[v5.15] possible deadlock in htab_map_delete_elem

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0a51d2d4527b Linux 5.15.173
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10ccc778580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f63d146f1af4415a
dashboard link: https://syzkaller.appspot.com/bug?extid=4c3d16f74f429ff25a21
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/733a95526889/disk-0a51d2d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/409603e5dc40/vmlinux-0a51d2d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2d60efa369ee/bzImage-0a51d2d4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c3d16...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.173-syzkaller #0 Not tainted
------------------------------------------------------
syz.3.625/6441 is trying to acquire lock:
ffff888072dc0da0 (&htab->lockdep_key){..-.}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
ffff888072dc0da0 (&htab->lockdep_key){..-.}-{2:2}, at: htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361

but task is already holding lock:
ffff8880753f3720 (&htab->lockdep_key#2){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
ffff8880753f3720 (&htab->lockdep_key#2){....}-{2:2}, at: htab_map_update_elem+0x245/0x9c0 kernel/bpf/hashtab.c:1082

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&htab->lockdep_key#2){....}-{2:2}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361
bpf_prog_2c29ac5cdc6b1842+0x3a/0xe8c
bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
__bpf_prog_run include/linux/filter.h:628 [inline]
bpf_prog_run include/linux/filter.h:635 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
bpf_trace_run4+0x1ea/0x390 kernel/trace/bpf_trace.c:1917
__bpf_trace_mm_page_alloc+0xba/0xe0 include/trace/events/kmem.h:201
__traceiter_mm_page_alloc+0x35/0x50 include/trace/events/kmem.h:201
trace_mm_page_alloc include/trace/events/kmem.h:201 [inline]
__alloc_pages+0x6e0/0x700 mm/page_alloc.c:5486
__alloc_pages_node include/linux/gfp.h:570 [inline]
alloc_pages_node include/linux/gfp.h:584 [inline]
kmalloc_large_node+0x7c/0x180 mm/slub.c:4421
__kmalloc_node+0x22d/0x390 mm/slub.c:4437
kmalloc_node include/linux/slab.h:614 [inline]
bpf_map_kmalloc_node+0xdb/0x160 kernel/bpf/syscall.c:430
alloc_htab_elem+0x28b/0x920 kernel/bpf/hashtab.c:973
htab_map_update_elem+0x3cb/0x9c0 kernel/bpf/hashtab.c:1106
bpf_map_update_value+0x5d7/0x6c0 kernel/bpf/syscall.c:221
map_update_elem+0x6a0/0x7c0 kernel/bpf/syscall.c:1185
__sys_bpf+0x2fd/0x670 kernel/bpf/syscall.c:4639
__do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&htab->lockdep_key){..-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361
bpf_prog_2c29ac5cdc6b1842+0x3a/0xf8c
bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
__bpf_prog_run include/linux/filter.h:628 [inline]
bpf_prog_run include/linux/filter.h:635 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
bpf_trace_run4+0x1ea/0x390 kernel/trace/bpf_trace.c:1917
__bpf_trace_mm_page_alloc+0xba/0xe0 include/trace/events/kmem.h:201
__traceiter_mm_page_alloc+0x35/0x50 include/trace/events/kmem.h:201
trace_mm_page_alloc include/trace/events/kmem.h:201 [inline]
__alloc_pages+0x6e0/0x700 mm/page_alloc.c:5486
__alloc_pages_node include/linux/gfp.h:570 [inline]
alloc_pages_node include/linux/gfp.h:584 [inline]
kmalloc_large_node+0x7c/0x180 mm/slub.c:4421
__kmalloc_node+0x22d/0x390 mm/slub.c:4437
kmalloc_node include/linux/slab.h:614 [inline]
bpf_map_kmalloc_node+0xdb/0x160 kernel/bpf/syscall.c:430
alloc_htab_elem+0x28b/0x920 kernel/bpf/hashtab.c:973
htab_map_update_elem+0x3cb/0x9c0 kernel/bpf/hashtab.c:1106
bpf_map_update_value+0x5d7/0x6c0 kernel/bpf/syscall.c:221
map_update_elem+0x6a0/0x7c0 kernel/bpf/syscall.c:1185
__sys_bpf+0x2fd/0x670 kernel/bpf/syscall.c:4639
__do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&htab->lockdep_key#2);
lock(&htab->lockdep_key);
lock(&htab->lockdep_key#2);
lock(&htab->lockdep_key);

*** DEADLOCK ***

3 locks held by syz.3.625/6441:
#0: ffffffff8c91fc60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
#1: ffff8880753f3720 (&htab->lockdep_key#2){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
#1: ffff8880753f3720 (&htab->lockdep_key#2){....}-{2:2}, at: htab_map_update_elem+0x245/0x9c0 kernel/bpf/hashtab.c:1082
#2: ffffffff8c91fc60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311

stack backtrace:
CPU: 1 PID: 6441 Comm: syz.3.625 Not tainted 5.15.173-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361
bpf_prog_2c29ac5cdc6b1842+0x3a/0xf8c
bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
__bpf_prog_run include/linux/filter.h:628 [inline]
bpf_prog_run include/linux/filter.h:635 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
bpf_trace_run4+0x1ea/0x390 kernel/trace/bpf_trace.c:1917
__bpf_trace_mm_page_alloc+0xba/0xe0 include/trace/events/kmem.h:201
__traceiter_mm_page_alloc+0x35/0x50 include/trace/events/kmem.h:201
trace_mm_page_alloc include/trace/events/kmem.h:201 [inline]
__alloc_pages+0x6e0/0x700 mm/page_alloc.c:5486
__alloc_pages_node include/linux/gfp.h:570 [inline]
alloc_pages_node include/linux/gfp.h:584 [inline]
kmalloc_large_node+0x7c/0x180 mm/slub.c:4421
__kmalloc_node+0x22d/0x390 mm/slub.c:4437
kmalloc_node include/linux/slab.h:614 [inline]
bpf_map_kmalloc_node+0xdb/0x160 kernel/bpf/syscall.c:430
alloc_htab_elem+0x28b/0x920 kernel/bpf/hashtab.c:973
htab_map_update_elem+0x3cb/0x9c0 kernel/bpf/hashtab.c:1106
bpf_map_update_value+0x5d7/0x6c0 kernel/bpf/syscall.c:221
map_update_elem+0x6a0/0x7c0 kernel/bpf/syscall.c:1185
__sys_bpf+0x2fd/0x670 kernel/bpf/syscall.c:4639
__do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f6ac49cb819
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6ac2843038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f6ac4b82fa0 RCX: 00007f6ac49cb819
RDX: 0000000000000020 RSI: 0000000020000280 RDI: 0000000000000002
RBP: 00007f6ac4a3e75e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6ac4b82fa0 R15: 00007fff1f5131c8
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 0a51d2d4527b Linux 5.15.173
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=12460ee8580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f63d146f1af4415a
dashboard link: https://syzkaller.appspot.com/bug?extid=4c3d16f74f429ff25a21
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=16460ee8580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1652c778580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/733a95526889/disk-0a51d2d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/409603e5dc40/vmlinux-0a51d2d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2d60efa369ee/bzImage-0a51d2d4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c3d16...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.173-syzkaller #0 Not tainted
------------------------------------------------------

syz-executor203/4169 is trying to acquire lock:
ffff888022f56020 (&htab->lockdep_key#2){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
ffff888022f56020 (&htab->lockdep_key#2){....}-{2:2}, at: htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361

but task is already holding lock:

ffff888022f560a0 (&htab->lockdep_key#3){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
ffff888022f560a0 (&htab->lockdep_key#3){....}-{2:2}, at: htab_map_update_elem+0x245/0x9c0 kernel/bpf/hashtab.c:1082

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+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361

bpf_prog_2c29ac5cdc6b1842+0x3a/0xd34

-> #0 (&htab->lockdep_key#2){....}-{2:2}:

check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361

bpf_prog_2c29ac5cdc6b1842+0x3a/0x6b8

lock(&htab->lockdep_key#3);
lock(&htab->lockdep_key#2);
lock(&htab->lockdep_key#3);
lock(&htab->lockdep_key#2);

*** DEADLOCK ***

3 locks held by syz-executor203/4169:

#0: ffffffff8c91fc60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311

#1: ffff888022f560a0 (&htab->lockdep_key#3){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
#1: ffff888022f560a0 (&htab->lockdep_key#3){....}-{2:2}, at: htab_map_update_elem+0x245/0x9c0 kernel/bpf/hashtab.c:1082

#2: ffffffff8c91fc60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311

stack backtrace:

CPU: 0 PID: 4169 Comm: syz-executor203 Not tainted 5.15.173-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
htab_lock_bucket kernel/bpf/hashtab.c:183 [inline]
htab_map_delete_elem+0x1bd/0x560 kernel/bpf/hashtab.c:1361

bpf_prog_2c29ac5cdc6b1842+0x3a/0x6b8

RIP: 0033:0x7ff2c8e36029
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd165a5538 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ff2c8e36029

RDX: 0000000000000020 RSI: 0000000020000280 RDI: 0000000000000002

RBP: 0000000000000000 R08: 00000000000000a0 R09: 00000000000000a0
R10: 00000000000000a0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>


---
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.

[syzbot]

syzbot suspects this issue could be fixed by backporting the following commit:

commit 9f2c6e96c65e6fa1aebef546be0c30a5895fcb37
git tree: upstream
Author: Alexei Starovoitov <a...@kernel.org>
Date: Fri Sep 2 21:10:58 2022 +0000

bpf: Optimize rcu_barrier usage between hash map and bpf_mem_alloc.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=136b30f8580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f63d146f1af4415a
dashboard link: https://syzkaller.appspot.com/bug?extid=4c3d16f74f429ff25a21

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16460ee8580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1652c778580000

Please keep in mind that other backports might be required as well.

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