From: Waiman Long <longman@xxxxxxxxxx> 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@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> --- 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); _
