On Wed, 2019-04-10 at 10:27 +0200, Dmitry Vyukov wrote:
> On Wed, Apr 10, 2019 at 2:26 AM Al Viro <v...@zeniv.linux.org.uk> wrote:
> >
> > 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.
>
> Hi Al,
>
> This is the commit for matching lines:
>
> > HEAD commit: d14b746c6c1c Add linux-next specific files for 20181214
Are you sure?
what does 20181214 mean?
Looking at current next code (and several branches) it doesn't
appear the problem is possible?
> > git tree: linux-next
But which branch is it really, master (which doesn't match the
line numbers btw)?
>
> fs/inode.c:1566 points to:
>
> void iput(struct inode *inode)
> {
> ...
> BUG_ON(inode->i_state & I_CLEAR);
>
>
> The dashboard page provides kernel git repository and commit for each crash.
Those links don't seem to make sense to me ...
Help me out here!
Ian
