The patch titled
Subject: lib/zlib: DFLTCC deflate does not write all available bits for Z_NO_FLUSH
has been added to the -mm mm-nonmm-unstable branch. Its filename is
lib-zlib-dfltcc-deflate-does-not-write-all-available-bits-for-z_no_flush.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-zlib-dfltcc-deflate-does-not-write-all-available-bits-for-z_no_flush.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx>
Subject: lib/zlib: DFLTCC deflate does not write all available bits for Z_NO_FLUSH
Date: Tue, 21 Feb 2023 14:16:17 +0100
DFLTCC deflate with Z_NO_FLUSH might generate a corrupted stream when the
output buffer is not large enough to fit all the deflate output at once.
The problem takes place on closing the deflate block since flush_pending()
might leave some output bits not written. Similar problem for software
deflate with Z_BLOCK flush option (not supported by kernel zlib deflate)
has been fixed a while ago in userspace zlib but the fix never got to the
kernel.
Now flush_pending() flushes the bit buffer before copying out the byte
buffer, in order to really flush as much as possible.
Currently there are no users of DFLTCC deflate with Z_NO_FLUSH option in
the kernel so the problem remained hidden for a while.
This commit is based on the old zlib commit:
https://github.com/madler/zlib/commit/0b828b4
Link: https://lkml.kernel.org/r/20230221131617.3369978-2-zaslonko@xxxxxxxxxxxxx
Signed-off-by: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx>
Acked-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/zlib_deflate/defutil.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/lib/zlib_deflate/defutil.h~lib-zlib-dfltcc-deflate-does-not-write-all-available-bits-for-z_no_flush
+++ a/lib/zlib_deflate/defutil.h
@@ -420,9 +420,11 @@ static inline void flush_pending(
z_streamp strm
)
{
+ unsigned len;
deflate_state *s = (deflate_state *) strm->state;
- unsigned len = s->pending;
+ bi_flush(s);
+ len = s->pending;
if (len > strm->avail_out) len = strm->avail_out;
if (len == 0) return;
_
Patches currently in -mm which might be from zaslonko@xxxxxxxxxxxxx are
lib-zlib-dfltcc-deflate-does-not-write-all-available-bits-for-z_no_flush.patch
