| Message ID | CAM_iQpWG1Otj7FU_TcZqEt9kEuNYU0ihkPyXeCQQEBNUhwnoCw@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Apr 10, 2017 at 11:07 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote: > On Mon, Apr 10, 2017 at 7:37 AM, Andrey Konovalov <andreyknvl@google.com> wrote: >> Hi, >> >> I've got the following error report while fuzzing the kernel with syzkaller. >> >> On commit 39da7c509acff13fc8cb12ec1bb20337c988ed36 (4.11-rc6). >> >> Unfortunately it's not reproducible. >> >> ================================================================== >> BUG: KASAN: use-after-free in __read_once_size >> include/linux/compiler.h:254 [inline] at addr ffff880059ce6590 >> BUG: KASAN: use-after-free in atomic_read >> arch/x86/include/asm/atomic.h:26 [inline] at addr ffff880059ce6590 >> BUG: KASAN: use-after-free in virt_spin_lock >> arch/x86/include/asm/qspinlock.h:62 [inline] at addr ffff880059ce6590 >> BUG: KASAN: use-after-free in queued_spin_lock_slowpath+0xb0a/0xfd0 >> kernel/locking/qspinlock.c:421 at addr ffff880059ce6590 >> Read of size 4 by task syz-executor6/567 >> CPU: 1 PID: 567 Comm: syz-executor6 Not tainted 4.11.0-rc6+ #206 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:16 [inline] >> dump_stack+0x292/0x398 lib/dump_stack.c:52 >> kasan_object_err+0x1c/0x70 mm/kasan/report.c:164 >> print_address_description mm/kasan/report.c:202 [inline] >> kasan_report_error mm/kasan/report.c:291 [inline] >> kasan_report+0x252/0x510 mm/kasan/report.c:347 >> __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:367 >> __read_once_size include/linux/compiler.h:254 [inline] >> atomic_read arch/x86/include/asm/atomic.h:26 [inline] >> virt_spin_lock arch/x86/include/asm/qspinlock.h:62 [inline] >> queued_spin_lock_slowpath+0xb0a/0xfd0 kernel/locking/qspinlock.c:421 >> queued_spin_lock include/asm-generic/qspinlock.h:103 [inline] >> do_raw_spin_lock+0x151/0x1e0 kernel/locking/spinlock_debug.c:113 >> __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline] >> _raw_spin_lock+0x32/0x40 kernel/locking/spinlock.c:151 >> spin_lock include/linux/spinlock.h:299 [inline] >> lockref_get_not_dead+0x19/0x80 lib/lockref.c:179 >> __ns_get_path+0x197/0x860 fs/nsfs.c:66 > > This is almost not related to net, it is almost a pure fs bug. > So let's Cc Al. Al, ping. > I think the following one-line fix should work, since > ns->stashed is protected by RCU on the fast path, but > I am not brave enough to add a new dcache API for it. ;) > > diff --git a/fs/nsfs.c b/fs/nsfs.c > index 1656843..ecfd3d1 100644 > --- a/fs/nsfs.c > +++ b/fs/nsfs.c > @@ -90,6 +90,7 @@ static void *__ns_get_path(struct path *path, struct > ns_common *ns) > iput(inode); > return ERR_PTR(-ENOMEM); > } > + dentry->d_flags |= DCACHE_RCUACCESS; > d_instantiate(dentry, inode); > dentry->d_fsdata = (void *)ns->ops; > d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); > > > >> open_related_ns+0xda/0x200 fs/nsfs.c:143 >> sock_ioctl+0x39d/0x440 net/socket.c:1001 >> vfs_ioctl fs/ioctl.c:45 [inline] >> do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:685 >> SYSC_ioctl fs/ioctl.c:700 [inline] >> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691 >> entry_SYSCALL_64_fastpath+0x1f/0xc2 >> RIP: 0033:0x4458d9 >> RSP: 002b:00007f1c9259eb58 EFLAGS: 00000286 ORIG_RAX: 0000000000000010 >> RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 00000000004458d9 >> RDX: 000000002090affc RSI: 000000000000894c RDI: 0000000000000016 >> RBP: 00000000006e1c50 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000708150 >> R13: 0000000000000000 R14: 00007f1c9259f9c0 R15: 00007f1c9259f700 >> Object at ffff880059ce6510, in cache dentry size: 288 >> Allocated: >> PID = 565 >> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 >> save_stack+0x43/0xd0 mm/kasan/kasan.c:513 >> set_track mm/kasan/kasan.c:525 [inline] >> kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616 >> kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:555 >> slab_post_alloc_hook mm/slab.h:456 [inline] >> slab_alloc_node mm/slub.c:2718 [inline] >> slab_alloc mm/slub.c:2726 [inline] >> kmem_cache_alloc+0x1af/0x250 mm/slub.c:2731 >> __d_alloc+0xb3/0xbd0 fs/dcache.c:1571 >> d_alloc_pseudo+0x1d/0x30 fs/dcache.c:1692 >> __ns_get_path+0x3e8/0x860 fs/nsfs.c:88 >> open_related_ns+0xda/0x200 fs/nsfs.c:143 >> sock_ioctl+0x39d/0x440 net/socket.c:1001 >> vfs_ioctl fs/ioctl.c:45 [inline] >> do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:685 >> SYSC_ioctl fs/ioctl.c:700 [inline] >> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691 >> entry_SYSCALL_64_fastpath+0x1f/0xc2 >> Freed: >> PID = 566 >> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 >> save_stack+0x43/0xd0 mm/kasan/kasan.c:513 >> set_track mm/kasan/kasan.c:525 [inline] >> kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:589 >> slab_free_hook mm/slub.c:1357 [inline] >> slab_free_freelist_hook mm/slub.c:1379 [inline] >> slab_free mm/slub.c:2961 [inline] >> kmem_cache_free+0xb2/0x2c0 mm/slub.c:2983 >> __d_free fs/dcache.c:265 [inline] >> dentry_free+0xd5/0x150 fs/dcache.c:314 >> __dentry_kill+0x485/0x6e0 fs/dcache.c:552 >> dentry_kill fs/dcache.c:579 [inline] >> dput.part.25+0x5cd/0x7c0 fs/dcache.c:791 >> dput+0x1f/0x30 fs/dcache.c:753 >> __fput+0x527/0x7f0 fs/file_table.c:227 >> ____fput+0x15/0x20 fs/file_table.c:245 >> task_work_run+0x19b/0x270 kernel/task_work.c:116 >> tracehook_notify_resume include/linux/tracehook.h:191 [inline] >> exit_to_usermode_loop+0x1c2/0x200 arch/x86/entry/common.c:161 >> prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline] >> syscall_return_slowpath+0x3d3/0x420 arch/x86/entry/common.c:260 >> entry_SYSCALL_64_fastpath+0xc0/0xc2 >> Memory state around the buggy address: >> ffff880059ce6480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ffff880059ce6500: fc fc fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>>ffff880059ce6580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ^ >> ffff880059ce6600: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc >> ffff880059ce6680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ==================================================================
On Mon, May 29, 2017 at 04:46:23PM +0200, Dmitry Vyukov wrote:
> Al, ping.
See commit 073c516ff735. Can you still trigger that on the
current mainline?
diff --git a/fs/nsfs.c b/fs/nsfs.c index 1656843..ecfd3d1 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -90,6 +90,7 @@ static void *__ns_get_path(struct path *path, struct ns_common *ns) iput(inode); return ERR_PTR(-ENOMEM); } + dentry->d_flags |= DCACHE_RCUACCESS; d_instantiate(dentry, inode); dentry->d_fsdata = (void *)ns->ops;