linux-kernel - Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200617110820.GG8681@bombadil.infradead.org>
Date:   Wed, 17 Jun 2020 04:08:20 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     dsterba@...e.cz, Joe Perches <joe@...ches.com>,
        Waiman Long <longman@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>, linux-mm@...ck.org,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-amlogic@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-ppp@...r.kernel.org, wireguard@...ts.zx2c4.com,
        linux-wireless@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-cifs@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, ecryptfs@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-bluetooth@...r.kernel.org,
        linux-wpan@...r.kernel.org, linux-sctp@...r.kernel.org,
        linux-nfs@...r.kernel.org, tipc-discussion@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org
Subject: Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive()

On Wed, Jun 17, 2020 at 09:12:12AM +0200, Michal Hocko wrote:
> On Tue 16-06-20 17:37:11, Matthew Wilcox wrote:
> > Not just performance critical, but correctness critical.  Since kvfree()
> > may allocate from the vmalloc allocator, I really think that kvfree()
> > should assert that it's !in_atomic().  Otherwise we can get into trouble
> > if we end up calling vfree() and have to take the mutex.
> 
> FWIW __vfree already checks for atomic context and put the work into a
> deferred context. So this should be safe. It should be used as a last
> resort, though.

Actually, it only checks for in_interrupt().  If you call vfree() under
a spinlock, you're in trouble.  in_atomic() only knows if we hold a
spinlock for CONFIG_PREEMPT, so it's not safe to check for in_atomic()
in __vfree().  So we need the warning in order that preempt people can
tell those without that there is a bug here.