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authorWaiman Long <longman@redhat.com>2020-06-04 16:48:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-04 19:06:22 -0700
commitd4eaa2837851db2bfed572898bfc17f9a9f9151e (patch)
tree2256caa7e02fc3f9f17507623a87f87ecc347b84 /mm
parentkmap: consolidate kmap_prot definitions (diff)
downloadwireguard-linux-d4eaa2837851db2bfed572898bfc17f9a9f9151e.tar.xz
wireguard-linux-d4eaa2837851db2bfed572898bfc17f9a9f9151e.zip
mm: add kvfree_sensitive() for freeing sensitive data objects
For kvmalloc'ed data object that contains sensitive information like cryptographic keys, we need to make sure that the buffer is always cleared before freeing it. Using memset() alone for buffer clearing may not provide certainty as the compiler may compile it away. To be sure, the special memzero_explicit() has to be used. This patch introduces a new kvfree_sensitive() for freeing those sensitive data objects allocated by kvmalloc(). The relevant places where kvfree_sensitive() can be used are modified to use it. Fixes: 4f0882491a14 ("KEYS: Avoid false positive ENOMEM error on key read") Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Eric Biggers <ebiggers@google.com> Acked-by: David Howells <dhowells@redhat.com> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Cc: James Morris <jmorris@namei.org> Cc: "Serge E. Hallyn" <serge@hallyn.com> Cc: Joe Perches <joe@perches.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: David Rientjes <rientjes@google.com> Cc: Uladzislau Rezki <urezki@gmail.com> Link: http://lkml.kernel.org/r/20200407200318.11711-1-longman@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/util.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c
index fd9efe6bd463..cd62e6fb5318 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -604,6 +604,24 @@ void kvfree(const void *addr)
}
EXPORT_SYMBOL(kvfree);
+/**
+ * kvfree_sensitive - Free a data object containing sensitive information.
+ * @addr: address of the data object to be freed.
+ * @len: length of the data object.
+ *
+ * Use the special memzero_explicit() function to clear the content of a
+ * kvmalloc'ed object containing sensitive data to make sure that the
+ * compiler won't optimize out the data clearing.
+ */
+void kvfree_sensitive(const void *addr, size_t len)
+{
+ if (likely(!ZERO_OR_NULL_PTR(addr))) {
+ memzero_explicit((void *)addr, len);
+ kvfree(addr);
+ }
+}
+EXPORT_SYMBOL(kvfree_sensitive);
+
static inline void *__page_rmapping(struct page *page)
{
unsigned long mapping;