[syzbot] [bpf?] possible deadlock in htab_map_delete_elem

From: syzbot
Date: Wed Sep 11 2024 - 11:39:04 EST

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Hello,

syzbot found the following issue on:

HEAD commit: b31c44928842 Merge tag 'linux_kselftest-kunit-fixes-6.11-r..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=121a189f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=57042fe37c7ee7c2
dashboard link: https://syzkaller.appspot.com/bug?extid=26bfd0c1cea0b221a4bf
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=101c2bc7980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11f5ba00580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-b31c4492.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f518d8293660/vmlinux-b31c4492.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d06107105268/bzImage-b31c4492.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+26bfd0c1cea0b221a4bf@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.11.0-rc6-syzkaller-00308-gb31c44928842 #0 Not tainted
------------------------------------------------------
syz-executor169/5356 is trying to acquire lock:
ffff888035409940 (&htab->lockdep_key#4){-.-.}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
ffff888035409940 (&htab->lockdep_key#4){-.-.}-{2:2}, at: htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426

but task is already holding lock:
ffff888035408820 (&htab->lockdep_key#2){-.-.}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
ffff888035408820 (&htab->lockdep_key#2){-.-.}-{2:2}, at: htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&htab->lockdep_key#2){-.-.}-{2:2}:
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426
bpf_prog_1a158c95e143a564+0x45/0x4e
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [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+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_contention_end+0xca/0x110 include/trace/events/lock.h:122
__traceiter_contention_end+0x5a/0xa0 include/trace/events/lock.h:122
trace_contention_end.constprop.0+0xea/0x170 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x27e/0xc90 kernel/locking/qspinlock.c:557
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116
htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426
bpf_prog_1a158c95e143a564+0x45/0x4e
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [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+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_contention_end+0xca/0x110 include/trace/events/lock.h:122
__traceiter_contention_end+0x5a/0xa0 include/trace/events/lock.h:122
trace_contention_end+0xce/0x140 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:617 [inline]
__mutex_lock+0x19c/0x9c0 kernel/locking/mutex.c:752
put_rng+0x1a/0xe0 drivers/char/hw_random/core.c:141
rng_dev_read+0x22d/0x720 drivers/char/hw_random/core.c:248
do_loop_readv_writev fs/read_write.c:761 [inline]
do_loop_readv_writev fs/read_write.c:749 [inline]
vfs_readv+0x6cb/0x8a0 fs/read_write.c:934
do_preadv fs/read_write.c:1049 [inline]
__do_sys_preadv fs/read_write.c:1099 [inline]
__se_sys_preadv fs/read_write.c:1094 [inline]
__x64_sys_preadv+0x22b/0x310 fs/read_write.c:1094
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&htab->lockdep_key#4){-.-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3133 [inline]
check_prevs_add kernel/locking/lockdep.c:3252 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
lock_acquire kernel/locking/lockdep.c:5759 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426
bpf_prog_1a158c95e143a564+0x45/0x4e
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [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+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_contention_end+0xca/0x110 include/trace/events/lock.h:122
__traceiter_contention_end+0x5a/0xa0 include/trace/events/lock.h:122
trace_contention_end.constprop.0+0xea/0x170 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x27e/0xc90 kernel/locking/qspinlock.c:557
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116
htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426
bpf_prog_1a158c95e143a564+0x45/0x4e
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [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+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_contention_end+0xca/0x110 include/trace/events/lock.h:122
__traceiter_contention_end+0x5a/0xa0 include/trace/events/lock.h:122
trace_contention_end+0xce/0x140 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:727 [inline]
__mutex_lock+0x281/0x9c0 kernel/locking/mutex.c:752
rng_dev_read+0x128/0x720 drivers/char/hw_random/core.c:218
do_loop_readv_writev fs/read_write.c:761 [inline]
do_loop_readv_writev fs/read_write.c:749 [inline]
vfs_readv+0x6cb/0x8a0 fs/read_write.c:934
do_preadv fs/read_write.c:1049 [inline]
__do_sys_preadv fs/read_write.c:1099 [inline]
__se_sys_preadv fs/read_write.c:1094 [inline]
__x64_sys_preadv+0x22b/0x310 fs/read_write.c:1094
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 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#2);
lock(&htab->lockdep_key#4);
lock(&htab->lockdep_key#2);
lock(&htab->lockdep_key#4);

*** DEADLOCK ***

5 locks held by syz-executor169/5356:
#0: ffffffff8e9fb728 (reading_mutex){+.+.}-{3:3}, at: rng_dev_read+0x128/0x720 drivers/char/hw_random/core.c:218
#1: ffffffff8e9fb6e0 (reading_mutex.wait_lock){+.+.}-{2:2}, at: __mutex_lock_common kernel/locking/mutex.c:706 [inline]
#1: ffffffff8e9fb6e0 (reading_mutex.wait_lock){+.+.}-{2:2}, at: __mutex_lock+0x6ac/0x9c0 kernel/locking/mutex.c:752
#2: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
#2: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#2: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2405 [inline]
#2: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2447
#3: ffff888035408820 (&htab->lockdep_key#2){-.-.}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
#3: ffff888035408820 (&htab->lockdep_key#2){-.-.}-{2:2}, at: htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426
#4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
#4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2405 [inline]
#4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2447

stack backtrace:
CPU: 0 UID: 0 PID: 5356 Comm: syz-executor169 Not tainted 6.11.0-rc6-syzkaller-00308-gb31c44928842 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
check_noncircular+0x31a/0x400 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 kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
lock_acquire kernel/locking/lockdep.c:5759 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426
bpf_prog_1a158c95e143a564+0x45/0x4e
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [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+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_contention_end+0xca/0x110 include/trace/events/lock.h:122
__traceiter_contention_end+0x5a/0xa0 include/trace/events/lock.h:122
trace_contention_end.constprop.0+0xea/0x170 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x27e/0xc90 kernel/locking/qspinlock.c:557
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116
htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
htab_map_delete_elem+0x1c8/0x730 kernel/bpf/hashtab.c:1426
bpf_prog_1a158c95e143a564+0x45/0x4e
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [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+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_contention_end+0xca/0x110 include/trace/events/lock.h:122
__traceiter_contention_end+0x5a/0xa0 include/trace/events/lock.h:122
trace_contention_end+0xce/0x140 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:727 [inline]
__mutex_lock+0x281/0x9c0 kernel/locking/mutex.c:752
rng_dev_read+0x128/0x720 drivers/char/hw_random/core.c:218
do_loop_readv_writev fs/read_write.c:761 [inline]
do_loop_readv_writev fs/read_write.c:749 [inline]
vfs_readv+0x6cb/0x8a0 fs/read_write.c:934
do_preadv fs/read_write.c:1049 [inline]
__do_sys_preadv fs/read_write.c:1099 [inline]
__se_sys_preadv fs/read_write.c:1094 [inline]
__x64_sys_preadv+0x22b/0x310 fs/read_write.c:1094
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa70184cea9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 71 19 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa701805218 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007fa7018dc1a8 RCX: 00007fa70184cea9
RDX: 0000000000000001 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00007fa7018dc1a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa7018a325c
R13: 7277682f7665642f R14: 00646e655f6e6f69 R15: 69746e65746e6f63
</TASK>

---
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Next message: Dave Hansen: "Re: [PATCH v6 0/6] x86/tdx: Allow MMIO instructions from userspace"
Previous message: Alejandro Lucero Palau: "Re: [PATCH V4 11/12] bnxt_en: Add TPH support in BNXT driver"
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