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From: Waiman Long <longman@redhat.com>
To: Joe Perches <joe@perches.com>,
	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>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	David Sterba <dsterba@suse.cz>,
	"Jason A . Donenfeld" <Jason@zx2c4.com>,
	linux-mm@kvack.org, keyrings@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
	linux-pm@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-amlogic@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org,
	virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, linux-ppp@vger.kernel.org,
	wireguard@lists.zx2c4.com, linux-wireless@vger.kernel.org,
	devel@driverdev.osuosl.org, linux-scsi@vger.kernel.org,
	target-devel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	linux-cifs@vger.kernel.org, linux-fscrypt@vger.kernel.org,
	ecryptfs@vger.kernel.org, kasan-dev@googlegroups.com,
	linux-bluetooth@vger.kernel.org, linux-wpan@vger.kernel.org,
	linux-sctp@vger.kernel.org, linux-nfs@vger.kernel.org,
	tipc-discussion@lists.sourceforge.net,
	linux-security-module@vger.kernel.org,
	linux-integrity@vger.kernel.org
Subject: Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive()
Date: Tue, 16 Jun 2020 15:43:16 -0400
Message-ID: <5c70746c-ecfc-316f-f1ff-ab432cf9f32d@redhat.com> (raw)
In-Reply-To: <fe3b9a437be4aeab3bac68f04193cb6daaa5bee4.camel@perches.com>

On 6/16/20 2:53 PM, Joe Perches wrote:
> On Mon, 2020-06-15 at 21:57 -0400, Waiman Long wrote:
>>   v4:
>>    - Break out the memzero_explicit() change as suggested by Dan Carpenter
>>      so that it can be backported to stable.
>>    - Drop the "crypto: Remove unnecessary memzero_explicit()" patch for
>>      now as there can be a bit more discussion on what is best. It will be
>>      introduced as a separate patch later on after this one is merged.
> To this larger audience and last week without reply:
> https://lore.kernel.org/lkml/573b3fbd5927c643920e1364230c296b23e7584d.camel@perches.com/
>
> Are there _any_ fastpath uses of kfree or vfree?

I am not sure about that, but both of them can be slow.


>
> Many patches have been posted recently to fix mispairings
> of specific types of alloc and free functions.
>
> To eliminate these mispairings at a runtime cost of four
> comparisons, should the kfree/vfree/kvfree/kfree_const
> functions be consolidated into a single kfree?
>
> Something like the below:
>
>     void kfree(const void *addr)
>     {
>     	if (is_kernel_rodata((unsigned long)addr))
>     		return;
>
>     	if (is_vmalloc_addr(addr))
>     		_vfree(addr);
>     	else
>     		_kfree(addr);
>     }
>
is_kernel_rodata() is inlined, but is_vmalloc_addr() isn't. So the 
overhead can be a bit bigger.

Cheers,
Longman


  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-16  1:57 Waiman Long
2020-06-16  1:57 ` [PATCH v4 1/3] mm/slab: Use memzero_explicit() in kzfree() Waiman Long
2020-06-16  3:30   ` Eric Biggers
2020-06-16 13:05     ` Waiman Long
2020-06-16 15:46     ` David Howells
2020-06-16  6:42   ` Michal Hocko
2020-06-16  9:08     ` Dan Carpenter
2020-06-16  1:57 ` [PATCH v4 2/3] mm, treewide: Rename kzfree() to kfree_sensitive() Waiman Long
2020-06-16 14:26   ` Dan Carpenter
2020-06-16 15:05     ` Waiman Long
2020-06-16  1:57 ` [PATCH v4 3/3] btrfs: Use kfree() in btrfs_ioctl_get_subvol_info() Waiman Long
2020-06-16 14:48   ` David Sterba
2020-06-16 15:05     ` Waiman Long
2020-06-16 18:53 ` [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive() Joe Perches
2020-06-16 19:43   ` Waiman Long [this message]
2020-06-16 19:46   ` Jason A. Donenfeld
2020-06-16 20:01   ` Waiman Long
2020-06-16 21:14   ` Matthew Wilcox
2020-06-16 23:01   ` David Sterba
2020-06-17  0:37     ` Matthew Wilcox
2020-06-17  7:12       ` Michal Hocko
2020-06-17 11:08         ` Matthew Wilcox
2020-06-17 11:31           ` Michal Hocko
2020-06-17 12:23             ` Matthew Wilcox
2020-06-17 12:55               ` Michal Hocko
2020-06-17  8:03       ` Jo -l
2020-06-17 21:31   ` Denis Efremov
2020-06-17 23:12     ` Joe Perches

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