linux-kernel - Re: Recurring Oops in link_path

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]

Date:	Fri, 20 Nov 2015 12:58:40 -0600
From:	Scott Wood <scottwood@...escale.com>
To:	Al Viro <viro@...IV.linux.org.uk>,
	Christophe Leroy <christophe.leroy@....fr>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	LinuxPPC-dev <linuxppc-dev@...ts.ozlabs.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	BOUET Serge <serge.bouet@....fr>,
	"BARABAN Luc" <luc.baraban@....fr>
Subject: Re: Recurring Oops in link_path_walk()

On Fri, 2015-11-20 at 17:56 +0000, Al Viro wrote:
> On Fri, Nov 20, 2015 at 06:07:59PM +0100, Christophe Leroy wrote:
> > Al,
> > 
> > We've been running Kernel 3.18 for several monthes on our embedded
> > boards, and we have a recurring Oops in link_path_walk()
> > It doesn't happen very often (approximatly once every month on one
> > board among a set of 50 boards, never the same board).
> > 
> > Here below is the last oops I got, with kernel 3.18.22. It crashes
> > at address 0xc00b75ac. Here below is the full desassembly of
> > link_path_walk() so that you can see exactly the offending line.
> > 
> > The address it fails at is always the same (link_path_walk+0x414)
> > but the oopsing data address is each time different. I added all
> > Oops I got below after the disassembly (on different sub-versions of
> > 3.18).
> 
> Looks like garbage in dentry->d_inode, assuming that reconstruction of
> the mapping of line numbers to addresses is correct...  Not sure it is,
> though; what's more, just how does LR manage to point to the insn right
> after the call of dput(), of all things?

When "bl dput" is executed, LR gets set to the instruction after the bl. 
 After dput returns, LR still has that value.  Presumably the call to mntput
was skipped via the beq.  Nothing else modifies LR between the dput return and
the faulting address.

-Scott


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/