From 2bdb21fe06c81e977e2bcf1ad3063ba96db9563f Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 26 Aug 2014 23:16:35 -0400 Subject: random: add and use memzero_explicit() for clearing data 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 --- include/linux/string.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/string.h b/include/linux/string.h index e033564f10ba..8515a4dbc1c9 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -144,5 +144,7 @@ static inline bool strstarts(const char *str, const char *prefix) { return strncmp(str, prefix, strlen(prefix)) == 0; } + +void memzero_explicit(void *s, size_t count); #endif #endif /* _LINUX_STRING_H_ */ -- cgit v1.2.3