From: Waiman Long <longman@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Howells <dhowells@redhat.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
linux-mm@kvack.org, keyrings@vger.kernel.org,
linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] mm: Add kvfree_sensitive() for freeing sensitive data objects
Date: Mon, 6 Apr 2020 10:36:07 -0400 [thread overview]
Message-ID: <3f6658e5-0082-7759-1d08-eda9cb3eba2f@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.21.2004052119530.243304@chino.kir.corp.google.com>
On 4/6/20 12:20 AM, David Rientjes wrote:
> On Sun, 5 Apr 2020, Waiman Long wrote:
>
>> For kvmalloc'ed data object that contains sensitive information like
>> cryptographic key, we need to make sure that the buffer is always
>> cleared before freeing it. Using memset() alone for buffer clearing may
>> not provide certainty as the compiler may compile it away. To be sure,
>> the special memzero_explicit() has to be used.
>>
>> This patch introduces a new kvfree_sensitive() for freeing those
>> sensitive data objects allocated by kvmalloc(). The relevnat places
>> where kvfree_sensitive() can be used are modified to use it.
>>
>> Fixes: 4f0882491a14 ("KEYS: Avoid false positive ENOMEM error on key read")
>> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
>> Signed-off-by: Waiman Long <longman@redhat.com>
>> ---
>> include/linux/mm.h | 17 +++++++++++++++++
>> security/keys/internal.h | 11 -----------
>> security/keys/keyctl.c | 16 +++++-----------
>> 3 files changed, 22 insertions(+), 22 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 7dd5c4ccbf85..c26f279f1956 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -758,6 +758,23 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
>>
>> extern void kvfree(const void *addr);
>>
>> +/**
>> + * kvfree_sensitive - free a data object containing sensitive information
>> + * @addr - address of the data object to be freed
>> + * @len - length of the data object
>> + *
>> + * Use the special memzero_explicit() function to clear the content of a
>> + * kvmalloc'ed object containing sensitive data to make sure that the
>> + * compiler won't optimize out the data clearing.
>> + */
>> +static inline void kvfree_sensitive(const void *addr, size_t len)
>> +{
>> + if (addr) {
> Shouldn't this be if (unlikely(ZERO_OR_NULL_PTR(addr))?
>
ZERO_OR_NULL_PTR is defined in slab.h. Using it may cause some header
file dependency problem. To guard against the possibility of 0-length
allocation request, how about just
if (likely(addr && len)) {
Cheers,
Longman
next prev parent reply other threads:[~2020-04-06 14:36 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-06 2:37 [PATCH] mm: Add kvfree_sensitive() for freeing sensitive data objects Waiman Long
2020-04-06 4:20 ` David Rientjes
2020-04-06 14:36 ` Waiman Long [this message]
2020-04-06 14:39 ` Matthew Wilcox
2020-04-06 7:44 ` David Howells
2020-04-06 23:20 ` David Rientjes
2020-04-06 14:32 ` David Howells
2020-04-06 14:40 ` Waiman Long
2020-04-06 15:45 ` Joe Perches
2020-04-06 16:00 ` David Howells
2020-04-06 16:10 ` Joe Perches
2020-04-06 16:41 ` Linus Torvalds
2020-04-06 16:42 ` Joe Perches
2020-04-06 17:11 ` Linus Torvalds
2020-04-06 17:20 ` Joe Perches
2020-04-06 17:26 ` Matthew Wilcox
2020-04-06 17:33 ` Linus Torvalds
2020-04-06 17:46 ` Joe Perches
2020-04-06 17:58 ` Waiman Long
2020-04-06 18:06 ` Linus Torvalds
2020-04-06 18:46 ` Joe Perches
2020-04-06 16:26 ` David Howells
2020-04-06 16:38 ` Joe Perches
2020-04-06 17:10 ` Joe Perches
2020-04-06 17:24 ` Matthew Wilcox
2020-04-06 17:26 ` Linus Torvalds
2020-04-06 17:51 ` David Howells
2020-04-06 17:58 ` Linus Torvalds
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