From: Al Viro <viro@ZenIV.linux.org.uk>
To: Scott Wood <scottwood@freescale.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
LinuxPPC-dev <linuxppc-dev@lists.ozlabs.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
BOUET Serge <serge.bouet@c-s.fr>,
BARABAN Luc <luc.baraban@c-s.fr>
Subject: Re: Recurring Oops in link_path_walk()
Date: Fri, 20 Nov 2015 21:17:46 +0000 [thread overview]
Message-ID: <20151120211745.GN22011@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1448045920.27264.207.camel@freescale.com>
On Fri, Nov 20, 2015 at 12:58:40PM -0600, Scott Wood wrote:
> > 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.
OK, AFAICS it's this:
604) do {
605) struct path link = *path;
606) void *cookie;
607)
608) res = follow_link(&link, nd, &cookie);
609) if (res)
610) break;
611) res = walk_component(nd, path, LOOKUP_FOLLOW);
612) put_link(nd, &link, cookie);
and we are seeing assorted garbage as link.dentry->d_inode at put_link()
call. What's really interesting, follow_link() has return 0, which means
that it must have passed through
849) *p = dentry->d_inode->i_op->follow_link(dentry, nd);
with
825) struct dentry *dentry = link->dentry;
upstream of that and link as seen by follow_link() is &link as seen by
caller (nested_symlink()); IOW, at that point link.dentry->d_inode used to
be a valid pointer.
Do you have something resembling a reproducer or a chance to get a crash
dump at that point?
next prev parent reply other threads:[~2015-11-20 21:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-20 17:07 Recurring Oops in link_path_walk() Christophe Leroy
2015-11-20 17:56 ` Al Viro
2015-11-20 18:58 ` Scott Wood
2015-11-20 21:17 ` Al Viro [this message]
2015-11-21 10:37 ` christophe leroy
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