From: Josh Poimboeuf <jpoimboe@redhat.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: "x86@kernel.org" <x86@kernel.org>,
Andrey Konovalov <andreyknvl@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Vlad Yasevich <vyasevich@gmail.com>,
Neil Horman <nhorman@tuxdriver.com>,
"David S . Miller" <davem@davemloft.net>,
"linux-sctp@vger.kernel.org" <linux-sctp@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Kostya Serebryany <kcc@google.com>,
syzkaller <syzkaller@googlegroups.com>,
Eric Dumazet <edumazet@google.com>,
Cong Wang <xiyou.wangcong@gmail.com>
Subject: Re: [PATCH] x86/asm: Don't use rbp as temp register in csum_partial_copy_generic()
Date: Thu, 4 May 2017 11:11:29 -0500 [thread overview]
Message-ID: <20170504161129.syz46qyxge3nupki@treble> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6DCFFE581C@AcuExch.aculab.com>
On Thu, May 04, 2017 at 03:56:49PM +0000, David Laight wrote:
> From: Josh Poimboeuf
> > Sent: 04 May 2017 15:52
> > Andrey Konovalov reported the following warning while fuzzing the kernel
> > with syzkaller:
> >
> > WARNING: kernel stack regs at ffff8800686869f8 in a.out:4933 has bad 'bp' value c3fc855a10167ec0
> >
> > The unwinder dump revealed that rbp had a bad value when an interrupt
> > occurred in csum_partial_copy_generic().
> >
> > That function saves rbp on the stack and then overwrites it, using it as
> > a scratch register. That's problematic because it breaks stack traces
> > if an interrupt occurs in the middle of the function.
>
> Does gcc guarantee not to use bp as a scratch register in leaf functions?
At least in practice, gcc doesn't touch rbp in leaf functions. (I don't
know about guarantees.)
--
Josh
next prev parent reply other threads:[~2017-05-04 16:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-04 14:51 [PATCH] x86/asm: Don't use rbp as temp register in csum_partial_copy_generic() Josh Poimboeuf
2017-05-04 15:56 ` David Laight
2017-05-04 16:11 ` Josh Poimboeuf [this message]
2017-05-05 8:10 ` [tip:x86/urgent] x86/asm: Don't use RBP as a temporary " tip-bot for Josh Poimboeuf
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