mm/slab: use memzero_explicit() in kzfree()

The kzfree() function is normally used to clear some sensitive
information, like encryption keys, in the buffer before freeing it back to
the pool.  Memset() is currently used for buffer clearing.  However
unlikely, there is still a non-zero probability that the compiler may
choose to optimize away the memory clearing especially if LTO is being
used in the future.

To make sure that this optimization will never happen,
memzero_explicit(), which is introduced in v3.18, is now used in
kzfree() to future-proof it.

Link: http://lkml.kernel.org/r/20200616154311.12314-2-longman@redhat.com
Fixes: 3ef0e5ba46 ("slab: introduce kzfree()")
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: 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: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Jason A . Donenfeld" <Jason@zx2c4.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This commit is contained in:

Waiman Long

2020-06-25 20:29:52 -07:00

committed by

Linus Torvalds

parent d7670879c5

commit 8982ae527f

1 changed files with 1 additions and 1 deletions

									
										2

mm/slab_common.c

										View File
									
				@ -1726,7 +1726,7 @@ void kzfree(const void *p)

					if (unlikely(ZERO_OR_NULL_PTR(mem)))

						return;

					ks = ksize(mem);

					memset(mem, 0, ks);

					memzero_explicit(mem, ks);

					kfree(mem);

				}

				EXPORT_SYMBOL(kzfree);

mm/slab: use memzero_explicit() in kzfree()

2 mm/slab_common.c Unescape Escape View File

2

mm/slab_common.c

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