This is a note to let you know that I've just added the patch titled
parisc: Fix ip_fast_csum
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
parisc-fix-ip_fast_csum.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 11907cfe3802582d4569c324a34575f21374c798
Author: Guenter Roeck <linux@xxxxxxxxxxxx>
Date: Sat Feb 10 09:55:26 2024 -0800
parisc: Fix ip_fast_csum
[ Upstream commit a2abae8f0b638c31bb9799d9dd847306e0d005bd ]
IP checksum unit tests report the following error when run on hppa/hppa64.
# test_ip_fast_csum: ASSERTION FAILED at lib/checksum_kunit.c:463
Expected ( u64)csum_result == ( u64)expected, but
( u64)csum_result == 33754 (0x83da)
( u64)expected == 10946 (0x2ac2)
not ok 4 test_ip_fast_csum
0x83da is the expected result if the IP header length is 20 bytes. 0x2ac2
is the expected result if the IP header length is 24 bytes. The test fails
with an IP header length of 24 bytes. It appears that ip_fast_csum()
always returns the checksum for a 20-byte header, no matter how long
the header actually is.
Code analysis shows a suspicious assembler sequence in ip_fast_csum().
" addc %0, %3, %0\n"
"1: ldws,ma 4(%1), %3\n"
" addib,< 0, %2, 1b\n" <---
While my understanding of HPPA assembler is limited, it does not seem
to make much sense to subtract 0 from a register and to expect the result
to ever be negative. Subtracting 1 from the length parameter makes more
sense. On top of that, the operation should be repeated if and only if
the result is still > 0, so change the suspicious instruction to
" addib,> -1, %2, 1b\n"
The IP checksum unit test passes after this change.
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Tested-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
Reviewed-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/parisc/include/asm/checksum.h b/arch/parisc/include/asm/checksum.h
index 3c43baca7b397..f705e5dd10742 100644
--- a/arch/parisc/include/asm/checksum.h
+++ b/arch/parisc/include/asm/checksum.h
@@ -40,7 +40,7 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
" addc %0, %5, %0\n"
" addc %0, %3, %0\n"
"1: ldws,ma 4(%1), %3\n"
-" addib,< 0, %2, 1b\n"
+" addib,> -1, %2, 1b\n"
" addc %0, %3, %0\n"
"\n"
" extru %0, 31, 16, %4\n"
