Couple of fixes that came from recent discussion [0] on commit
7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down").
This series doesn't address the sleeping while holding a spinlock
problem. We're still trying to decide how to fix that [1].
Until then sockmap users might see the following warnings:
| BUG: sleeping function called from invalid context at net/core/sock.c:2935
| in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 62, name: kworker/0:1
| 3 locks held by kworker/0:1/62:
| #0: ffff88813b019748 ((wq_completion)events){+.+.}, at: process_one_work+0x1d7/0x5e0
| #1: ffffc900000abe50 ((work_completion)(&map->work)){+.+.}, at: process_one_work+0x1d7/0x5e0
| #2: ffff8881381f6df8 (&stab->lock){+...}, at: sock_map_free+0x26/0x180
| CPU: 0 PID: 62 Comm: kworker/0:1 Not tainted 5.5.0-04008-g7b083332376e #454
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
| Workqueue: events bpf_map_free_deferred
| Call Trace:
| dump_stack+0x71/0xa0
| ___might_sleep.cold+0xa6/0xb6
| lock_sock_nested+0x28/0x90
| sock_map_free+0x5f/0x180
| bpf_map_free_deferred+0x58/0x80
| process_one_work+0x260/0x5e0
| worker_thread+0x4d/0x3e0
| kthread+0x108/0x140
| ? process_one_work+0x5e0/0x5e0
| ? kthread_park+0x90/0x90
| ret_from_fork+0x3a/0x50
|
| ======================================================
| WARNING: possible circular locking dependency detected
| 5.5.0-04008-g7b083332376e #454 Tainted: G W
| ------------------------------------------------------
| kworker/0:1/62 is trying to acquire lock:
| ffff88813b280130 (sk_lock-AF_INET){+.+.}, at: sock_map_free+0x5f/0x180
|
| but task is already holding lock:
| ffff8881381f6df8 (&stab->lock){+...}, at: sock_map_free+0x26/0x180
|
| which lock already depends on the new lock.
|
|
| the existing dependency chain (in reverse order) is:
|
| -> #1 (&stab->lock){+...}:
| _raw_spin_lock_bh+0x39/0x80
| sock_map_update_common+0xdc/0x300
| sock_map_update_elem+0xc3/0x150
| __do_sys_bpf+0x1285/0x1620
| do_syscall_64+0x6d/0x690
| entry_SYSCALL_64_after_hwframe+0x49/0xbe
|
| -> #0 (sk_lock-AF_INET){+.+.}:
| __lock_acquire+0xe2f/0x19f0
| lock_acquire+0x95/0x190
| lock_sock_nested+0x6b/0x90
| sock_map_free+0x5f/0x180
| bpf_map_free_deferred+0x58/0x80
| process_one_work+0x260/0x5e0
| worker_thread+0x4d/0x3e0
| kthread+0x108/0x140
| ret_from_fork+0x3a/0x50
|
| other info that might help us debug this:
|
| Possible unsafe locking scenario:
|
| CPU0 CPU1
| ---- ----
| lock(&stab->lock);
| lock(sk_lock-AF_INET);
| lock(&stab->lock);
| lock(sk_lock-AF_INET);
|
| *** DEADLOCK ***
|
| 3 locks held by kworker/0:1/62:
| #0: ffff88813b019748 ((wq_completion)events){+.+.}, at: process_one_work+0x1d7/0x5e0
| #1: ffffc900000abe50 ((work_completion)(&map->work)){+.+.}, at: process_one_work+0x1d7/0x5e0
| #2: ffff8881381f6df8 (&stab->lock){+...}, at: sock_map_free+0x26/0x180
|
| stack backtrace:
| CPU: 0 PID: 62 Comm: kworker/0:1 Tainted: G W 5.5.0-04008-g7b083332376e #454
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
| Workqueue: events bpf_map_free_deferred
| Call Trace:
| dump_stack+0x71/0xa0
| check_noncircular+0x176/0x190
| __lock_acquire+0xe2f/0x19f0
| lock_acquire+0x95/0x190
| ? sock_map_free+0x5f/0x180
| lock_sock_nested+0x6b/0x90
| ? sock_map_free+0x5f/0x180
| sock_map_free+0x5f/0x180
| bpf_map_free_deferred+0x58/0x80
| process_one_work+0x260/0x5e0
| worker_thread+0x4d/0x3e0
| kthread+0x108/0x140
| ? process_one_work+0x5e0/0x5e0
| ? kthread_park+0x90/0x90
| ret_from_fork+0x3a/0x50
[0] https://lore.kernel.org/bpf/8736boor55.fsf@xxxxxxxxxxxxxx/
[1] https://lore.kernel.org/bpf/5e3ba96ca7889_6b512aafe4b145b812@john-XPS-13-9370.notmuch/
Jakub Sitnicki (3):
bpf, sockmap: Don't sleep while holding RCU lock on tear-down
bpf, sockhash: synchronize_rcu before free'ing map
selftests/bpf: Test freeing sockmap/sockhash with a socket in it
net/core/sock_map.c | 12 ++-
.../selftests/bpf/prog_tests/sockmap_basic.c | 74 +++++++++++++++++++
2 files changed, 82 insertions(+), 4 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
--
2.24.1
