possible deadlock in userfaultfd_read (2)

From: syzbot
Date: Fri Mar 29 2019 - 06:34:09 EST

Next message: Oscar Salvador: "Re: [PATCH v3 1/2] mm/sparse: Clean up the obsolete code comment"
Previous message: Pavel Machek: "Re: kernfs: can read/write method grow buffer size?"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Hello,

syzbot found the following crash on:

HEAD commit: 1a9df9e2 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10ded663200000
kernel config: https://syzkaller.appspot.com/x/.config?x=8dcdce25ea72bedf
dashboard link: https://syzkaller.appspot.com/bug?extid=fab6de82892b6b9c6191
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fab6de82892b6b9c6191@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
5.1.0-rc2+ #40 Not tainted
-----------------------------------------------------
syz-executor.3/1446 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
000000004c6b904f (&ctx->fault_pending_wqh){+.+.}, at: spin_lock include/linux/spinlock.h:329 [inline]
000000004c6b904f (&ctx->fault_pending_wqh){+.+.}, at: userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
000000004c6b904f (&ctx->fault_pending_wqh){+.+.}, at: userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198

and this task is already holding:
00000000b0b711bd (&ctx->fd_wqh){....}, at: spin_lock_irq include/linux/spinlock.h:354 [inline]
00000000b0b711bd (&ctx->fd_wqh){....}, at: userfaultfd_ctx_read fs/userfaultfd.c:1036 [inline]
00000000b0b711bd (&ctx->fd_wqh){....}, at: userfaultfd_read+0x27a/0x1940 fs/userfaultfd.c:1198
which would create a new lock dependency:
(&ctx->fd_wqh){....} -> (&ctx->fault_pending_wqh){+.+.}

but this new dependency connects a SOFTIRQ-irq-safe lock:
(&(&ctx->ctx_lock)->rlock){..-.}

... which became SOFTIRQ-irq-safe at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
_raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0x2d/0x4a0 fs/aio.c:621
percpu_ref_put_many include/linux/percpu-refcount.h:285 [inline]
percpu_ref_put include/linux/percpu-refcount.h:301 [inline]
percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline]
percpu_ref_switch_to_atomic_rcu+0x3e7/0x520 lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:227 [inline]
rcu_do_batch kernel/rcu/tree.c:2475 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2788 [inline]
rcu_core+0x928/0x1390 kernel/rcu/tree.c:2769
__do_softirq+0x266/0x95a kernel/softirq.c:293
invoke_softirq kernel/softirq.c:374 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:414
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
__sanitizer_cov_trace_const_cmp1+0x5/0x20 kernel/kcov.c:175
tlb_flush_mmu_free+0x4e/0x120 mm/mmu_gather.c:74
zap_pte_range mm/memory.c:1158 [inline]
zap_pmd_range mm/memory.c:1193 [inline]
zap_pud_range mm/memory.c:1222 [inline]
zap_p4d_range mm/memory.c:1243 [inline]
unmap_page_range+0x180e/0x2330 mm/memory.c:1264
unmap_single_vma+0x19d/0x300 mm/memory.c:1309
unmap_vmas+0x115/0x250 mm/memory.c:1340
exit_mmap+0x2c2/0x530 mm/mmap.c:3138
__mmput kernel/fork.c:1046 [inline]
mmput+0x15f/0x4c0 kernel/fork.c:1067
exit_mm kernel/exit.c:546 [inline]
do_exit+0x816/0x2fa0 kernel/exit.c:863
do_group_exit+0x135/0x370 kernel/exit.c:980
get_signal+0x399/0x1d50 kernel/signal.c:2577
do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
prepare_exit_to_usermode+0x279/0x2e0 arch/x86/entry/common.c:197
retint_user+0x8/0x18

to a SOFTIRQ-irq-unsafe lock:
(&ctx->fault_pending_wqh){+.+.}

... which became SOFTIRQ-irq-unsafe at:
...
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
handle_userfault+0x58e/0x18c0 fs/userfaultfd.c:461
do_anonymous_page mm/memory.c:2941 [inline]
handle_pte_fault mm/memory.c:3807 [inline]
__handle_mm_fault+0x361d/0x3ec0 mm/memory.c:3933
handle_mm_fault+0x43f/0xb30 mm/memory.c:3970
do_user_addr_fault arch/x86/mm/fault.c:1475 [inline]
__do_page_fault+0x5ef/0xda0 arch/x86/mm/fault.c:1541
do_page_fault+0x71/0x581 arch/x86/mm/fault.c:1572
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143
__get_user_4+0x21/0x30 arch/x86/lib/getuser.S:76
sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3120
__sys_setsockopt+0x180/0x280 net/socket.c:2046
__do_sys_setsockopt net/socket.c:2057 [inline]
__se_sys_setsockopt net/socket.c:2054 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:2054
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
&(&ctx->ctx_lock)->rlock --> &ctx->fd_wqh --> &ctx->fault_pending_wqh

Possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ctx->fault_pending_wqh);
local_irq_disable();
lock(&(&ctx->ctx_lock)->rlock);
lock(&ctx->fd_wqh);
<Interrupt>
lock(&(&ctx->ctx_lock)->rlock);

*** DEADLOCK ***

1 lock held by syz-executor.3/1446:
#0: 00000000b0b711bd (&ctx->fd_wqh){....}, at: spin_lock_irq include/linux/spinlock.h:354 [inline]
#0: 00000000b0b711bd (&ctx->fd_wqh){....}, at: userfaultfd_ctx_read fs/userfaultfd.c:1036 [inline]
#0: 00000000b0b711bd (&ctx->fd_wqh){....}, at: userfaultfd_read+0x27a/0x1940 fs/userfaultfd.c:1198

the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
-> (&(&ctx->ctx_lock)->rlock){..-.} {
IN-SOFTIRQ-W at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
_raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0x2d/0x4a0 fs/aio.c:621
percpu_ref_put_many include/linux/percpu-refcount.h:285 [inline]
percpu_ref_put include/linux/percpu-refcount.h:301 [inline]
percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline]
percpu_ref_switch_to_atomic_rcu+0x3e7/0x520 lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:227 [inline]
rcu_do_batch kernel/rcu/tree.c:2475 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2788 [inline]
rcu_core+0x928/0x1390 kernel/rcu/tree.c:2769
__do_softirq+0x266/0x95a kernel/softirq.c:293
invoke_softirq kernel/softirq.c:374 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:414
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
__sanitizer_cov_trace_const_cmp1+0x5/0x20 kernel/kcov.c:175
tlb_flush_mmu_free+0x4e/0x120 mm/mmu_gather.c:74
zap_pte_range mm/memory.c:1158 [inline]
zap_pmd_range mm/memory.c:1193 [inline]
zap_pud_range mm/memory.c:1222 [inline]
zap_p4d_range mm/memory.c:1243 [inline]
unmap_page_range+0x180e/0x2330 mm/memory.c:1264
unmap_single_vma+0x19d/0x300 mm/memory.c:1309
unmap_vmas+0x115/0x250 mm/memory.c:1340
exit_mmap+0x2c2/0x530 mm/mmap.c:3138
__mmput kernel/fork.c:1046 [inline]
mmput+0x15f/0x4c0 kernel/fork.c:1067
exit_mm kernel/exit.c:546 [inline]
do_exit+0x816/0x2fa0 kernel/exit.c:863
do_group_exit+0x135/0x370 kernel/exit.c:980
get_signal+0x399/0x1d50 kernel/signal.c:2577
do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
prepare_exit_to_usermode+0x279/0x2e0 arch/x86/entry/common.c:197
retint_user+0x8/0x18
INITIAL USE at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
_raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0x2d/0x4a0 fs/aio.c:621
percpu_ref_put_many include/linux/percpu-refcount.h:285 [inline]
percpu_ref_put include/linux/percpu-refcount.h:301 [inline]
percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline]
percpu_ref_switch_to_atomic_rcu+0x3e7/0x520 lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:227 [inline]
rcu_do_batch kernel/rcu/tree.c:2475 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2788 [inline]
rcu_core+0x928/0x1390 kernel/rcu/tree.c:2769
__do_softirq+0x266/0x95a kernel/softirq.c:293
invoke_softirq kernel/softirq.c:374 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:414
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
__sanitizer_cov_trace_const_cmp1+0x5/0x20 kernel/kcov.c:175
tlb_flush_mmu_free+0x4e/0x120 mm/mmu_gather.c:74
zap_pte_range mm/memory.c:1158 [inline]
zap_pmd_range mm/memory.c:1193 [inline]
zap_pud_range mm/memory.c:1222 [inline]
zap_p4d_range mm/memory.c:1243 [inline]
unmap_page_range+0x180e/0x2330 mm/memory.c:1264
unmap_single_vma+0x19d/0x300 mm/memory.c:1309
unmap_vmas+0x115/0x250 mm/memory.c:1340
exit_mmap+0x2c2/0x530 mm/mmap.c:3138
__mmput kernel/fork.c:1046 [inline]
mmput+0x15f/0x4c0 kernel/fork.c:1067
exit_mm kernel/exit.c:546 [inline]
do_exit+0x816/0x2fa0 kernel/exit.c:863
do_group_exit+0x135/0x370 kernel/exit.c:980
get_signal+0x399/0x1d50 kernel/signal.c:2577
do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
prepare_exit_to_usermode+0x279/0x2e0 arch/x86/entry/common.c:197
retint_user+0x8/0x18
}
... key at: [<ffffffff8a5e8ea0>] __key.52644+0x0/0x40
... acquired at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
aio_poll fs/aio.c:1762 [inline]
__io_submit_one fs/aio.c:1868 [inline]
io_submit_one+0xe35/0x1cf0 fs/aio.c:1901
__do_sys_io_submit fs/aio.c:1946 [inline]
__se_sys_io_submit fs/aio.c:1916 [inline]
__x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1916
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> (&ctx->fd_wqh){....} {
INITIAL USE at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
__wake_up_common_lock+0xc7/0x190 kernel/sched/wait.c:120
__wake_up+0xe/0x10 kernel/sched/wait.c:145
handle_userfault+0x925/0x18c0 fs/userfaultfd.c:487
do_anonymous_page mm/memory.c:2941 [inline]
handle_pte_fault mm/memory.c:3807 [inline]
__handle_mm_fault+0x361d/0x3ec0 mm/memory.c:3933
handle_mm_fault+0x43f/0xb30 mm/memory.c:3970
do_user_addr_fault arch/x86/mm/fault.c:1475 [inline]
__do_page_fault+0x5ef/0xda0 arch/x86/mm/fault.c:1541
do_page_fault+0x71/0x581 arch/x86/mm/fault.c:1572
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143
__get_user_4+0x21/0x30 arch/x86/lib/getuser.S:76
sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3120
__sys_setsockopt+0x180/0x280 net/socket.c:2046
__do_sys_setsockopt net/socket.c:2057 [inline]
__se_sys_setsockopt net/socket.c:2054 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:2054
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
}
... key at: [<ffffffff8a5e8c20>] __key.45453+0x0/0x40
... acquired at:
check_prevs_add kernel/locking/lockdep.c:2333 [inline]
validate_chain kernel/locking/lockdep.c:2714 [inline]
__lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3701
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198
do_loop_readv_writev fs/read_write.c:700 [inline]
do_loop_readv_writev fs/read_write.c:687 [inline]
do_iter_read+0x4a9/0x660 fs/read_write.c:921
vfs_readv+0xf0/0x160 fs/read_write.c:983
do_readv+0xf6/0x290 fs/read_write.c:1016
__do_sys_readv fs/read_write.c:1103 [inline]
__se_sys_readv fs/read_write.c:1100 [inline]
__x64_sys_readv+0x75/0xb0 fs/read_write.c:1100
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

the dependencies between the lock to be acquired
and SOFTIRQ-irq-unsafe lock:
-> (&ctx->fault_pending_wqh){+.+.} {
HARDIRQ-ON-W at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
handle_userfault+0x58e/0x18c0 fs/userfaultfd.c:461
do_anonymous_page mm/memory.c:2941 [inline]
handle_pte_fault mm/memory.c:3807 [inline]
__handle_mm_fault+0x361d/0x3ec0 mm/memory.c:3933
handle_mm_fault+0x43f/0xb30 mm/memory.c:3970
do_user_addr_fault arch/x86/mm/fault.c:1475 [inline]
__do_page_fault+0x5ef/0xda0 arch/x86/mm/fault.c:1541
do_page_fault+0x71/0x581 arch/x86/mm/fault.c:1572
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143
__get_user_4+0x21/0x30 arch/x86/lib/getuser.S:76
sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3120
__sys_setsockopt+0x180/0x280 net/socket.c:2046
__do_sys_setsockopt net/socket.c:2057 [inline]
__se_sys_setsockopt net/socket.c:2054 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:2054
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
SOFTIRQ-ON-W at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
handle_userfault+0x58e/0x18c0 fs/userfaultfd.c:461
do_anonymous_page mm/memory.c:2941 [inline]
handle_pte_fault mm/memory.c:3807 [inline]
__handle_mm_fault+0x361d/0x3ec0 mm/memory.c:3933
handle_mm_fault+0x43f/0xb30 mm/memory.c:3970
do_user_addr_fault arch/x86/mm/fault.c:1475 [inline]
__do_page_fault+0x5ef/0xda0 arch/x86/mm/fault.c:1541
do_page_fault+0x71/0x581 arch/x86/mm/fault.c:1572
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143
__get_user_4+0x21/0x30 arch/x86/lib/getuser.S:76
sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3120
__sys_setsockopt+0x180/0x280 net/socket.c:2046
__do_sys_setsockopt net/socket.c:2057 [inline]
__se_sys_setsockopt net/socket.c:2054 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:2054
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
INITIAL USE at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
handle_userfault+0x58e/0x18c0 fs/userfaultfd.c:461
do_anonymous_page mm/memory.c:2941 [inline]
handle_pte_fault mm/memory.c:3807 [inline]
__handle_mm_fault+0x361d/0x3ec0 mm/memory.c:3933
handle_mm_fault+0x43f/0xb30 mm/memory.c:3970
do_user_addr_fault arch/x86/mm/fault.c:1475 [inline]
__do_page_fault+0x5ef/0xda0 arch/x86/mm/fault.c:1541
do_page_fault+0x71/0x581 arch/x86/mm/fault.c:1572
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143
__get_user_4+0x21/0x30 arch/x86/lib/getuser.S:76
sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3120
__sys_setsockopt+0x180/0x280 net/socket.c:2046
__do_sys_setsockopt net/socket.c:2057 [inline]
__se_sys_setsockopt net/socket.c:2054 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:2054
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
}
... key at: [<ffffffff8a5e8ce0>] __key.45450+0x0/0x40
... acquired at:
check_prevs_add kernel/locking/lockdep.c:2333 [inline]
validate_chain kernel/locking/lockdep.c:2714 [inline]
__lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3701
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198
do_loop_readv_writev fs/read_write.c:700 [inline]
do_loop_readv_writev fs/read_write.c:687 [inline]
do_iter_read+0x4a9/0x660 fs/read_write.c:921
vfs_readv+0xf0/0x160 fs/read_write.c:983
do_readv+0xf6/0x290 fs/read_write.c:1016
__do_sys_readv fs/read_write.c:1103 [inline]
__se_sys_readv fs/read_write.c:1100 [inline]
__x64_sys_readv+0x75/0xb0 fs/read_write.c:1100
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

stack backtrace:
CPU: 0 PID: 1446 Comm: syz-executor.3 Not tainted 5.1.0-rc2+ #40
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+0x172/0x1f0 lib/dump_stack.c:113
print_bad_irq_dependency kernel/locking/lockdep.c:1920 [inline]
check_usage.cold+0x60f/0x940 kernel/locking/lockdep.c:1952
check_irq_usage kernel/locking/lockdep.c:1997 [inline]
check_prev_add_irq kernel/locking/lockdep_states.h:8 [inline]
check_prev_add.constprop.0+0x2e3/0x23c0 kernel/locking/lockdep.c:2225
check_prevs_add kernel/locking/lockdep.c:2333 [inline]
validate_chain kernel/locking/lockdep.c:2714 [inline]
__lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3701
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198
do_loop_readv_writev fs/read_write.c:700 [inline]
do_loop_readv_writev fs/read_write.c:687 [inline]
do_iter_read+0x4a9/0x660 fs/read_write.c:921
vfs_readv+0xf0/0x160 fs/read_write.c:983
do_readv+0xf6/0x290 fs/read_write.c:1016
__do_sys_readv fs/read_write.c:1103 [inline]
__se_sys_readv fs/read_write.c:1100 [inline]
__x64_sys_readv+0x75/0xb0 fs/read_write.c:1100
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458209
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f08b0ce8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000013
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458209
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f08b0ce96d4
R13: 00000000004c4cfc R14: 00000000004d8ce0 R15: 00000000ffffffff

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

Next message: Oscar Salvador: "Re: [PATCH v3 1/2] mm/sparse: Clean up the obsolete code comment"
Previous message: Pavel Machek: "Re: kernfs: can read/write method grow buffer size?"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]