On Thu, Apr 5, 2018 at 10:36 AM, Steven Whitehouse <swhit...@redhat.com> wrote: > Hi, > > > > On 05/04/18 09:19, Dmitry Vyukov wrote: >> >> On Thu, Apr 5, 2018 at 8:34 AM, Greg KH <gre...@linuxfoundation.org> >> wrote: >>> >>> On Wed, Apr 04, 2018 at 07:02:01PM -0700, syzbot wrote: >>>> >>>> Hello, >>>> >>>> syzbot hit the following crash on upstream commit >>>> 3e968c9f1401088abc9a19ae6ff571644d37a355 (Wed Apr 4 21:19:24 2018 +0000) >>>> Merge tag 'ext4_for_linus' of >>>> git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 >>>> syzbot dashboard link: >>>> https://syzkaller.appspot.com/bug?extid=ff87a28e665c163aa7f5 >>>> >>>> C reproducer: >>>> https://syzkaller.appspot.com/x/repro.c?id=5104666266304512 >>>> syzkaller reproducer: >>>> https://syzkaller.appspot.com/x/repro.syz?id=5683447737614336 >>>> Raw console output: >>>> https://syzkaller.appspot.com/x/log.txt?id=5104818200772608 >>>> Kernel config: >>>> https://syzkaller.appspot.com/x/.config?id=9118669095563550941 >>>> compiler: gcc (GCC) 7.1.1 20170620 >>>> >>>> IMPORTANT: if you fix the bug, please add the following tag to the >>>> commit: >>>> Reported-by: syzbot+ff87a28e665c163aa...@syzkaller.appspotmail.com >>>> It will help syzbot understand when the bug is fixed. See footer for >>>> details. >>>> If you forward the report, please keep this part and the footer. >>>> >>>> R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000000003 >>>> R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000000 >>>> ------------[ cut here ]------------ >>>> kobject_add_internal failed for nodev( with -EEXIST, don't try to >>>> register >>>> things with the same name in the same directory. >>>> sysfs: cannot create duplicate filename '/fs/gfs2/nodev(' >>>> WARNING: CPU: 1 PID: 4473 at lib/kobject.c:238 >>>> kobject_add_internal+0x8d4/0xbc0 lib/kobject.c:235 >>>> CPU: 0 PID: 4474 Comm: syzkaller533472 Not tainted 4.16.0+ #15 >>>> Kernel panic - not syncing: panic_on_warn set ... >>>> >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >>>> Google 01/01/2011 >>>> Call Trace: >>>> __dump_stack lib/dump_stack.c:17 [inline] >>>> dump_stack+0x1a7/0x27d lib/dump_stack.c:53 >>>> sysfs_warn_dup+0x83/0xa0 fs/sysfs/dir.c:30 >>>> sysfs_create_dir_ns+0x178/0x1d0 fs/sysfs/dir.c:58 >>>> create_dir lib/kobject.c:69 [inline] >>>> kobject_add_internal+0x335/0xbc0 lib/kobject.c:227 >>>> kobject_add_varg lib/kobject.c:364 [inline] >>>> kobject_init_and_add+0xf9/0x150 lib/kobject.c:436 >>>> gfs2_sys_fs_add+0x1ff/0x580 fs/gfs2/sys.c:652 >>>> fill_super+0x86f/0x1d70 fs/gfs2/ops_fstype.c:1118 >>>> gfs2_mount+0x587/0x6e0 fs/gfs2/ops_fstype.c:1321 >>> >>> gfs2 bug, not a sysfs bug, we are correctly warning about an incorrect >>> usage of the api. >> >> Then +gfs2 maintainers. >> >>> Now if we should turn this into a non-WARN message, that's a different >>> thing, I'll gladly take a patch for that. >> >> If it's API usage bug in higher level code, then I think WARN is a >> proper thing. We already had similar ones and they were fixed. > > > I'm trying to figure out what the test is doing, but it is not very clear. > At a guess I'd say that perhaps it is trying to mount multiple filesystems > with the same label? If that is the case then it is not allowed, and it > should be caught be the sysfs code and result in a refusal to mount, which > is what I think I see here. Knowing which sysfs directory is involved would > allow us to confirm, but I suspect that the test needs altering to give each > gfs2 mount a different label at an initial guess,
Hi Steve, But Greg claims that this is incorrect usage of sysfs API: > gfs2 bug, not a sysfs bug, we are correctly warning about an incorrect > usage of the api. I think this means that sysfs callers must not try to create the same thing twice. Either way user-space code must not be able to triggers WARNINGs in kernel. If it does than this is something to fix in kernel.
