6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kursad Oney <kursad.oney@xxxxxxxxxxxx>
[ 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>
---
arch/arm/lib/memset.S | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/lib/memset.S b/arch/arm/lib/memset.S
index d71ab61430b26..de75ae4d5ab41 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
--
2.42.0
