+ lib-ucs2_stringc-fix-out-of-bounds-read-in-ucs2_strnlen.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: lib/ucs2_string.c: fix out-of-bounds read in ucs2_strnlen()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     lib-ucs2_stringc-fix-out-of-bounds-read-in-ucs2_strnlen.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-ucs2_stringc-fix-out-of-bounds-read-in-ucs2_strnlen.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Vincent Mailhol <mailhol@kernel.org>
Subject: lib/ucs2_string.c: fix out-of-bounds read in ucs2_strnlen()
Date: Thu, 23 Jul 2026 21:40:31 +0200

Patch series "lib/ucs2_string.c: fix out-of-bounds read in
ucs2_strnlen()", v2.

This series fixes an off-by-one out-of-bounds read in ucs2_strnlen().

The first patch is the real fix, the second patch comes as a bonus and
fixes the code indentation.


This patch (of 2):

ucs2_strnlen() checks the current character before checking whether the
caller-provided maximum length has been reached.  If the input is not
NUL-terminated within that bound, the loop can read one ucs2_char_t past
the limit.

Test the length before dereferencing to prevent an off-by-one
out-of-bounds read.

Link: https://lore.kernel.org/20260723-fix-ucs2_strnlen-v2-0-9ea94e32a358@kernel.org
Link: https://lore.kernel.org/20260723-fix-ucs2_strnlen-v2-1-9ea94e32a358@kernel.org
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/ucs2_string.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/ucs2_string.c~lib-ucs2_stringc-fix-out-of-bounds-read-in-ucs2_strnlen
+++ a/lib/ucs2_string.c
@@ -8,7 +8,7 @@ ucs2_strnlen(const ucs2_char_t *s, size_
 {
         unsigned long length = 0;
 
-        while (*s++ != 0 && length < maxlength)
+	while (length < maxlength && *s++ != 0)
                 length++;
         return length;
 }
_

Patches currently in -mm which might be from mailhol@kernel.org are

lib-ucs2_stringc-fix-out-of-bounds-read-in-ucs2_strnlen.patch
lib-ucs2_stringc-fix-indentation.patch