From: Kursad Oney Date: Tue, 22 Aug 2023 14:06:06 +0000 (+0100) Subject: ARM: 9321/1: memset: cast the constant byte to unsigned char X-Git-Tag: v6.6.7~1263 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=7c8ad76067f85c84b1e980356f56d0aaaf2df86f;p=platform%2Fkernel%2Flinux-starfive.git 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 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 Reviewed-by: Linus Walleij Signed-off-by: Kursad Oney Signed-off-by: Russell King (Oracle) Signed-off-by: Sasha Levin --- diff --git a/arch/arm/lib/memset.S b/arch/arm/lib/memset.S index d71ab61..de75ae4 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