4.19-stable review patch. If anyone has any objections, please let me know.
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From: Kursad Oney kursad.oney@broadcom.com
[ 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@kernel.org Reviewed-by: Linus Walleij linus.walleij@linaro.org Signed-off-by: Kursad Oney kursad.oney@broadcom.com Signed-off-by: Russell King (Oracle) rmk+kernel@armlinux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- 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 ed6d35d9cdb5a..a68688f3f3b3d 100644 --- a/arch/arm/lib/memset.S +++ b/arch/arm/lib/memset.S @@ -19,6 +19,7 @@ ENTRY(mmioset) ENTRY(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