On Wed, Apr 10, 2019 at 2:26 AM Al Viro <viro@xxxxxxxxxxxxxxxxxx> 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 > git tree: linux-next 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.
