From: Waiman Long longman@redhat.com Subject: 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: 3ef0e5ba4673 ("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 ---
mm/slab_common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/slab_common.c~mm-slab-use-memzero_explicit-in-kzfree +++ a/mm/slab_common.c @@ -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); _