From: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
commit dc34ebd5c018b0edf47f39d11083ad8312733034 upstream.
syzbot reports a memory leak in pppoe_sendmsg [1].
The problem is in the pppoe_recvmsg() function that handles errors
in the wrong order. For the skb_recv_datagram() function, check
the pointer to skb for NULL first, and then check the 'error' variable,
because the skb_recv_datagram() function can set 'error'
to -EAGAIN in a loop but return a correct pointer to socket buffer
after a number of attempts, though 'error' remains set to -EAGAIN.
skb_recv_datagram
__skb_recv_datagram // Loop. if (err == -EAGAIN) then
// go to the next loop iteration
__skb_try_recv_datagram // if (skb != NULL) then return 'skb'
// else if a signal is received then
// return -EAGAIN
Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with Syzkaller.
Link: https://syzkaller.appspot.com/bug?extid=6bdfd184eac7709e5cc9 [1]
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+6bdfd184eac7709e5cc9@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=6bdfd184eac7709e5cc9
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
Reviewed-by: Guillaume Nault <gnault@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240214085814.3894917-1-Ilia.Gavrilov@xxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
---
drivers/net/ppp/pppoe.c | 23 +++++++++--------------
1 file changed, 9 insertions(+), 14 deletions(-)
diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index ba8b6bd8233c..96cca4ee470a 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -1007,26 +1007,21 @@ static int pppoe_recvmsg(struct socket *sock, struct msghdr *m,
struct sk_buff *skb;
int error = 0;
- if (sk->sk_state & PPPOX_BOUND) {
- error = -EIO;
- goto end;
- }
+ if (sk->sk_state & PPPOX_BOUND)
+ return -EIO;
skb = skb_recv_datagram(sk, flags, &error);
- if (error < 0)
- goto end;
+ if (!skb)
+ return error;
- if (skb) {
- total_len = min_t(size_t, total_len, skb->len);
- error = skb_copy_datagram_msg(skb, 0, m, total_len);
- if (error == 0) {
- consume_skb(skb);
- return total_len;
- }
+ total_len = min_t(size_t, total_len, skb->len);
+ error = skb_copy_datagram_msg(skb, 0, m, total_len);
+ if (error == 0) {
+ consume_skb(skb);
+ return total_len;
}
kfree_skb(skb);
-end:
return error;
}
--
2.39.2
