* Re: [syzbot] [integrity?] [lsm?] possible deadlock in __configfs_open_file (2)
2026-10-13 22:22 ` [syzbot] [integrity?] [lsm?] possible deadlock in __configfs_open_file (2) syzbot
@ 2026-10-14 0:24 ` Mimi Zohar
0 siblings, 0 replies; 2+ messages in thread
From: Mimi Zohar @ 2026-10-14 0:24 UTC (permalink / raw)
To: syzbot, a.hindborg, leitao, linux-fsdevel, linux-integrity,
linux-kernel, linux-security-module, syzkaller-bugs
On Tue, 2026-10-13 at 15:22 -0700, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 24a19b953e2a Linux 7.3-rc7
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> console output: https://syzkaller.appspot.com/x/log.txt?x=165f3c35580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=129d675874dbf896
> dashboard link: https://syzkaller.appspot.com/bug?extid=c87014f645f2fd24312e
> compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10cf93d1580000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c87014f645f2fd24312e@syzkaller.appspotmail.com
>
Commits 8e22ce504f8a ("ima: don't measure/appraise files on configfs") and
ab84c314417e ("configfs: move CONFIGFS_MAGIC definition to magic.h") addressed
this or a similar issue for the builtin IMA policies. If you're using a custom
IMA policy, it needs a configfs dont_measure and/or dont_appraise rule.
Please provide the IMA policy.
Mimi
> ======================================================
> WARNING: possible circular locking dependency detected
> syzkaller #0 Not tainted
> ------------------------------------------------------
> syz-executor387/5997 is trying to acquire lock:
> ffff888035be1570 (&p->frag_sem){.+.+}-{4:4}, at: __configfs_open_file+0xe8/0x9c0 fs/configfs/file.c:304
>
> but task is already holding lock:
> ffffffff91d84848 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #3 (cb_lock){++++}-{4:4}:
> lock_acquire kernel/locking/lockdep.c:5942 [inline]
> lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
> down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
> genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
> netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline]
> netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1364
> netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1919
> sock_sendmsg_nosec net/socket.c:800 [inline]
> __sock_sendmsg net/socket.c:815 [inline]
> sock_sendmsg+0x394/0x410 net/socket.c:838
> splice_to_socket+0xb3c/0x11a0 fs/splice.c:884
> do_splice_from fs/splice.c:936 [inline]
> do_splice+0x109c/0x1fa0 fs/splice.c:1349
> __do_splice+0x33b/0x370 fs/splice.c:1431
> __do_sys_splice fs/splice.c:1634 [inline]
> __se_sys_splice fs/splice.c:1616 [inline]
> __x64_sys_splice+0x187/0x250 fs/splice.c:1616
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #2 (&pipe->mutex){+.+.}-{4:4}:
> lock_acquire kernel/locking/lockdep.c:5942 [inline]
> lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
> __mutex_lock_common kernel/locking/mutex.c:646 [inline]
> __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
> fifo_open+0x139/0xb40 fs/pipe.c:1235
> do_dentry_open+0x6ab/0x14d0 fs/open.c:996
> vfs_open+0x82/0x3f0 fs/open.c:1101
> do_open fs/namei.c:4866 [inline]
> path_openat+0x19fa/0x2440 fs/namei.c:5029
> do_file_open+0x20e/0x430 fs/namei.c:5058
> file_open_name+0x1c3/0x3e0 fs/open.c:1375
> filp_open+0x2e/0x50 fs/open.c:1392
> fsg_lun_open+0x6b/0x7b0 drivers/usb/gadget/function/storage_common.c:194
> fsg_store_file+0x1e7/0x450 drivers/usb/gadget/function/storage_common.c:455
> flush_write_buffer fs/configfs/file.c:207 [inline]
> configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229
> new_sync_write fs/read_write.c:595 [inline]
> vfs_write+0x6af/0x1050 fs/read_write.c:687
> ksys_write+0x12a/0x250 fs/read_write.c:739
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #1 (&common->filesem){+.+.}-{4:4}:
> lock_acquire kernel/locking/lockdep.c:5942 [inline]
> lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
> down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631
> fsg_store_file+0x264/0x450 drivers/usb/gadget/function/storage_common.c:452
> flush_write_buffer fs/configfs/file.c:207 [inline]
> configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229
> new_sync_write fs/read_write.c:595 [inline]
> vfs_write+0x6af/0x1050 fs/read_write.c:687
> ksys_write+0x12a/0x250 fs/read_write.c:739
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #0 (&p->frag_sem){.+.+}-{4:4}:
> check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
> check_prevs_add kernel/locking/lockdep.c:3328 [inline]
> validate_chain kernel/locking/lockdep.c:3952 [inline]
> __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
> lock_acquire kernel/locking/lockdep.c:5942 [inline]
> lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
> down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
> __configfs_open_file+0xe8/0x9c0 fs/configfs/file.c:304
> do_dentry_open+0x6ab/0x14d0 fs/open.c:996
> vfs_open+0x82/0x3f0 fs/open.c:1101
> do_open fs/namei.c:4866 [inline]
> path_openat+0x19fa/0x2440 fs/namei.c:5029
> do_file_open+0x20e/0x430 fs/namei.c:5058
> file_open_name+0x1c3/0x3e0 fs/open.c:1375
> filp_open+0x2e/0x50 fs/open.c:1392
> kernel_read_file_from_path_initns+0xec/0x240 fs/kernel_read_file.c:159
> fw_get_filesystem_firmware drivers/base/firmware_loader/main.c:549 [inline]
> _request_firmware+0x733/0x13c0 drivers/base/firmware_loader/main.c:873
> request_firmware+0x35/0x50 drivers/base/firmware_loader/main.c:948
> reg_reload_regdb+0x85/0x460 net/wireless/reg.c:1067
> genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114
> genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
> genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209
> netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2575
> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
> netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline]
> netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1364
> netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1919
> sock_sendmsg_nosec net/socket.c:800 [inline]
> __sock_sendmsg net/socket.c:815 [inline]
> sock_sendmsg+0x394/0x410 net/socket.c:838
> splice_to_socket+0xb3c/0x11a0 fs/splice.c:884
> do_splice_from fs/splice.c:936 [inline]
> do_splice+0x109c/0x1fa0 fs/splice.c:1349
> __do_splice+0x33b/0x370 fs/splice.c:1431
> __do_sys_splice fs/splice.c:1634 [inline]
> __se_sys_splice fs/splice.c:1616 [inline]
> __x64_sys_splice+0x187/0x250 fs/splice.c:1616
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> other info that might help us debug this:
>
> Chain exists of:
> &p->frag_sem --> &pipe->mutex --> cb_lock
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> rlock(cb_lock);
> lock(&pipe->mutex);
> lock(cb_lock);
> rlock(&p->frag_sem);
>
> *** DEADLOCK ***
>
> locks held by syz-executor387/5997: 2, last CPU#0:
> #0: ffff888035fc7860 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline]
> #0: ffff888035fc7860 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x69/0x80 fs/pipe.c:88
> #1: ffffffff91d84848 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 5997 Comm: syz-executor387 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:94 [inline]
> dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
> print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
> check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
> check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
> check_prevs_add kernel/locking/lockdep.c:3328 [inline]
> validate_chain kernel/locking/lockdep.c:3952 [inline]
> __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
> lock_acquire kernel/locking/lockdep.c:5942 [inline]
> lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
> down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
> __configfs_open_file+0xe8/0x9c0 fs/configfs/file.c:304
> do_dentry_open+0x6ab/0x14d0 fs/open.c:996
> vfs_open+0x82/0x3f0 fs/open.c:1101
> do_open fs/namei.c:4866 [inline]
> path_openat+0x19fa/0x2440 fs/namei.c:5029
> do_file_open+0x20e/0x430 fs/namei.c:5058
> file_open_name+0x1c3/0x3e0 fs/open.c:1375
> filp_open+0x2e/0x50 fs/open.c:1392
> kernel_read_file_from_path_initns+0xec/0x240 fs/kernel_read_file.c:159
> fw_get_filesystem_firmware drivers/base/firmware_loader/main.c:549 [inline]
> _request_firmware+0x733/0x13c0 drivers/base/firmware_loader/main.c:873
> request_firmware+0x35/0x50 drivers/base/firmware_loader/main.c:948
> reg_reload_regdb+0x85/0x460 net/wireless/reg.c:1067
> genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114
> genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
> genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209
> netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2575
> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
> netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline]
> netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1364
> netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1919
> sock_sendmsg_nosec net/socket.c:800 [inline]
> __sock_sendmsg net/socket.c:815 [inline]
> sock_sendmsg+0x394/0x410 net/socket.c:838
> splice_to_socket+0xb3c/0x11a0 fs/splice.c:884
> do_splice_from fs/splice.c:936 [inline]
> do_splice+0x109c/0x1fa0 fs/splice.c:1349
> __do_splice+0x33b/0x370 fs/splice.c:1431
> __do_sys_splice fs/splice.c:1634 [inline]
> __se_sys_splice fs/splice.c:1616 [inline]
> __x64_sys_splice+0x187/0x250 fs/splice.c:1616
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f7180644b5e
> Code: 08 0f 85 f5 e2 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08
> RSP: 002b:00007f717cde6f18 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
> RAX: ffffffffffffffda RBX: 00007f717cde76c0 RCX: 00007f7180644b5e
> RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000011
> RBP: 00007f717cde6fe0 R08: 0000000000000014 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000012
> R13: 00007f717cde6f80 R14: 000000000000017e R15: 0000000000000010
> </TASK>
> faux_driver regulatory: loading /lib/firmware/regulatory.db failed with error -26
> faux_driver regulatory: Direct firmware load for regulatory.db failed with error -26
> faux_driver regulatory: Falling back to sysfs fallback for: regulatory.db
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
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