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mm/slab: use memzero_explicit() in kzfree()
commit8982ae527f
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@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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -1449,7 +1449,7 @@ void kzfree(const void *p)
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if (unlikely(ZERO_OR_NULL_PTR(mem)))
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if (unlikely(ZERO_OR_NULL_PTR(mem)))
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return;
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return;
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ks = ksize(mem);
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ks = ksize(mem);
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memset(mem, 0, ks);
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memzero_explicit(mem, ks);
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kfree(mem);
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kfree(mem);
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}
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}
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EXPORT_SYMBOL(kzfree);
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EXPORT_SYMBOL(kzfree);
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