syzbot


possible deadlock in ovl_copy_up_flags

Status: upstream: reported C repro on 2024/05/23 10:09
Subsystems: overlayfs
[Documentation on labels]
Reported-by: syzbot+85e58cdf5b3136471d4b@syzkaller.appspotmail.com
Fix commit: ovl: fix copy-up in tmpfile
Patched on: [ci-upstream-linux-next-kasan-gce-root], missing on: [ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-net-next-test-gce ci2-upstream-usb]
First crash: 26d, last: 1d00h
Cause bisection: introduced by (bisect log) :
commit 9a87907de3597a339cc129229d1a20bc7365ea5f
Author: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu May 2 18:35:57 2024 +0000

  ovl: implement tmpfile

Crash: possible deadlock in ovl_copy_up_flags (log)
Repro: C syz .config
  
Duplicate bugs (1)
duplicates (1):
Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
possible deadlock in ovl_copy_up_one overlayfs C 4 4d13h 13h37m 0/27 closed as dup on 2024/06/14 07:11
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [btrfs?] [overlayfs?] possible deadlock in ovl_copy_up_flags 2 (4) 2024/05/27 21:36
Last patch testing requests (1)
Created Duration User Patch Repo Result
2024/05/27 13:51 30m miklos@szeredi.hu git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs.git f74ee925761ead1a07a5e42e1cb1f2d59ab75b8c OK log

Sample crash report:
============================================
WARNING: possible recursive locking detected
6.10.0-rc2-syzkaller-00366-g771ed66105de #0 Not tainted
--------------------------------------------
syz-executor122/5081 is trying to acquire lock:
ffff88802f7a2420 (sb_writers#4){.+.+}-{0:0}, at: ovl_do_copy_up fs/overlayfs/copy_up.c:967 [inline]
ffff88802f7a2420 (sb_writers#4){.+.+}-{0:0}, at: ovl_copy_up_one fs/overlayfs/copy_up.c:1168 [inline]
ffff88802f7a2420 (sb_writers#4){.+.+}-{0:0}, at: ovl_copy_up_flags+0x1110/0x4470 fs/overlayfs/copy_up.c:1223

but task is already holding lock:
ffff88802f7a2420 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:409

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(sb_writers#4);
  lock(sb_writers#4);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by syz-executor122/5081:
 #0: ffff888022d3a420 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:409
 #1: ffff88802f7a2420 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:409
 #2: ffff88807d238528 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:657 [inline]
 #2: ffff88807d238528 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_copy_up_start+0x53/0x310 fs/overlayfs/util.c:719

stack backtrace:
CPU: 1 PID: 5081 Comm: syz-executor122 Not tainted 6.10.0-rc2-syzkaller-00366-g771ed66105de #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 check_deadlock kernel/locking/lockdep.c:3062 [inline]
 validate_chain+0x15d3/0x5900 kernel/locking/lockdep.c:3856
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1655 [inline]
 sb_start_write include/linux/fs.h:1791 [inline]
 ovl_start_write+0x11d/0x290 fs/overlayfs/util.c:31
 ovl_do_copy_up fs/overlayfs/copy_up.c:967 [inline]
 ovl_copy_up_one fs/overlayfs/copy_up.c:1168 [inline]
 ovl_copy_up_flags+0x1110/0x4470 fs/overlayfs/copy_up.c:1223
 ovl_create_tmpfile fs/overlayfs/dir.c:1317 [inline]
 ovl_tmpfile+0x262/0x6d0 fs/overlayfs/dir.c:1373
 vfs_tmpfile+0x396/0x510 fs/namei.c:3701
 do_tmpfile+0x156/0x340 fs/namei.c:3764
 path_openat+0x2ab8/0x3280 fs/namei.c:3798
 do_filp_open+0x235/0x490 fs/namei.c:3834
 do_sys_openat2+0x13e/0x1d0 fs/open.c:1405
 do_sys_open fs/open.c:1420 [inline]
 __do_sys_open fs/open.c:1428 [inline]
 __se_sys_open fs/open.c:1424 [inline]
 __x64_sys_open+0x225/0x270 fs/open.c:1424
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4cddd5ef49
Code: 48 83 c4 28 c3 e8 67 17 00 00 0f 1f 80 00 00 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc02708338 EFLAGS: 00000246 ORIG_RAX: 000000000

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/06/09 23:43 upstream 771ed66105de 82c05ab8 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in ovl_copy_up_flags
2024/06/08 07:58 upstream 96e09b8f8166 82c05ab8 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in ovl_copy_up_flags
2024/05/19 11:11 linux-next c75962170e49 c0f1611a .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root possible deadlock in ovl_copy_up_flags
2024/06/13 12:05 upstream 2ccbdf43d5e7 2aa5052f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in ovl_copy_up_flags
2024/06/09 23:02 upstream 771ed66105de 82c05ab8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in ovl_copy_up_flags
2024/06/09 22:56 upstream 771ed66105de 82c05ab8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root possible deadlock in ovl_copy_up_flags
2024/05/19 10:03 linux-next c75962170e49 c0f1611a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in ovl_copy_up_flags
* Struck through repros no longer work on HEAD.