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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 08:47:55 -0800
commit25e1465ac3cfeafce34b3a47e773c4bc950054a3 (patch)
tree31d1c7845bb872d25967f82d253b31b0561bdc1c /lib
parent620c41147d873223d8aac0aa64793882b6217f09 (diff)
downloadlinux-linaro-stable-25e1465ac3cfeafce34b3a47e773c4bc950054a3.tar.gz
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 '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 e5878de4f101..43d0781daf47 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -586,6 +586,22 @@ 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