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Getting the following splat [1] with CONFIG_DEBUG_NET=y and this
reproducer [2]. Problem seems to be that classifiers clear 'struct
tcf_result::drop_reason', thereby triggering the warning in
__kfree_skb_reason() due to reason being 'SKB_NOT_DROPPED_YET' (0).
Fixed by disambiguating a legit error from a verdict with a bogus drop_reason
[1]
WARNING: CPU: 0 PID: 181 at net/core/skbuff.c:1082 kfree_skb_reason+0x38/0x130
Modules linked in:
CPU: 0 PID: 181 Comm: mausezahn Not tainted 6.6.0-rc6-custom-ge43e6d9582e0 #682
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc37 04/01/2014
RIP: 0010:kfree_skb_reason+0x38/0x130
[...]
Call Trace:
<IRQ>
__netif_receive_skb_core.constprop.0+0x837/0xdb0
__netif_receive_skb_one_core+0x3c/0x70
process_backlog+0x95/0x130
__napi_poll+0x25/0x1b0
net_rx_action+0x29b/0x310
__do_softirq+0xc0/0x29b
do_softirq+0x43/0x60
</IRQ>
[2]
ip link add name veth0 type veth peer name veth1
ip link set dev veth0 up
ip link set dev veth1 up
tc qdisc add dev veth1 clsact
tc filter add dev veth1 ingress pref 1 proto all flower dst_mac 00:11:22:33:44:55 action drop
mausezahn veth0 -a own -b 00:11:22:33:44:55 -q -c 1
Ido reported:
[...] getting the following splat [1] with CONFIG_DEBUG_NET=y and this
reproducer [2]. Problem seems to be that classifiers clear 'struct
tcf_result::drop_reason', thereby triggering the warning in
__kfree_skb_reason() due to reason being 'SKB_NOT_DROPPED_YET' (0). [...]
[1]
WARNING: CPU: 0 PID: 181 at net/core/skbuff.c:1082 kfree_skb_reason+0x38/0x130
Modules linked in:
CPU: 0 PID: 181 Comm: mausezahn Not tainted 6.6.0-rc6-custom-ge43e6d9582e0 #682
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc37 04/01/2014
RIP: 0010:kfree_skb_reason+0x38/0x130
[...]
Call Trace:
<IRQ>
__netif_receive_skb_core.constprop.0+0x837/0xdb0
__netif_receive_skb_one_core+0x3c/0x70
process_backlog+0x95/0x130
__napi_poll+0x25/0x1b0
net_rx_action+0x29b/0x310
__do_softirq+0xc0/0x29b
do_softirq+0x43/0x60
</IRQ>
[2]
#!/bin/bash
ip link add name veth0 type veth peer name veth1
ip link set dev veth0 up
ip link set dev veth1 up
tc qdisc add dev veth1 clsact
tc filter add dev veth1 ingress pref 1 proto all flower dst_mac 00:11:22:33:44:55 action drop
mausezahn veth0 -a own -b 00:11:22:33:44:55 -q -c 1
What happens is that inside most classifiers the tcf_result is copied over
from a filter template e.g. *res = f->res which then implicitly overrides
the prior SKB_DROP_REASON_TC_{INGRESS,EGRESS} default drop code which was
set via sch_handle_{ingress,egress}() for kfree_skb_reason().
Commit text above copied verbatim from Daniel. The general idea of the patch
is not very different from what Ido originally posted but instead done at the
cls_api codepath.
Fixes: 54a59aed39 ("net, sched: Make tc-related drop reason more flexible")
Reported-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/netdev/ZTjY959R+AFXf3Xy@shredder
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
40cb2fdfed