On Wed, Apr 10, 2019 at 1:57 PM Ian Kent <ra...@themaw.net> 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? > > > > Yes, I just copy-pasted from the report. "d14b746c6c1c" is the commit > > hash. "Add linux-next specific files for 20181214" is the commit > > subject. > > > > > > > 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)? > > > > This is d14b746c6c1c commit hash. I don't know if there is a branch > > with HEAD pointing to this commit or not, but it seems unimportant. > > Tree+commit is the identity of code state. > > > > > > > > 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! > > > > There is git repo name provided and commit hash. It's meant to be > > self-explanatory. What exactly is unclear? > > I'm unable to find a branch matching the line numbers. > > Given that, on the face of it, the scenario is impossible I'm > seeking clarification on what linux-next to look at for the > sake of accuracy. > > So I'm wondering if this testing done using the master branch > or one of the daily branches one would use to check for conflicts > before posting? > > Or perhaps the master branch has been updated and the testing was > done on something different.
Ah, I see. syzbot continuously tests the master branch of linux-next. So d14b746c6c1c was once the HEAD of the master branch. I somehow have d14b746c6c1c locally, but if you don't have it you may need to fetch git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next-history.git with tags. That's linux-next specifics.
