On Tue, Oct 30, 2018 at 08:00:04AM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 11743c56785c Merge tag 'rpmsg-v4.20' of git://github.com/a.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=15121199400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=93932074d01b4a5 > dashboard link: https://syzkaller.appspot.com/bug?extid=3701447012fe951dabb2 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+3701447012fe951dabb2@xxxxxxxxxxxxxxxxxxxxxxxxx > > KASAN: use-after-free Read in del_timer_syncNon-volatile memory driver v1.3 > Linux agpgart interface v0.103 > [drm] Initialized vgem 1.0.0 20120112 for virtual device on minor 0 > usbcore: registered new interface driver udl > ================================================================== > BUG: KASAN: use-after-free in __lock_acquire+0x36d9/0x4c20 > kernel/locking/lockdep.c:3218 > Read of size 8 at addr ffff8801d1b6b540 by task swapper/0/1 > > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.0+ #88 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x244/0x39d lib/dump_stack.c:113 > print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256 > kasan_report_error mm/kasan/report.c:354 [inline] > kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412 > __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 > __lock_acquire+0x36d9/0x4c20 kernel/locking/lockdep.c:3218 > lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844 > del_timer_sync+0xb7/0x270 kernel/time/timer.c:1283 > blk_cleanup_queue+0x413/0x710 block/blk-core.c:809 > brd_free+0x5d/0x71 drivers/block/brd.c:422 > brd_init+0x2eb/0x393 drivers/block/brd.c:518 > do_one_initcall+0x145/0x957 init/main.c:890 > do_initcall_level init/main.c:958 [inline] > do_initcalls init/main.c:966 [inline] > do_basic_setup init/main.c:984 [inline] > kernel_init_freeable+0x5c6/0x6b9 init/main.c:1148 > kernel_init+0x11/0x1ae init/main.c:1068 > ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:350 > > Allocated by task 1: > save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > set_track mm/kasan/kasan.c:460 [inline] > kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 > kmem_cache_alloc_node_trace+0x14c/0x740 mm/slab.c:3663 > kmalloc_node include/linux/slab.h:584 [inline] > bdi_alloc_node+0x89/0xe0 mm/backing-dev.c:861 > blk_alloc_queue_node+0x2b7/0xe80 block/blk-core.c:1024 > blk_alloc_queue+0x1a/0x20 block/blk-core.c:911 > brd_alloc+0xb9/0x540 drivers/block/brd.c:378 > brd_init+0x11d/0x393 drivers/block/brd.c:498 > do_one_initcall+0x145/0x957 init/main.c:890 > do_initcall_level init/main.c:958 [inline] > do_initcalls init/main.c:966 [inline] > do_basic_setup init/main.c:984 [inline] > kernel_init_freeable+0x5c6/0x6b9 init/main.c:1148 > kernel_init+0x11/0x1ae init/main.c:1068 > ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:350 > > Freed by task 12: > save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > set_track mm/kasan/kasan.c:460 [inline] > __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521 > kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 > __cache_free mm/slab.c:3498 [inline] > kfree+0xcf/0x230 mm/slab.c:3817 > release_bdi mm/backing-dev.c:968 [inline] > kref_put include/linux/kref.h:70 [inline] > bdi_put+0x138/0x180 mm/backing-dev.c:973 > blk_exit_queue+0xbf/0xf0 block/blk-core.c:746 > __blk_release_queue+0x12f/0x510 block/blk-sysfs.c:841 > process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153 > worker_thread+0x17f/0x1390 kernel/workqueue.c:2296 > kthread+0x35a/0x440 kernel/kthread.c:246 > ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:350 > > The buggy address belongs to the object at ffff8801d1b6ae80 > which belongs to the cache kmalloc-2k of size 2048 > The buggy address is located 1728 bytes inside of > 2048-byte region [ffff8801d1b6ae80, ffff8801d1b6b680) > The buggy address belongs to the page: > page:ffffea000746da80 count:1 mapcount:0 mapping:ffff8801da800c40 index:0x0 > compound_mapcount: 0 > flags: 0x2fffc0000010200(slab|head) > raw: 02fffc0000010200 ffffea000746da08 ffffea000746dc08 ffff8801da800c40 > raw: 0000000000000000 ffff8801d1b6a600 0000000100000003 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8801d1b6b400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8801d1b6b480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff8801d1b6b500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff8801d1b6b580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8801d1b6b600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > This issue should have been fixed by the following one-line change: diff --git a/drivers/block/brd.c b/drivers/block/brd.c index df8103dd40ac..a5ecff2071ce 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -515,6 +515,8 @@ static int __init brd_init(void) out_free: list_for_each_entry_safe(brd, next, &brd_devices, brd_list) { list_del(&brd->brd_list); + /* don't let put_disk() drop the queue's ref */ + brd->brd_disk->queue = NULL; brd_free(brd); } unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); -- Ming
