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| author | Daniel Borkmann <dborkman@redhat.com> | 2014-08-27 07:16:35 +0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2014-10-17 19:37:29 +0400 |
| commit | d4c5efdb97773f59a2b711754ca0953f24516739 (patch) | |
| tree | 83ededeb92d6d529e8081b97b2f9cdf491094b78 /lib | |
| parent | 7d1311b93e58ed55f3a31cc8f94c4b8fe988a2b9 (diff) | |
| download | linux-d4c5efdb97773f59a2b711754ca0953f24516739.tar.xz | |
random: add and use memzero_explicit() for clearing data
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 <dborkman@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/string.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/lib/string.c b/lib/string.c index 992bf30af759..3a3120452a1d 100644 --- a/lib/string.c +++ b/lib/string.c @@ -604,6 +604,22 @@ void *memset(void *s, int c, size_t count) EXPORT_SYMBOL(memset); #endif +/** + * memzero_explicit - Fill a region of memory (e.g. sensitive + * keying data) with 0s. + * @s: Pointer to the start of the area. + * @count: The size of the area. + * + * memzero_explicit() doesn't need an arch-specific version as + * it just invokes the one of memset() implicitly. + */ +void memzero_explicit(void *s, size_t count) +{ + memset(s, 0, count); + OPTIMIZER_HIDE_VAR(s); +} +EXPORT_SYMBOL(memzero_explicit); + #ifndef __HAVE_ARCH_MEMCPY /** * memcpy - Copy one area of memory to another |