From: Waiman Long <longman@xxxxxxxxxx> commit 8982ae527fbef170ef298650c15d55a9ccd33973 upstream. 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@xxxxxxxxxx Fixes: 3ef0e5ba4673 ("slab: introduce kzfree()") Signed-off-by: Waiman Long <longman@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: David Howells <dhowells@xxxxxxxxxx> Cc: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> Cc: James Morris <jmorris@xxxxxxxxx> Cc: "Serge E. Hallyn" <serge@xxxxxxxxxx> Cc: Joe Perches <joe@xxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Cc: "Jason A . Donenfeld" <Jason@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/slab_common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index 13f1926f8fcd4..26c4d47229273 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1345,7 +1345,7 @@ 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); -- 2.25.1
