From: Al Viro <viro@zeniv.linux.org.uk>
To: syzbot <syzbot+5399ed0832693e29f392@syzkaller.appspotmail.com>
Cc: akpm@linux-foundation.org, amir73il@gmail.com,
dvyukov@google.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, penguin-kernel@i-love.sakura.ne.jp,
raven@themaw.net, syzkaller-bugs@googlegroups.com
Subject: Re: kernel BUG at fs/inode.c:LINE!
Date: Wed, 10 Apr 2019 01:26:03 +0100 [thread overview]
Message-ID: <20190410002603.GS2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <00000000000036a4a9058619dff3@google.com>
On Tue, Apr 09, 2019 at 07:36:00AM -0700, syzbot wrote:
> Bisection is inconclusive: the first bad commit could be any of:
[snip the useless pile]
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15e1fc2b200000
> start commit: [unknown
> git tree: linux-next
> dashboard link: https://syzkaller.appspot.com/bug?extid=5399ed0832693e29f392
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=101032b3400000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16534063400000
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
If I'm not misreading the "crash report" there, it has injected an allocation
failure in dentry allocation in d_make_root() from autofs_fill_super() (
root_inode = autofs_get_inode(s, S_IFDIR | 0755);
root = d_make_root(root_inode);
) which has triggered iput() on the inode passed to d_make_root() (as it ought
to). At which point it stepped into some BUG_ON() in fs/inode.c, but I've
no idea which one it is - line numbers do not match anything in linux-next
or in mainline. Reported line 1566 is
if (inode->i_nlink && (inode->i_state & I_DIRTY_TIME)) {
in all of them; as the matter of fact, the diff in fs/inode.c between
-next and mainline is empty.
There is a BUG_ON() several lines prior, and in 4.20 it used to be line 1566,
so _probably_ that's what it is. With that assumption, it's
BUG_ON(inode->i_state & I_CLEAR);
IOW, we'd got I_CLEAR in the inode passed to d_make_root() there. Which
should not happen - the inode must have come from new_inode(), which
gets it from new_inode_pseudo(), which zeroes ->i_state. And I_CLEAR
is set only in clear_inode(). For autofs inodes that can come only
from autofs_evict_inode(), called as ->evict() from evict_inode().
Which should never ever be called for inode with positive ->i_count...
It might be memory corruption; it might be a dangling inode pointer
somewhere, it might be something else.
To get any further we really need a confirmation of the identity of
triggered BUG_ON().
As an aside, your "sample crash reports" would've been much more useful if
they went with commit SHA1 in question, especially when they contain line
numbers.
next prev parent reply other threads:[~2019-04-10 0:26 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-17 6:11 kernel BUG at fs/inode.c:LINE! syzbot
2018-12-17 7:21 ` Al Viro
2018-12-17 10:08 ` Dmitry Vyukov
2018-12-18 10:40 ` Tetsuo Handa
2018-12-18 10:42 ` Ian Kent
2018-12-18 11:01 ` Amir Goldstein
2018-12-18 11:52 ` Ian Kent
2018-12-18 11:34 ` Ian Kent
2018-12-18 12:27 ` Dmitry Vyukov
2018-12-18 12:42 ` Ian Kent
2018-12-18 13:19 ` Dmitry Vyukov
2018-12-18 14:40 ` Ian Kent
2018-12-18 21:09 ` Andrew Morton
2018-12-19 0:05 ` Ian Kent
2018-12-18 13:51 ` Al Viro
2019-04-09 14:36 ` syzbot
2019-04-10 0:26 ` Al Viro [this message]
2019-04-10 8:27 ` Dmitry Vyukov
2019-04-10 10:35 ` Ian Kent
2019-04-10 11:40 ` Dmitry Vyukov
2019-04-10 11:57 ` Ian Kent
2019-04-10 12:02 ` Dmitry Vyukov
2019-04-10 12:03 ` Dmitry Vyukov
2019-04-10 12:07 ` Ian Kent
2019-04-10 12:11 ` Al Viro
2019-04-10 12:41 ` Dmitry Vyukov
2019-04-11 0:50 ` Ian Kent
2019-04-11 2:22 ` Al Viro
2019-04-12 11:04 ` Dmitry Vyukov
2019-04-12 19:46 ` Eric Biggers
2019-04-12 10:59 ` Dmitry Vyukov
2019-04-12 19:19 ` Al Viro
2019-04-10 12:39 ` Dmitry Vyukov
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