Re: [PATCH bpf-next v2] selftests/bpf: fix incorrect fcntl call (test_sockmap.c)

From: Alexei Starovoitov
Date: Thu Aug 25 2022 - 22:07:25 EST

On Wed, Aug 24, 2022 at 7:11 PM Qiao Ma <mqaio@xxxxxxxxxxxxxxxxx> wrote:
>
> In test_sockmap.c, the testcase sets socket nonblock first, and then
> calls select() and recvmsg() to receive data.
> If some error occur, nonblock setting will make recvmsg() return
> immediately, rather than blocking forever.
>
> However, the way to call fcntl() to set nonblock is wrong.
> To set socket noblock, we need to use
> > fcntl(fd, F_SETFL, O_NONBLOCK);
> rather than:
> > fcntl(fd, O_NONBLOCK);
>
> Signed-off-by: Qiao Ma <mqaio@xxxxxxxxxxxxxxxxx>
> ---
> tools/testing/selftests/bpf/test_sockmap.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/test_sockmap.c b/tools/testing/selftests/bpf/test_sockmap.c
> index 0fbaccdc8861..abb4102f33b0 100644
> --- a/tools/testing/selftests/bpf/test_sockmap.c
> +++ b/tools/testing/selftests/bpf/test_sockmap.c
> @@ -598,7 +598,12 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
> struct timeval timeout;
> fd_set w;
>
> - fcntl(fd, fd_flags);
> + err = fcntl(fd, F_SETFL, fd_flags);
> + if (err < 0) {
> + perror("fcntl failed");
> + goto out_errno;
> + }
> +

John, Jakub,

Please review this.
Unfortunately test_sockmap (and sockmap kernel) is broken
before and after this patch,
so I'm hesitant to apply it not to make thing harder to debug.
Here is what I see:
# ./test_sockmap
recv failed(): Bad address
rx thread exited with err 1.
recv failed(): Bad address
rx thread exited with err 1.
recv failed(): Bad address
rx thread exited with err 1.
# 4/ 6 sockmap::txmsg test ingress redirect:FAIL
detected skb data error with skb ingress update @iov[0]:0 "00 00 00
00" != "PASS"
data verify msg failed: Unknown error -5
rx thread exited with err 1.
[ 16.735850] ------------[ cut here ]------------
[ 16.736195] WARNING: CPU: 3 PID: 1480 at net/core/stream.c:205
sk_stream_kill_queues+0x18a/0x1a0
[ 16.736799] Modules linked in:
[ 16.737007] CPU: 3 PID: 1480 Comm: test_sockmap Not tainted
5.19.0-14050-g343949e10798 #4212
[ 16.737543] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[ 16.738522] RIP: 0010:sk_stream_kill_queues+0x18a/0x1a0
[ 16.738883] Code: 41 5f c3 89 ee 48 89 df e8 13 69 fe ff 4c 89 e7
e8 db 01 4f ff 8b ab 28 02 00 00 eb c1 0f 0b e9 62 ff ff ff 0f 0b 85
ed 74 ce <0f> 0b 5b 5d 41 5c 41 5d 41 5e 41 5f c3 66 0f 1f 84 00 00 00
00 00
[ 16.740082] RSP: 0018:ffff888118007ab8 EFLAGS: 00010206
[ 16.740435] RAX: 0000000000000000 RBX: ffff8881174b2400 RCX: ffffffff81f5d47a
[ 16.740915] RDX: 0000000000000003 RSI: dffffc0000000000 RDI: ffff8881174b2670
[ 16.741374] RBP: 0000000000000b00 R08: fffffbfff08cfbdf R09: fffffbfff08cfbdf
[ 16.741841] R10: ffffffff8467def7 R11: fffffbfff08cfbde R12: ffff8881174b2628
[ 16.742298] R13: ffffffff85c13c00 R14: ffff88810611d824 R15: ffff8881174b25c8
[ 16.742768] FS: 00007f937403c400(0000) GS:ffff888628f80000(0000)
knlGS:0000000000000000
[ 16.743283] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 16.743657] CR2: 00007f937403c378 CR3: 0000000125983005 CR4: 00000000003706e0
[ 16.744124] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 16.744584] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 16.745065] Call Trace:
[ 16.745241] <TASK>
[ 16.745401] inet_csk_destroy_sock+0x9f/0x1c0
[ 16.745707] tcp_rcv_state_process+0x1a84/0x2120
[ 16.746013] ? lock_release+0x3b0/0x3b0
[ 16.746271] ? tcp_established_options+0x189/0x300
[ 16.746592] ? tcp_finish_connect+0x240/0x240
[ 16.746894] ? rcu_read_lock_bh_held+0xa0/0xa0
[ 16.747190] ? rcu_read_lock_held_common+0x1a/0x50
[ 16.747505] ? rcu_read_lock_sched_held+0x56/0xc0
[ 16.747823] ? rcu_read_lock_held_common+0x1a/0x50
[ 16.748139] ? lock_release+0xad/0x3b0
[ 16.748390] ? __release_sock+0x83/0x150
[ 16.748646] ? lock_downgrade+0x360/0x360
[ 16.748932] ? lock_acquire+0xab/0x380
[ 16.749187] ? lock_downgrade+0x360/0x360
[ 16.749440] ? tcp_v4_do_rcv+0x195/0x4f0
[ 16.749696] tcp_v4_do_rcv+0x195/0x4f0
[ 16.749933] ? trace_hardirqs_on+0x2d/0xe0
[ 16.750194] __release_sock+0xb9/0x150
...
[ 213.529908] ------------[ cut here ]------------
[ 213.530232] page_counter underflow: -7 nr_pages=31
[ 213.530571] WARNING: CPU: 1 PID: 1925 at mm/page_counter.c:57
page_counter_cancel+0x56/0x80
[ 213.531125] Modules linked in:
[ 213.531332] CPU: 1 PID: 1925 Comm: test_sockmap Tainted: G W
5.19.0-14050-g343949e10798 #4212
[ 213.531989] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[ 213.532734] RIP: 0010:page_counter_cancel+0x56/0x80
[ 213.533070] Code: 0a 48 89 df 5b 5d e9 89 fe ff ff 80 3d d1 b6 1e
03 00 75 18 48 89 ea 48 c7 c7 60 6a b3 82 c6 05 be b6 1e 03 01 e8 aa
aa 0b 01 <0f> 0b be 08 00 00 00 48 89 df e8 bb 22 fe ff 48 89 df e8 13
1a fe
[ 213.534259] RSP: 0018:ffff88811ae2f8b0 EFLAGS: 00010086
[ 213.534607] RAX: 0000000000000000 RBX: ffff888100c08120 RCX: 0000000000000000
[ 213.535071] RDX: 0000000000000027 RSI: dffffc0000000000 RDI: ffffed10235c5f0c
[ 213.535535] RBP: 000000000000001f R08: ffffed10c51d4ee6 R09: ffffed10c51d4ee6
[ 213.536000] R10: ffff888628ea772b R11: ffffed10c51d4ee5 R12: ffff888628eb5d18
[ 213.536479] R13: ffff888628eb5d10 R14: ffff888628eb5d18 R15: 000000000000001f
[ 213.536953] FS: 00007fe0f0478400(0000) GS:ffff888628e80000(0000)
knlGS:0000000000000000
[ 213.537463] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 213.537858] CR2: 00007fe0f04786d0 CR3: 000000011ab33004 CR4: 00000000003706e0
[ 213.538325] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 213.538838] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 213.539318] Call Trace:
[ 213.539488] <TASK>
[ 213.539635] page_counter_uncharge+0x1d/0x40
[ 213.539927] drain_stock.isra.54+0x5d/0xb0
[ 213.540200] __refill_stock+0x42/0xb0
[ 213.540451] refill_stock+0xc1/0x1c0
[ 213.540688] try_charge_memcg+0xb2e/0xb50

and test_sockmap 'hangs' (or doing something for long time) after
#31/ 6 sockhash:ktls:txmsg test drop:OK