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authorDaniel Borkmann <dborkman@redhat.com>2014-08-26 23:16:35 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-11-14 08:59:49 -0800
commitb0bb7fc84dc32cdf506d14caef0144f6a83afd10 (patch)
tree84419fa5ff4ae94793848693631edff963b0b3d9 /drivers/char
parentc8f712403473828d7a72882025114ef42491b1ae (diff)
downloadlwn-b0bb7fc84dc32cdf506d14caef0144f6a83afd10.tar.gz
lwn-b0bb7fc84dc32cdf506d14caef0144f6a83afd10.zip
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 <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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/random.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 429b75bb60e8..8a64dbeae7b1 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1063,8 +1063,8 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
* pool while mixing, and hash one final time.
*/
sha_transform(hash.w, extract, workspace);
- memset(extract, 0, sizeof(extract));
- memset(workspace, 0, sizeof(workspace));
+ memzero_explicit(extract, sizeof(extract));
+ memzero_explicit(workspace, sizeof(workspace));
/*
* In case the hash function has some recognizable output
@@ -1076,7 +1076,7 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
hash.w[2] ^= rol32(hash.w[2], 16);
memcpy(out, &hash, EXTRACT_SIZE);
- memset(&hash, 0, sizeof(hash));
+ memzero_explicit(&hash, sizeof(hash));
}
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
@@ -1124,7 +1124,7 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
}
/* Wipe data just returned from memory */
- memset(tmp, 0, sizeof(tmp));
+ memzero_explicit(tmp, sizeof(tmp));
return ret;
}
@@ -1162,7 +1162,7 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
}
/* Wipe data just returned from memory */
- memset(tmp, 0, sizeof(tmp));
+ memzero_explicit(tmp, sizeof(tmp));
return ret;
}