This is a note to let you know that I've just added the patch titled
ARM: 9321/1: memset: cast the constant byte to unsigned char
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:
arm-9321-1-memset-cast-the-constant-byte-to-unsigned.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 f71e01feff5b06f29dea7be9408bbe282c83427a
Author: Kursad Oney <kursad.oney@xxxxxxxxxxxx>
Date: Tue Aug 22 15:06:06 2023 +0100
ARM: 9321/1: memset: cast the constant byte to unsigned char
[ Upstream commit c0e824661f443b8cab3897006c1bbc69fd0e7bc4 ]
memset() description in ISO/IEC 9899:1999 (and elsewhere) says:
The memset function copies the value of c (converted to an
unsigned char) into each of the first n characters of the
object pointed to by s.
The kernel's arm32 memset does not cast c to unsigned char. This results
in the following code to produce erroneous output:
char a[128];
memset(a, -128, sizeof(a));
This is because gcc will generally emit the following code before
it calls memset() :
mov r0, r7
mvn r1, #127 ; 0x7f
bl 00000000 <memset>
r1 ends up with 0xffffff80 before being used by memset() and the
'a' array will have -128 once in every four bytes while the other
bytes will be set incorrectly to -1 like this (printing the first
8 bytes) :
test_module: -128 -1 -1 -1
test_module: -1 -1 -1 -128
The change here is to 'and' r1 with 255 before it is used.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reviewed-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Kursad Oney <kursad.oney@xxxxxxxxxxxx>
Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm/lib/memset.S b/arch/arm/lib/memset.S
index 9817cb258c1a5..0481b9bbbd004 100644
--- a/arch/arm/lib/memset.S
+++ b/arch/arm/lib/memset.S
@@ -17,6 +17,7 @@ ENTRY(__memset)
ENTRY(mmioset)
WEAK(memset)
UNWIND( .fnstart )
+ and r1, r1, #255 @ cast to unsigned char
ands r3, r0, #3 @ 1 unaligned?
mov ip, r0 @ preserve r0 as return value
bne 6f @ 1
