linux-kernel - Re: [PATCH] arm: memset: zero out upper bytes in r1

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 8 May 2014 08:04:44 +0000 (UTC)
From:	Vladimir Murzin <murzin.v@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm: memset: zero out upper bytes in r1

Andrey Ryabinin <a.ryabinin <at> samsung.com> writes:

> 
> memset doesn't work right for following example:
> 
> 	signed char c = 0xF0;
> 	memset(addr, c, size);
> 
> Variable c is signed, so after typcasting to int the value will be 0xFFFFFFF0.
> This value will be passed through r1 regitster to memset function.
> memset doesn't zero out upper bytes in r1, so memory will be filled
> with 0xFFFFFFF0 instead of expected 0xF0F0F0F0.

It behaves the same as a generic implementation in lib/string.c, moreover
gcc built-in behaves the same. So it looks like expected behavior and POSIX
Programmer's Manual (man 3posix memset) explicitly says that "c" is
converted to unsigned char.

Cheers
Vladimir

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/