Subject: [syzbot] [bpf?] possible deadlock in htab_lock_bucket (2)

From: syzbot <[email-masked]>
Date: Mon, 05 Aug 2024 03:05:20 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    3d650ab5e7d9 selftests/bpf: Fix a btf_dump selftest failure
git tree:       bpf-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1628e483980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5efb917b1462a973
dashboard link: https://syzkaller.appspot.com/bug?extid=ee7551b0640c5471e610
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=117de4e5980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=142e86bd980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/630e210de8d9/disk-3d650ab5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3576ca35748a/vmlinux-3d650ab5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5b33f099abfa/bzImage-3d650ab5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

======================================================
WARNING: possible circular locking dependency detected
6.10.0-syzkaller-12666-g3d650ab5e7d9 #0 Not tainted
------------------------------------------------------
strace-static-x/5224 is trying to acquire lock:
ffff888024c4e218 (&htab->lockdep_key){....}-{2:2}, at: htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167

but task is already holding lock:
ffff888023c33188 (&htab->lockdep_key#3){....}-{2:2}, at: htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&htab->lockdep_key#3){....}-{2:2}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167
       htab_lru_map_delete_elem+0x1f1/0x700 kernel/bpf/hashtab.c:1462
       bpf_prog_6f5f05285f674219+0x43/0x4c
       bpf_dispatcher_nop_func include/linux/bpf.h:1252 [inline]
       __bpf_prog_run include/linux/filter.h:691 [inline]
       bpf_prog_run include/linux/filter.h:698 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2406 [inline]
       bpf_trace_run2+0x2ec/0x540 kernel/trace/bpf_trace.c:2447
       __traceiter_contention_begin+0x7b/0xb0 include/trace/events/lock.h:95
       trace_contention_begin+0x117/0x140 include/trace/events/lock.h:95
       __pv_queued_spin_lock_slowpath+0x114/0xdc0 kernel/locking/qspinlock.c:402
       pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
       queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
       queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
       do_raw_spin_lock+0x272/0x370 kernel/locking/spinlock_debug.c:116
       htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167
       htab_lru_map_delete_elem+0x1f1/0x700 kernel/bpf/hashtab.c:1462
       0xffffffffa000204b
       bpf_dispatcher_nop_func include/linux/bpf.h:1252 [inline]
       __bpf_prog_run include/linux/filter.h:691 [inline]
       bpf_prog_run include/linux/filter.h:698 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2406 [inline]
       bpf_trace_run2+0x2ec/0x540 kernel/trace/bpf_trace.c:2447
       __traceiter_contention_begin+0x7b/0xb0 include/trace/events/lock.h:95
       trace_contention_begin+0xf5/0x120 include/trace/events/lock.h:95
       __mutex_lock_common kernel/locking/mutex.c:610 [inline]
       __mutex_lock+0x147/0xd70 kernel/locking/mutex.c:752
       pipe_read+0x12a/0x13e0 fs/pipe.c:264
       new_sync_read fs/read_write.c:395 [inline]
       vfs_read+0x9bd/0xbc0 fs/read_write.c:476
       ksys_read+0x1a0/0x2c0 fs/read_write.c:619
       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

-> #0 (&htab->lockdep_key){....}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3133 [inline]
       check_prevs_add kernel/locking/lockdep.c:3252 [inline]
       validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
       __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167
       htab_lru_map_delete_elem+0x1f1/0x700 kernel/bpf/hashtab.c:1462
       0xffffffffa000204b
       bpf_dispatcher_nop_func include/linux/bpf.h:1252 [inline]
       __bpf_prog_run include/linux/filter.h:691 [inline]
       bpf_prog_run include/linux/filter.h:698 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2406 [inline]
       bpf_trace_run2+0x2ec/0x540 kernel/trace/bpf_trace.c:2447
       __traceiter_contention_begin+0x7b/0xb0 include/trace/events/lock.h:95
       trace_contention_begin+0x117/0x140 include/trace/events/lock.h:95
       __pv_queued_spin_lock_slowpath+0x114/0xdc0 kernel/locking/qspinlock.c:402
       pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
       queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
       queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
       do_raw_spin_lock+0x272/0x370 kernel/locking/spinlock_debug.c:116
       htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167
       htab_lru_map_delete_elem+0x1f1/0x700 kernel/bpf/hashtab.c:1462
       bpf_prog_6f5f05285f674219+0x43/0x4c
       bpf_dispatcher_nop_func include/linux/bpf.h:1252 [inline]
       __bpf_prog_run include/linux/filter.h:691 [inline]
       bpf_prog_run include/linux/filter.h:698 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2406 [inline]
       bpf_trace_run2+0x2ec/0x540 kernel/trace/bpf_trace.c:2447
       __traceiter_contention_begin+0x7b/0xb0 include/trace/events/lock.h:95
       trace_contention_begin+0xf5/0x120 include/trace/events/lock.h:95
       __mutex_lock_common kernel/locking/mutex.c:610 [inline]
       __mutex_lock+0x147/0xd70 kernel/locking/mutex.c:752
       pipe_write+0x1c9/0x1a40 fs/pipe.c:455
       new_sync_write fs/read_write.c:497 [inline]
       vfs_write+0xa72/0xc90 fs/read_write.c:590
       ksys_write+0x1a0/0x2c0 fs/read_write.c:643
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&htab->lockdep_key#3);
                               lock(&htab->lockdep_key);
                               lock(&htab->lockdep_key#3);
  lock(&htab->lockdep_key);

 *** DEADLOCK ***

4 locks held by strace-static-x/5224:
 #0: ffff88802c11bc68 (&pipe->mutex){+.+.}-{3:3}, at: pipe_write+0x1c9/0x1a40 fs/pipe.c:455
 #1: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
 #1: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #1: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2405 [inline]
 #1: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1fc/0x540 kernel/trace/bpf_trace.c:2447
 #2: ffff888023c33188 (&htab->lockdep_key#3){....}-{2:2}, at: htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167
 #3: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
 #3: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #3: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2405 [inline]
 #3: ffffffff8e937660 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1fc/0x540 kernel/trace/bpf_trace.c:2447

stack backtrace:
CPU: 0 UID: 0 PID: 5224 Comm: strace-static-x Not tainted 6.10.0-syzkaller-12666-g3d650ab5e7d9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2186
 check_prev_add kernel/locking/lockdep.c:3133 [inline]
 check_prevs_add kernel/locking/lockdep.c:3252 [inline]
 validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 htab_lock_bucket+0x1a4/0x370 kernel/bpf/hashtab.c:167
 htab_lru_map_delete_elem+0x1f1/0x700 kernel/bpf/hashtab.c:1462
 </TASK>

---
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