syzbot is hitting skb_assert_len() warning at __dev_queue_xmit() [1],
for PF_IEEE802154 socket's zero-sized raw_sendmsg() request is hitting
__dev_queue_xmit() with skb->len == 0.
Since PF_IEEE802154 socket's zero-sized raw_sendmsg() request was
able to return 0, don't call __dev_queue_xmit() if packet length is 0.
----------
#include <sys/socket.h>
#include <netinet/in.h>
int main(int argc, char *argv[])
{
struct sockaddr_in addr = { .sin_family = AF_INET, .sin_addr.s_addr = htonl(INADDR_LOOPBACK) };
struct iovec iov = { };
struct msghdr hdr = { .msg_name = &addr, .msg_namelen = sizeof(addr), .msg_iov = &iov, .msg_iovlen = 1 };
sendmsg(socket(PF_IEEE802154, SOCK_RAW, 0), &hdr, 0);
return 0;
}
----------
Note that this might be a sign that commit fd1894224407c484 ("bpf: Don't
redirect packets with invalid pkt_len") should be reverted, for
skb->len == 0 was acceptable for at least PF_IEEE802154 socket.
Link: https://syzkaller.appspot.com/bug?extid=5ea725c25d06fb9114c4 [1]
Reported-by: syzbot <syzbot+5ea725c25d06fb9114c4@xxxxxxxxxxxxxxxxxxxxxxxxx>
Fixes: fd1894224407c484 ("bpf: Don't redirect packets with invalid pkt_len")
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
Changes in v2:
Return 0 after checking -ENXIO case, for a test program shown above
returns -ENXIO if dev was not found and returns 0 otherwise.
net/ieee802154/socket.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/ieee802154/socket.c b/net/ieee802154/socket.c
index 7889e1ef7fad..6e55fae4c686 100644
--- a/net/ieee802154/socket.c
+++ b/net/ieee802154/socket.c
@@ -272,6 +272,10 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
err = -EMSGSIZE;
goto out_dev;
}
+ if (!size) {
+ err = 0;
+ goto out_dev;
+ }
hlen = LL_RESERVED_SPACE(dev);
tlen = dev->needed_tailroom;
--
2.34.1
