user/sven/linux.git/lib/string.c, branch v3.2.97

lib: memzero_explicit: use barrier instead of OPTIMIZER_HIDE_VAR

2015-08-06T23:32:00Z

commit 0b053c9518292705736329a8fe20ef4686ffc8e9 upstream. OPTIMIZER_HIDE_VAR(), as defined when using gcc, is insufficient to ensure protection from dead store optimization. For the random driver and crypto drivers, calls are emitted ... $ gdb vmlinux (gdb) disassemble memzero_explicit Dump of assembler code for function memzero_explicit: 0xffffffff813a18b0 <+0>: push %rbp 0xffffffff813a18b1 <+1>: mov %rsi,%rdx 0xffffffff813a18b4 <+4>: xor %esi,%esi 0xffffffff813a18b6 <+6>: mov %rsp,%rbp 0xffffffff813a18b9 <+9>: callq 0xffffffff813a7120 0xffffffff813a18be <+14>: pop %rbp 0xffffffff813a18bf <+15>: retq End of assembler dump. (gdb) disassemble extract_entropy [...] 0xffffffff814a5009 <+313>: mov %r12,%rdi 0xffffffff814a500c <+316>: mov $0xa,%esi 0xffffffff814a5011 <+321>: callq 0xffffffff813a18b0 0xffffffff814a5016 <+326>: mov -0x48(%rbp),%rax [...] ... but in case in future we might use facilities such as LTO, then OPTIMIZER_HIDE_VAR() is not sufficient to protect gcc from a possible eviction of the memset(). We have to use a compiler barrier instead. Minimal test example when we assume memzero_explicit() would *not* be a call, but would have been *inlined* instead: static inline void memzero_explicit(void *s, size_t count) { memset(s, 0, count); } int main(void) { char buff[20]; snprintf(buff, sizeof(buff) - 1, "test"); printf("%s", buff); memzero_explicit(buff, sizeof(buff)); return 0; } With := OPTIMIZER_HIDE_VAR(): (gdb) disassemble main Dump of assembler code for function main: [...] 0x0000000000400464 <+36>: callq 0x400410 0x0000000000400469 <+41>: xor %eax,%eax 0x000000000040046b <+43>: add $0x28,%rsp 0x000000000040046f <+47>: retq End of assembler dump. With := barrier(): (gdb) disassemble main Dump of assembler code for function main: [...] 0x0000000000400464 <+36>: callq 0x400410 0x0000000000400469 <+41>: movq $0x0,(%rsp) 0x0000000000400471 <+49>: movq $0x0,0x8(%rsp) 0x000000000040047a <+58>: movl $0x0,0x10(%rsp) 0x0000000000400482 <+66>: xor %eax,%eax 0x0000000000400484 <+68>: add $0x28,%rsp 0x0000000000400488 <+72>: retq End of assembler dump. As can be seen, movq, movq, movl are being emitted inlined via memset(). Reference: http://thread.gmane.org/gmane.linux.kernel.cryptoapi/13764/ Fixes: d4c5efdb9777 ("random: add and use memzero_explicit() for clearing data") Cc: Theodore Ts'o Signed-off-by: mancha security Signed-off-by: Daniel Borkmann Acked-by: Hannes Frederic Sowa Acked-by: Stephan Mueller Signed-off-by: Herbert Xu Signed-off-by: Ben Hutchings

random: add and use memzero_explicit() for clearing data

2014-12-14T16:23:49Z

commit d4c5efdb97773f59a2b711754ca0953f24516739 upstream. zatimend has reported that in his environment (3.16/gcc4.8.3/corei7) memset() calls which clear out sensitive data in extract_{buf,entropy, entropy_user}() in random driver are being optimized away by gcc. Add a helper memzero_explicit() (similarly as explicit_bzero() variants) that can be used in such cases where a variable with sensitive data is being cleared out in the end. Other use cases might also be in crypto code. [ I have put this into lib/string.c though, as it's always built-in and doesn't need any dependencies then. ] Fixes kernel bugzilla: 82041 Reported-by: zatimend@hotmail.co.uk Signed-off-by: Daniel Borkmann Acked-by: Hannes Frederic Sowa Cc: Alexey Dobriyan Signed-off-by: Theodore Ts'o [bwh: Backported to 3.2: - extract_buf() needs to use this for the 'extract' array as well - Adjust context] Signed-off-by: Ben Hutchings

lib/string.c: fix strim() semantics for strings that have only blanks

2011-11-01T00:30:56Z

Commit 84c95c9acf0 ("string: on strstrip(), first remove leading spaces before running over str") improved the performance of the strim() function. Unfortunately this changed the semantics of strim() and broke my code. Before the patch it was possible to use strim() without using the return value for removing trailing spaces from strings that had either only blanks or only trailing blanks. Now this does not work any longer for strings that *only* have blanks. Before patch: " " -> "" (empty string) After patch: " " -> " " (no change) I think we should remove your patch to restore the old behavior. The description (lib/string.c): * Note that the first trailing whitespace is replaced with a %NUL-terminator => The first trailing whitespace of a string that only has whitespace characters is the first whitespace The patch restores the old strim() semantics. Signed-off-by: Michael Holzheu Cc: Andre Goddard Rosa Cc: Martin Schwidefsky Cc: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib/string.c: introduce memchr_inv()

2011-11-01T00:30:47Z

memchr_inv() is mainly used to check whether the whole buffer is filled with just a specified byte. The function name and prototype are stolen from logfs and the implementation is from SLUB. Signed-off-by: Akinobu Mita Acked-by: Christoph Lameter Acked-by: Pekka Enberg Cc: Matt Mackall Acked-by: Joern Engel Cc: Marcin Slusarz Cc: Eric Dumazet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Add a strtobool function matching semantics of existing in kernel equivalents

2011-05-19T07:25:28Z

This is a rename of the usr_strtobool proposal, which was a renamed, relocated and fixed version of previous kstrtobool RFC Signed-off-by: Jonathan Cameron Signed-off-by: Rusty Russell

lib/string.c: simplify strnstr()

2010-03-06T19:26:35Z

Signed-off-by: André Goddard Rosa Cc: Li Zefan Cc: Joe Perches Cc: Frederic Weisbecker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib/string.c: simplify stricmp()

2010-03-06T19:26:35Z

Removes 32 bytes on core2 with gcc 4.4.1: text data bss dec hex filename 3196 0 0 3196 c7c lib/string-BEFORE.o 3164 0 0 3164 c5c lib/string-AFTER.o Signed-off-by: André Goddard Rosa Cc: Joe Perches Cc: Frederic Weisbecker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib: Introduce strnstr()

2010-01-15T03:38:09Z

It differs strstr() in that it limits the length to be searched in the first string. Signed-off-by: Li Zefan LKML-Reference: <4B4E8743.6030805@cn.fujitsu.com> Acked-by: Frederic Weisbecker Signed-off-by: Steven Rostedt

lib/string.c: fix kernel-doc warnings

2009-12-22T22:17:55Z

Fix kernel-doc warnings (@arg name) in string.c::skip_spaces(). Warning(lib/string.c:347): No description found for parameter 'str' Warning(lib/string.c:347): Excess function parameter 's' description in 'skip_spaces' Signed-off-by: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Subject: Re: [PATCH] strstrip incorrectly marked __must_check

2009-12-15T16:53:34Z

Recently, We marked strstrip() as must_check. because it was frequently misused and it should be checked. However, we found one exception. scsi/ipr.c intentionally ignore return value of strstrip. Because it wishes to keep the whitespace at the beginning. Thus we need to keep with and without checked whitespace trim function. This patch adds a new strim() and changes ipr.c to use it. [akpm@linux-foundation.org: coding-style fixes] Suggested-by: Alan Cox Signed-off-by: KOSAKI Motohiro Cc: James Bottomley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds