On Wed, Apr 03, 2024 at 11:47:17AM +0200, Jan Kara wrote: > On Tue 02-04-24 07:38:25, syzbot wrote: > > syzbot has found a reproducer for the following issue on: > > > > HEAD commit: c0b832517f62 Add linux-next specific files for 20240402 > > git tree: linux-next > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=14af7dd9180000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=afcaf46d374cec8c > > dashboard link: https://syzkaller.appspot.com/bug?extid=7b219b86935220db6dd8 > > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1729f003180000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fa4341180000 > > > > Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/0d36ec76edc7/disk-c0b83251.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/6f9bb4e37dd0/vmlinux-c0b83251.xz > > kernel image: https://storage.googleapis.com/syzbot-assets/2349287b14b7/bzImage-c0b83251.xz > > mounted in repro: https://storage.googleapis.com/syzbot-assets/9760c52a227c/mount_0.gz > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+7b219b86935220db6dd8@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > BUG: KASAN: slab-out-of-bounds in __lock_acquire+0x78/0x1fd0 kernel/locking/lockdep.c:5005 > > Read of size 8 at addr ffff888020485fa8 by task kworker/u8:2/35 > > Looks like the writeback cleanups are causing some use-after-free issues. > The code KASAN is complaining about is: > > /* > * Nothing written. Wait for some inode to > * become available for writeback. Otherwise > * we'll just busyloop. > */ > trace_writeback_wait(wb, work); > inode = wb_inode(wb->b_more_io.prev); > >>>>> spin_lock(&inode->i_lock); <<<<<< > spin_unlock(&wb->list_lock); > /* This function drops i_lock... */ > inode_sleep_on_writeback(inode); > > in wb_writeback(). Now looking at the changes indeed the commit > 167d6693deb ("fs/writeback: bail out if there is no more inodes for IO and > queued once") is buggy because it will result in trying to fetch 'inode' > from empty b_more_io list and thus we'll corrupt memory. I think instead of > modifying the condition: > > if (list_empty(&wb->b_more_io)) { > > we should do: > > - if (progress) { > + if (progress || !queued) { > spin_unlock(&wb->list_lock); > continue; > } > > Kemeng? Fwiw, I observed this on xfstest too the last few days and tracked it down to this series. Here's the splat I got in case it helps: Apr 05 00:33:06 localhost kernel: ================================================================== Apr 05 00:33:06 localhost kernel: BUG: KASAN: slab-out-of-bounds in __lock_acquire.isra.0+0x1075/0x1280 Apr 05 00:33:06 localhost kernel: Read of size 8 at addr ffff88810ed40f48 by task kworker/u128:2/305560 Apr 05 00:33:06 localhost kernel: Apr 05 00:33:06 localhost kernel: CPU: 5 PID: 305560 Comm: kworker/u128:2 Not tainted 99.9.0-rc2-gdebeafad51e2 #262 Apr 05 00:33:06 localhost kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009)/Incus, BIOS unknown 2/2/2022 Apr 05 00:33:06 localhost kernel: Workqueue: writeback wb_workfn (flush-259:0) Apr 05 00:33:06 localhost kernel: Call Trace: Apr 05 00:33:06 localhost kernel: <TASK> Apr 05 00:33:06 localhost kernel: dump_stack_lvl+0x5a/0x90 Apr 05 00:33:06 localhost kernel: print_report+0xce/0x650 Apr 05 00:33:06 localhost kernel: ? __virt_addr_valid+0x217/0x320 Apr 05 00:33:06 localhost kernel: kasan_report+0xd7/0x110 Apr 05 00:33:06 localhost kernel: ? __lock_acquire.isra.0+0x1075/0x1280 Apr 05 00:33:06 localhost kernel: ? __lock_acquire.isra.0+0x1075/0x1280 Apr 05 00:33:06 localhost kernel: __lock_acquire.isra.0+0x1075/0x1280 Apr 05 00:33:06 localhost kernel: lock_acquire+0x136/0x330 Apr 05 00:33:06 localhost kernel: ? wb_writeback+0x255/0x870 Apr 05 00:33:06 localhost kernel: _raw_spin_lock+0x33/0x40 Apr 05 00:33:06 localhost kernel: ? wb_writeback+0x255/0x870 Apr 05 00:33:06 localhost kernel: wb_writeback+0x255/0x870 Apr 05 00:33:06 localhost kernel: ? __pfx_wb_writeback+0x10/0x10 Apr 05 00:33:06 localhost kernel: ? __pfx_lock_release+0x10/0x10 Apr 05 00:33:06 localhost kernel: wb_workfn+0x221/0xc80 Apr 05 00:33:06 localhost kernel: ? __pfx_wb_workfn+0x10/0x10 Apr 05 00:33:06 localhost kernel: ? lock_acquire+0x136/0x330 Apr 05 00:33:06 localhost kernel: process_one_work+0x82d/0x1790 Apr 05 00:33:06 localhost kernel: ? __pfx_process_one_work+0x10/0x10 Apr 05 00:33:06 localhost kernel: ? assign_work+0x16c/0x240 Apr 05 00:33:06 localhost kernel: worker_thread+0x724/0x1300 Apr 05 00:33:06 localhost kernel: ? __kthread_parkme+0xba/0x1f0 Apr 05 00:33:06 localhost kernel: ? __pfx_worker_thread+0x10/0x10 Apr 05 00:33:06 localhost kernel: kthread+0x2ed/0x3d0 Apr 05 00:33:06 localhost kernel: ? __pfx_kthread+0x10/0x10 Apr 05 00:33:06 localhost kernel: ret_from_fork+0x31/0x70 Apr 05 00:33:06 localhost kernel: ? __pfx_kthread+0x10/0x10 Apr 05 00:33:06 localhost kernel: ret_from_fork_asm+0x1a/0x30 Apr 05 00:33:06 localhost kernel: </TASK> Apr 05 00:33:06 localhost kernel: Apr 05 00:33:06 localhost kernel: Allocated by task 1: Apr 05 00:33:06 localhost kernel: kasan_save_stack+0x33/0x60 Apr 05 00:33:06 localhost kernel: kasan_save_track+0x14/0x30 Apr 05 00:33:06 localhost kernel: __kasan_kmalloc+0xaa/0xb0 Apr 05 00:33:06 localhost kernel: psi_cgroup_alloc+0x57/0x2b0 Apr 05 00:33:06 localhost kernel: cgroup_mkdir+0x4f8/0xfb0 Apr 05 00:33:06 localhost kernel: kernfs_iop_mkdir+0x133/0x1c0 Apr 05 00:33:06 localhost kernel: vfs_mkdir+0x3b9/0x610 Apr 05 00:33:06 localhost kernel: do_mkdirat+0x27e/0x300 Apr 05 00:33:06 localhost kernel: __x64_sys_mkdir+0x65/0x80 Apr 05 00:33:06 localhost kernel: do_syscall_64+0x64/0x190 Apr 05 00:33:06 localhost kernel: entry_SYSCALL_64_after_hwframe+0x71/0x79 Apr 05 00:33:06 localhost kernel: Apr 05 00:33:06 localhost kernel: Last potentially related work creation: Apr 05 00:33:06 localhost kernel: kasan_save_stack+0x33/0x60 Apr 05 00:33:06 localhost kernel: __kasan_record_aux_stack+0xad/0xc0 Apr 05 00:33:06 localhost kernel: insert_work+0x32/0x1f0 Apr 05 00:33:06 localhost kernel: __queue_work+0x5cb/0xcb0 Apr 05 00:33:06 localhost kernel: call_timer_fn+0x16d/0x490 Apr 05 00:33:06 localhost kernel: __run_timers+0x488/0x980 Apr 05 00:33:06 localhost kernel: run_timer_base+0xfb/0x170 Apr 05 00:33:06 localhost kernel: run_timer_softirq+0x1a/0x30 Apr 05 00:33:06 localhost kernel: __do_softirq+0x26a/0x7d2 Apr 05 00:33:06 localhost kernel: Apr 05 00:33:06 localhost kernel: Second to last potentially related work creation: Apr 05 00:33:06 localhost kernel: kasan_save_stack+0x33/0x60 Apr 05 00:33:06 localhost kernel: __kasan_record_aux_stack+0xad/0xc0 Apr 05 00:33:06 localhost kernel: insert_work+0x32/0x1f0 Apr 05 00:33:06 localhost kernel: __queue_work+0x5cb/0xcb0 Apr 05 00:33:06 localhost kernel: call_timer_fn+0x16d/0x490 Apr 05 00:33:06 localhost kernel: __run_timers+0x488/0x980 Apr 05 00:33:06 localhost kernel: timer_expire_remote+0xe6/0x150 Apr 05 00:33:06 localhost kernel: tmigr_handle_remote+0x6e2/0xe00 Apr 05 00:33:06 localhost kernel: __do_softirq+0x26a/0x7d2 Apr 05 00:33:06 localhost kernel: Apr 05 00:33:06 localhost kernel: The buggy address belongs to the object at ffff88810ed40000 which belongs to the cache kmalloc-2k of size 2048 Apr 05 00:33:06 localhost kernel: The buggy address is located 2792 bytes to the right of allocated 1120-byte region [ffff88810ed40000, ffff88810ed40460) Apr 05 00:33:06 localhost kernel: Apr 05 00:33:06 localhost kernel: The buggy address belongs to the physical page: Apr 05 00:33:06 localhost kernel: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88810ed45000 pfn:0x10ed40 Apr 05 00:33:06 localhost kernel: head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0 Apr 05 00:33:06 localhost kernel: flags: 0x200000000000840(slab|head|node=0|zone=2) Apr 05 00:33:06 localhost kernel: page_type: 0xffffffff() Apr 05 00:33:06 localhost kernel: raw: 0200000000000840 ffff888100042f00 ffffea00040f1a00 dead000000000002 Apr 05 00:33:06 localhost kernel: raw: ffff88810ed45000 0000000080080006 00000001ffffffff 0000000000000000 Apr 05 00:33:06 localhost kernel: head: 0200000000000840 ffff888100042f00 ffffea00040f1a00 dead000000000002 Apr 05 00:33:06 localhost kernel: head: ffff88810ed45000 0000000080080006 00000001ffffffff 0000000000000000 Apr 05 00:33:06 localhost kernel: head: 0200000000000003 ffffea00043b5001 dead000000000122 00000000ffffffff Apr 05 00:33:06 localhost kernel: head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000 Apr 05 00:33:06 localhost kernel: page dumped because: kasan: bad access detected Apr 05 00:33:06 localhost kernel: Apr 05 00:33:06 localhost kernel: Memory state around the buggy address: Apr 05 00:33:06 localhost kernel: ffff88810ed40e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc Apr 05 00:33:06 localhost kernel: ffff88810ed40e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc Apr 05 00:33:06 localhost kernel: >ffff88810ed40f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc Apr 05 00:33:06 localhost kernel: ^ Apr 05 00:33:06 localhost kernel: ffff88810ed40f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc Apr 05 00:33:06 localhost kernel: ffff88810ed41000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Apr 05 00:33:06 localhost kernel: ================================================================== Apr 05 00:33:06 localhost kernel: Disabling lock debugging due to kernel taint Apr 05 00:33:06 localhost kernel: INFO: trying to register non-static key. Apr 05 00:33:06 localhost kernel: The code is fine but needs lockdep annotation, or maybe Apr 05 00:33:06 localhost kernel: you didn't initialize this object before use? Apr 05 00:33:06 localhost kernel: turning off the locking correctness validator. Apr 05 00:33:06 localhost kernel: CPU: 5 PID: 305560 Comm: kworker/u128:2 Tainted: G B 99.9.0-rc2-gdebeafad51e2 #262 Apr 05 00:33:06 localhost kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009)/Incus, BIOS unknown 2/2/2022 Apr 05 00:33:06 localhost kernel: Workqueue: writeback wb_workfn (flush-259:0) Apr 05 00:33:06 localhost kernel: Call Trace: Apr 05 00:33:06 localhost kernel: <TASK> Apr 05 00:33:06 localhost kernel: dump_stack_lvl+0x5a/0x90 Apr 05 00:33:06 localhost kernel: register_lock_class+0x11dd/0x1860 Apr 05 00:33:06 localhost kernel: ? add_taint+0x2a/0x90 Apr 05 00:33:06 localhost kernel: ? end_report+0x85/0x180 Apr 05 00:33:06 localhost kernel: ? __pfx_register_lock_class+0x10/0x10 Apr 05 00:33:06 localhost kernel: __lock_acquire.isra.0+0x7f/0x1280 Apr 05 00:33:06 localhost kernel: lock_acquire+0x136/0x330 Apr 05 00:33:06 localhost kernel: ? wb_writeback+0x255/0x870 Apr 05 00:33:06 localhost kernel: _raw_spin_lock+0x33/0x40 Apr 05 00:33:06 localhost kernel: ? wb_writeback+0x255/0x870 Apr 05 00:33:06 localhost kernel: wb_writeback+0x255/0x870 Apr 05 00:33:06 localhost kernel: ? __pfx_wb_writeback+0x10/0x10 Apr 05 00:33:06 localhost kernel: ? __pfx_lock_release+0x10/0x10 Apr 05 00:33:06 localhost kernel: wb_workfn+0x221/0xc80 Apr 05 00:33:06 localhost kernel: ? __pfx_wb_workfn+0x10/0x10 Apr 05 00:33:06 localhost kernel: ? lock_acquire+0x136/0x330 Apr 05 00:33:06 localhost kernel: process_one_work+0x82d/0x1790 Apr 05 00:33:06 localhost kernel: ? __pfx_process_one_work+0x10/0x10 Apr 05 00:33:06 localhost kernel: ? assign_work+0x16c/0x240 Apr 05 00:33:06 localhost kernel: worker_thread+0x724/0x1300 Apr 05 00:33:06 localhost kernel: ? __kthread_parkme+0xba/0x1f0 Apr 05 00:33:06 localhost kernel: ? __pfx_worker_thread+0x10/0x10 Apr 05 00:33:06 localhost kernel: kthread+0x2ed/0x3d0 Apr 05 00:33:06 localhost kernel: ? __pfx_kthread+0x10/0x10 Apr 05 00:33:06 localhost kernel: ret_from_fork+0x31/0x70 Apr 05 00:33:06 localhost kernel: ? __pfx_kthread+0x10/0x10 Apr 05 00:33:06 localhost kernel: ret_from_fork_asm+0x1a/0x30 Apr 05 00:33:06 localhost kernel: </TASK>
