Re: [syzbot] [mm?] INFO: rcu detected stall in sys_umount (3)

Re: [syzbot] [mm?] INFO: rcu detected stall in sys_umount (3)

[syzbot]

syzbot has bisected this issue to:

commit d15121be7485655129101f3960ae6add40204463
Author: Paolo Abeni <pabeni@redhat.com>
Date:   Mon May 8 06:17:44 2023 +0000

    Revert "softirq: Let ksoftirqd do its job"

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1066f9f8580000
start commit:   feffde684ac2 Merge tag 'for-6.13-rc1-tag' of git://git.ker..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1266f9f8580000
console output: https://syzkaller.appspot.com/x/log.txt?x=1466f9f8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=50c7a61469ce77e7
dashboard link: https://syzkaller.appspot.com/bug?extid=1ec0f904ba50d06110b1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13c060f8580000

Reported-by: syzbot+1ec0f904ba50d06110b1@syzkaller.appspotmail.com
Fixes: d15121be7485 ("Revert "softirq: Let ksoftirqd do its job"")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [syzbot] [mm?] INFO: rcu detected stall in sys_umount (3)

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=1321eba2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5ac3d8b8abfcb
dashboard link: https://syzkaller.appspot.com/bug?extid=1ec0f904ba50d06110b1
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cba442580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10a1eba2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/18a2e4bd0c4a/disk-8f5ae30d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b5395881b25/vmlinux-8f5ae30d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e875f4e3b7ff/Image-8f5ae30d.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/43186d9e448c/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=174ba442580000)

The issue was bisected to:

commit d15121be7485655129101f3960ae6add40204463
Author: Paolo Abeni <pabeni@redhat.com>
Date:   Mon May 8 06:17:44 2023 +0000

    Revert "softirq: Let ksoftirqd do its job"

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1066f9f8580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1266f9f8580000
console output: https://syzkaller.appspot.com/x/log.txt?x=1466f9f8580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1ec0f904ba50d06110b1@syzkaller.appspotmail.com
Fixes: d15121be7485 ("Revert "softirq: Let ksoftirqd do its job"")

watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [syz-executor:6662]
Modules linked in:
irq event stamp: 355416
hardirqs last  enabled at (355415): [<ffff80008b00487c>] __exit_to_kernel_mode arch/arm64/kernel/entry-common.c:86 [inline]
hardirqs last  enabled at (355415): [<ffff80008b00487c>] exit_to_kernel_mode+0xc0/0xf0 arch/arm64/kernel/entry-common.c:96
hardirqs last disabled at (355416): [<ffff80008b001cbc>] __el1_irq arch/arm64/kernel/entry-common.c:650 [inline]
hardirqs last disabled at (355416): [<ffff80008b001cbc>] el1_interrupt+0x24/0x54 arch/arm64/kernel/entry-common.c:668
softirqs last  enabled at (355404): [<ffff8000803d88a0>] softirq_handle_end kernel/softirq.c:425 [inline]
softirqs last  enabled at (355404): [<ffff8000803d88a0>] handle_softirqs+0xaf8/0xc88 kernel/softirq.c:607
softirqs last disabled at (355387): [<ffff800080022028>] __do_softirq+0x14/0x20 kernel/softirq.c:613
CPU: 1 UID: 0 PID: 6662 Comm: syz-executor Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : propagation_source fs/pnode.c:77 [inline]
pc : change_mnt_propagation+0xec/0x77c fs/pnode.c:114
lr : propagation_source fs/pnode.c:78 [inline]
lr : change_mnt_propagation+0x120/0x77c fs/pnode.c:114
sp : ffff8000a4a07a90
x29: ffff8000a4a07ac0 x28: dfff800000000000 x27: ffff0000efa88b60
x26: ffff0000efa88bb0 x25: 1fffe0001df51176 x24: ffff0000efa88b18
x23: ffff0000f331b238 x22: ffff0000efa88a80 x21: ffff0000efa88a80
x20: 0000000000040000 x19: ffff0000f3339500 x18: 1fffe000337a0688
x17: ffff80008f7be000 x16: ffff80008af6de48 x15: 0000000000000002
x14: 1fffe0001df5116f x13: 0000000000000000 x12: 0000000000000000
x11: ffff60001df51171 x10: 0000000000ff0100 x9 : 0000000000000000
x8 : ffff0000f33395b8 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000008 x3 : 0000000000000000
x2 : 0000000000000008 x1 : 0000000000000001 x0 : 0000000000000000
Call trace:
 next_peer fs/pnode.c:19 [inline] (P)
 propagation_source fs/pnode.c:77 [inline] (P)
 change_mnt_propagation+0xec/0x77c fs/pnode.c:114 (P)
 umount_tree+0x7e4/0xbbc fs/namespace.c:1872
 do_umount fs/namespace.c:-1 [inline]
 path_umount+0x90c/0x980 fs/namespace.c:2095
 ksys_umount fs/namespace.c:2118 [inline]
 __do_sys_umount fs/namespace.c:2123 [inline]
 __se_sys_umount fs/namespace.c:2121 [inline]
 __arm64_sys_umount+0x128/0x174 fs/namespace.c:2121
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6746 Comm: syz-executor Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : cpu_relax arch/arm64/include/asm/vdso/processor.h:12 [inline]
pc : path_init+0xdc0/0xe98 fs/namei.c:2537
lr : path_init+0xdc0/0xe98 fs/namei.c:2537
sp : ffff8000a4247680
x29: ffff8000a42476e0 x28: dfff800000000000 x27: 1fffe00019832884
x26: ffff0000cc194420 x25: 0000000000000101 x24: 1ffff00014848f43
x23: ffff80008f745840 x22: ffff8000a4247a1c x21: 0000000000000100
x20: ffff8000a42479e0 x19: 000000000004a017 x18: 0000000000000000
x17: 0000000000000000 x16: ffff80008b007230 x15: 0000000000000001
x14: 1ffff00011ee8b08 x13: 0000000000000000 x12: 0000000000000000
x11: ffff700011ee8b09 x10: 0000000000ff0100 x9 : 0000000000000000
x8 : ffff0000da1e0000 x7 : ffff800080daa4c4 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff800080da8a84
x2 : 0000000000000000 x1 : 0000000000000004 x0 : 0000000000000001
Call trace:
 path_init+0xdc0/0xe98 fs/namei.c:2537 (P)
 path_openat+0x13c/0x2c40 fs/namei.c:4041
 do_filp_open+0x18c/0x36c fs/namei.c:4073
 do_open_execat+0x124/0x4d8 fs/exec.c:783
 alloc_bprm+0x3c/0x548 fs/exec.c:1410
 do_execveat_common+0x168/0x834 fs/exec.c:1811
 do_execve fs/exec.c:1934 [inline]
 __do_sys_execve fs/exec.c:2010 [inline]
 __se_sys_execve fs/exec.c:2005 [inline]
 __arm64_sys_execve+0x9c/0xb4 fs/exec.c:2005
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596


---
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.

Re: [syzbot] [mm?] INFO: rcu detected stall in sys_umount (3)

[Al Viro]

On Mon, Aug 18, 2025 at 02:42:28AM -0700, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=1321eba2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5ac3d8b8abfcb
> dashboard link: https://syzkaller.appspot.com/bug?extid=1ec0f904ba50d06110b1
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cba442580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10a1eba2580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/18a2e4bd0c4a/disk-8f5ae30d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/3b5395881b25/vmlinux-8f5ae30d.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e875f4e3b7ff/Image-8f5ae30d.gz.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/43186d9e448c/mount_0.gz
>   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=174ba442580000)
> 
> The issue was bisected to:
> 
> commit d15121be7485655129101f3960ae6add40204463
> Author: Paolo Abeni <pabeni@redhat.com>
> Date:   Mon May 8 06:17:44 2023 +0000
> 
>     Revert "softirq: Let ksoftirqd do its job"

Would be interesting to see how it behaves on 

git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #fixes (cda250b0fc83)

Re: [syzbot] [mm?] INFO: rcu detected stall in sys_umount (3)

[Hillf Danton]

On Mon, 18 Aug 2025 19:26:16 +0100 Al Viro wrote:
> On Mon, Aug 18, 2025 at 02:42:28AM -0700, syzbot wrote:
> > syzbot has found a reproducer for the following issue on:
> > 
> > HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
> > git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1321eba2580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5ac3d8b8abfcb
> > dashboard link: https://syzkaller.appspot.com/bug?extid=1ec0f904ba50d06110b1
> > compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> > userspace arch: arm64
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cba442580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10a1eba2580000
> > 
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/18a2e4bd0c4a/disk-8f5ae30d.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/3b5395881b25/vmlinux-8f5ae30d.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/e875f4e3b7ff/Image-8f5ae30d.gz.xz
> > mounted in repro: https://storage.googleapis.com/syzbot-assets/43186d9e448c/mount_0.gz
> >   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=174ba442580000)
> > 
> > The issue was bisected to:
> > 
> > commit d15121be7485655129101f3960ae6add40204463
> > Author: Paolo Abeni <pabeni@redhat.com>
> > Date:   Mon May 8 06:17:44 2023 +0000
> > 
> >     Revert "softirq: Let ksoftirqd do its job"
> 
> Would be interesting to see how it behaves on 

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git  fixes

Re: [syzbot] [mm?] INFO: rcu detected stall in sys_umount (3)

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+1ec0f904ba50d06110b1@syzkaller.appspotmail.com
Tested-by: syzbot+1ec0f904ba50d06110b1@syzkaller.appspotmail.com

Tested on:

commit:         cda250b0 change_mnt_propagation(): calculate propagati..
git tree:       vfs-fixes
console output: https://syzkaller.appspot.com/x/log.txt?x=13eb7ba2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2e92a122a0cf6f2a
dashboard link: https://syzkaller.appspot.com/bug?extid=1ec0f904ba50d06110b1
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.