On 22.09.2018 22:30, syzbot wrote: > syzbot has found a reproducer for the following crash on: > > HEAD commit: 10dc890d4228 Merge tag 'pinctrl-v4.19-3' of git://git.kern.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1631cfbe400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5fa12be50bca08d8 > dashboard link: https://syzkaller.appspot.com/bug?extid=4e975615ca01f2277bdd > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15ffb766400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+4e975615ca01f2277bdd@xxxxxxxxxxxxxxxxxxxxxxxxx > > 8021q: adding VLAN 0 to HW filter on device team0 > 8021q: adding VLAN 0 to HW filter on device team0 > 8021q: adding VLAN 0 to HW filter on device team0 > 8021q: adding VLAN 0 to HW filter on device team0 > ================================================================== > BUG: KASAN: use-after-free in constant_test_bit arch/x86/include/asm/bitops.h:328 [inline] > BUG: KASAN: use-after-free in fuse_dev_do_read.isra.27+0x1659/0x1920 fs/fuse/dev.c:1318 > Read of size 8 at addr ffff8801d8702630 by task syz-executor1/7794 > > CPU: 0 PID: 7794 Comm: syz-executor1 Not tainted 4.19.0-rc4+ #26 > 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+0x1c4/0x2b4 lib/dump_stack.c:113 > print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256 > kasan_report_error mm/kasan/report.c:354 [inline] > kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412 > __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 > constant_test_bit arch/x86/include/asm/bitops.h:328 [inline] > fuse_dev_do_read.isra.27+0x1659/0x1920 fs/fuse/dev.c:1318 > fuse_dev_read+0x1a9/0x250 fs/fuse/dev.c:1360 > call_read_iter include/linux/fs.h:1802 [inline] > new_sync_read fs/read_write.c:406 [inline] > __vfs_read+0x6ac/0x9b0 fs/read_write.c:418 > vfs_read+0x17f/0x3c0 fs/read_write.c:452 > ksys_read+0x101/0x260 fs/read_write.c:578 > __do_sys_read fs/read_write.c:588 [inline] > __se_sys_read fs/read_write.c:586 [inline] > __x64_sys_read+0x73/0xb0 fs/read_write.c:586 > do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x457679 > Code: 1d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f6a5aeedc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > RAX: ffffffffffffffda RBX: 00007f6a5aeee6d4 RCX: 0000000000457679 > RDX: 0000000000001000 RSI: 0000000020001000 RDI: 0000000000000003 > RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff > R13: 00000000004d4ad0 R14: 00000000004c31e5 R15: 0000000000000000 > > Allocated by task 7801: > 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 > kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490 > kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554 > __fuse_request_alloc+0x27/0xf0 fs/fuse/dev.c:58 > fuse_request_alloc+0x18/0x20 fs/fuse/dev.c:89 > fuse_fill_super+0x12bf/0x1ea0 fs/fuse/inode.c:1157 > mount_nodev+0x6b/0x110 fs/super.c:1204 > fuse_mount+0x2c/0x40 fs/fuse/inode.c:1213 > mount_fs+0xae/0x31d fs/super.c:1261 > vfs_kern_mount.part.35+0xdc/0x4f0 fs/namespace.c:961 > vfs_kern_mount fs/namespace.c:951 [inline] > do_new_mount fs/namespace.c:2457 [inline] > do_mount+0x581/0x31f0 fs/namespace.c:2787 > ksys_mount+0x12d/0x140 fs/namespace.c:3003 > __do_sys_mount fs/namespace.c:3017 [inline] > __se_sys_mount fs/namespace.c:3014 [inline] > __x64_sys_mount+0xbe/0x150 fs/namespace.c:3014 > do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Freed by task 7801: > 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] > kmem_cache_free+0x83/0x290 mm/slab.c:3756 > fuse_request_free+0x8b/0xa0 fs/fuse/dev.c:104 > fuse_put_request+0x2a6/0x350 fs/fuse/dev.c:304 > request_end+0xba/0xaa0 fs/fuse/dev.c:414 > fuse_dev_do_write+0x192e/0x36e0 fs/fuse/dev.c:1915 > fuse_dev_write+0x19a/0x240 fs/fuse/dev.c:1939 > call_write_iter include/linux/fs.h:1808 [inline] > new_sync_write fs/read_write.c:474 [inline] > __vfs_write+0x6b8/0x9f0 fs/read_write.c:487 > vfs_write+0x1fc/0x560 fs/read_write.c:549 > ksys_write+0x101/0x260 fs/read_write.c:598 > __do_sys_write fs/read_write.c:610 [inline] > __se_sys_write fs/read_write.c:607 [inline] > __x64_sys_write+0x73/0xb0 fs/read_write.c:607 > do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > The buggy address belongs to the object at ffff8801d8702600 > which belongs to the cache fuse_request of size 448 > The buggy address is located 48 bytes inside of > 448-byte region [ffff8801d8702600, ffff8801d87027c0) > The buggy address belongs to the page: > page:ffffea000761c080 count:1 mapcount:0 mapping:ffff8801d4a0e240 index:0x0 > flags: 0x2fffc0000000100(slab) > raw: 02fffc0000000100 ffffea0006ec0e88 ffffea0006ee91c8 ffff8801d4a0e240 > raw: 0000000000000000 ffff8801d8702000 0000000100000008 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8801d8702500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8801d8702580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >> ffff8801d8702600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff8801d8702680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8801d8702700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== Fix from my previous message makes the use-after-free does not reproduce with the reproducer in my setup. I can prepare the patch, but before this some comments from Miklos would be welcome. Miklos, what you think about this? Kirill --- diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 11ea2c4a38ab..675caed3e655 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1311,12 +1311,14 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, goto out_end; } list_move_tail(&req->list, &fpq->processing); + __fuse_get_request(req); spin_unlock(&fpq->lock); set_bit(FR_SENT, &req->flags); /* matches barrier in request_wait_answer() */ smp_mb__after_atomic(); if (test_bit(FR_INTERRUPTED, &req->flags)) queue_interrupt(fiq, req); + fuse_put_request(fc, req); return reqsize;
