diff options
| author | Yonghong Song <yhs@fb.com> | 2021-08-19 18:52:09 +0300 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2021-08-19 21:49:19 +0300 |
| commit | 594286b7574c6e8217b1c233cc0d0650f2268a77 (patch) | |
| tree | ed8fa37bf52ea943044d1aca1a0755fb2b97d339 /kernel/events | |
| parent | f9dabe016b63c9629e152bf876c126c29de223cb (diff) | |
| download | linux-594286b7574c6e8217b1c233cc0d0650f2268a77.tar.xz | |
bpf: Fix NULL event->prog pointer access in bpf_overflow_handler
Andrii reported that libbpf CI hit the following oops when
running selftest send_signal:
[ 1243.160719] BUG: kernel NULL pointer dereference, address: 0000000000000030
[ 1243.161066] #PF: supervisor read access in kernel mode
[ 1243.161066] #PF: error_code(0x0000) - not-present page
[ 1243.161066] PGD 0 P4D 0
[ 1243.161066] Oops: 0000 [#1] PREEMPT SMP NOPTI
[ 1243.161066] CPU: 1 PID: 882 Comm: new_name Tainted: G O 5.14.0-rc5 #1
[ 1243.161066] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[ 1243.161066] RIP: 0010:bpf_overflow_handler+0x9a/0x1e0
[ 1243.161066] Code: 5a 84 c0 0f 84 06 01 00 00 be 66 02 00 00 48 c7 c7 6d 96 07 82 48 8b ab 18 05 00 00 e8 df 55 eb ff 66 90 48 8d 75 48 48 89 e7 <ff> 55 30 41 89 c4 e8 fb c1 f0 ff 84 c0 0f 84 94 00 00 00 e8 6e 0f
[ 1243.161066] RSP: 0018:ffffc900000c0d80 EFLAGS: 00000046
[ 1243.161066] RAX: 0000000000000002 RBX: ffff8881002e0dd0 RCX: 00000000b4b47cf8
[ 1243.161066] RDX: ffffffff811dcb06 RSI: 0000000000000048 RDI: ffffc900000c0d80
[ 1243.161066] RBP: 0000000000000000 R08: 0000000000000000 R09: 1a9d56bb00000000
[ 1243.161066] R10: 0000000000000001 R11: 0000000000080000 R12: 0000000000000000
[ 1243.161066] R13: ffffc900000c0e00 R14: ffffc900001c3c68 R15: 0000000000000082
[ 1243.161066] FS: 00007fc0be2d3380(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
[ 1243.161066] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1243.161066] CR2: 0000000000000030 CR3: 0000000104f8e000 CR4: 00000000000006e0
[ 1243.161066] Call Trace:
[ 1243.161066] <IRQ>
[ 1243.161066] __perf_event_overflow+0x4f/0xf0
[ 1243.161066] perf_swevent_hrtimer+0x116/0x130
[ 1243.161066] ? __lock_acquire+0x378/0x2730
[ 1243.161066] ? __lock_acquire+0x372/0x2730
[ 1243.161066] ? lock_is_held_type+0xd5/0x130
[ 1243.161066] ? find_held_lock+0x2b/0x80
[ 1243.161066] ? lock_is_held_type+0xd5/0x130
[ 1243.161066] ? perf_event_groups_first+0x80/0x80
[ 1243.161066] ? perf_event_groups_first+0x80/0x80
[ 1243.161066] __hrtimer_run_queues+0x1a3/0x460
[ 1243.161066] hrtimer_interrupt+0x110/0x220
[ 1243.161066] __sysvec_apic_timer_interrupt+0x8a/0x260
[ 1243.161066] sysvec_apic_timer_interrupt+0x89/0xc0
[ 1243.161066] </IRQ>
[ 1243.161066] asm_sysvec_apic_timer_interrupt+0x12/0x20
[ 1243.161066] RIP: 0010:finish_task_switch+0xaf/0x250
[ 1243.161066] Code: 31 f6 68 90 2a 09 81 49 8d 7c 24 18 e8 aa d6 03 00 4c 89 e7 e8 12 ff ff ff 4c 89 e7 e8 ca 9c 80 00 e8 35 af 0d 00 fb 4d 85 f6 <58> 74 1d 65 48 8b 04 25 c0 6d 01 00 4c 3b b0 a0 04 00 00 74 37 f0
[ 1243.161066] RSP: 0018:ffffc900001c3d18 EFLAGS: 00000282
[ 1243.161066] RAX: 000000000000031f RBX: ffff888104cf4980 RCX: 0000000000000000
[ 1243.161066] RDX: 0000000000000000 RSI: ffffffff82095460 RDI: ffffffff820adc4e
[ 1243.161066] RBP: ffffc900001c3d58 R08: 0000000000000001 R09: 0000000000000001
[ 1243.161066] R10: 0000000000000001 R11: 0000000000080000 R12: ffff88813bd2bc80
[ 1243.161066] R13: ffff8881002e8000 R14: ffff88810022ad80 R15: 0000000000000000
[ 1243.161066] ? finish_task_switch+0xab/0x250
[ 1243.161066] ? finish_task_switch+0x70/0x250
[ 1243.161066] __schedule+0x36b/0xbb0
[ 1243.161066] ? _raw_spin_unlock_irqrestore+0x2d/0x50
[ 1243.161066] ? lockdep_hardirqs_on+0x79/0x100
[ 1243.161066] schedule+0x43/0xe0
[ 1243.161066] pipe_read+0x30b/0x450
[ 1243.161066] ? wait_woken+0x80/0x80
[ 1243.161066] new_sync_read+0x164/0x170
[ 1243.161066] vfs_read+0x122/0x1b0
[ 1243.161066] ksys_read+0x93/0xd0
[ 1243.161066] do_syscall_64+0x35/0x80
[ 1243.161066] entry_SYSCALL_64_after_hwframe+0x44/0xae
The oops can also be reproduced with the following steps:
./vmtest.sh -s
# at qemu shell
cd /root/bpf && while true; do ./test_progs -t send_signal
Further analysis showed that the failure is introduced with
commit b89fbfbb854c ("bpf: Implement minimal BPF perf link").
With the above commit, the following scenario becomes possible:
cpu1 cpu2
hrtimer_interrupt -> bpf_overflow_handler
(due to closing link_fd)
bpf_perf_link_release ->
perf_event_free_bpf_prog ->
perf_event_free_bpf_handler ->
WRITE_ONCE(event->overflow_handler, event->orig_overflow_handler)
event->prog = NULL
bpf_prog_run(event->prog, &ctx)
In the above case, the event->prog is NULL for bpf_prog_run, hence
causing oops.
To fix the issue, check whether event->prog is NULL or not. If it
is, do not call bpf_prog_run. This seems working as the above
reproducible step runs more than one hour and I didn't see any
failures.
Fixes: b89fbfbb854c ("bpf: Implement minimal BPF perf link")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210819155209.1927994-1-yhs@fb.com
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/core.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 2d1e63dd97f2..011cc5069b7b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9920,13 +9920,16 @@ static void bpf_overflow_handler(struct perf_event *event, .data = data, .event = event, }; + struct bpf_prog *prog; int ret = 0; ctx.regs = perf_arch_bpf_user_pt_regs(regs); if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) goto out; rcu_read_lock(); - ret = bpf_prog_run(event->prog, &ctx); + prog = READ_ONCE(event->prog); + if (prog) + ret = bpf_prog_run(prog, &ctx); rcu_read_unlock(); out: __this_cpu_dec(bpf_prog_active); |