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authorDaniel Borkmann <dborkman@redhat.com>2014-08-26 23:16:35 -0400
committerBen Hutchings <ben@decadent.org.uk>2014-12-14 16:23:49 +0000
commit2bdb21fe06c81e977e2bcf1ad3063ba96db9563f (patch)
tree0dbabf22202517c4a15db4814223314ab4355e39 /lib
parentce2584379f31cfc44bbe770bb78430950a24156e (diff)
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> [bwh: Backported to 3.2: - extract_buf() needs to use this for the 'extract' array as well - Adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'lib')
-rw-r--r--lib/string.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/lib/string.c b/lib/string.c
index dc4a86341f91..40136f6f8ea3 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -583,6 +583,22 @@ 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