 2e7ce7d354f2 ("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> --- 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
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