The patch titled
Subject: mm: fix vm_brk_flags() to not bail out while holding lock
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-fix-vm_brk_flags-to-not-bail-out-while-holding-lock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-vm_brk_flags-to-not-bail-out-while-holding-lock.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sebastian Ott <sebott@xxxxxxxxxx>
Subject: mm: fix vm_brk_flags() to not bail out while holding lock
Date: Fri, 29 Sep 2023 10:19:41 -0700
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@xxxxxxxxxx
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>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/mmap.c~mm-fix-vm_brk_flags-to-not-bail-out-while-holding-lock
+++ a/mm/mmap.c
@@ -3157,13 +3157,13 @@ int vm_brk_flags(unsigned long addr, uns
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;
_
Patches currently in -mm which might be from sebott@xxxxxxxxxx are
mm-fix-vm_brk_flags-to-not-bail-out-while-holding-lock.patch
