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-rw-r--r--fix_race_condition_in_packet_set_ring.diff85
1 files changed, 85 insertions, 0 deletions
diff --git a/fix_race_condition_in_packet_set_ring.diff b/fix_race_condition_in_packet_set_ring.diff
new file mode 100644
index 00000000000..25e7ca8f505
--- /dev/null
+++ b/fix_race_condition_in_packet_set_ring.diff
@@ -0,0 +1,85 @@
+From: Philip Pettersson <philip.pettersson@gmail.com>
+
+When packet_set_ring creates a ring buffer it will initialize a
+struct timer_list if the packet version is TPACKET_V3. This value
+can then be raced by a different thread calling setsockopt to
+set the version to TPACKET_V1 before packet_set_ring has finished.
+
+This leads to a use-after-free on a function pointer in the
+struct timer_list when the socket is closed as the previously
+initialized timer will not be deleted.
+
+The bug is fixed by taking lock_sock(sk) in packet_setsockopt when
+changing the packet version while also taking the lock at the start
+of packet_set_ring.
+
+Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.")
+Signed-off-by: Philip Pettersson <philip.pettersson@gmail.com>
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+---
+ net/packet/af_packet.c | 18 ++++++++++++------
+ 1 file changed, 12 insertions(+), 6 deletions(-)
+
+diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
+index d2238b204691b8e4f2e3acb9bc167b553ba32d50..dd2332390c45bbff7c3fc5d259453f2e1ca352bf 100644
+--- a/net/packet/af_packet.c
++++ b/net/packet/af_packet.c
+@@ -3648,19 +3648,25 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
+
+ if (optlen != sizeof(val))
+ return -EINVAL;
+- if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
+- return -EBUSY;
+ if (copy_from_user(&val, optval, sizeof(val)))
+ return -EFAULT;
+ switch (val) {
+ case TPACKET_V1:
+ case TPACKET_V2:
+ case TPACKET_V3:
+- po->tp_version = val;
+- return 0;
++ break;
+ default:
+ return -EINVAL;
+ }
++ lock_sock(sk);
++ if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
++ ret = -EBUSY;
++ } else {
++ po->tp_version = val;
++ ret = 0;
++ }
++ release_sock(sk);
++ return ret;
+ }
+ case PACKET_RESERVE:
+ {
+@@ -4164,6 +4170,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
+ /* Added to avoid minimal code churn */
+ struct tpacket_req *req = &req_u->req;
+
++ lock_sock(sk);
+ /* Opening a Tx-ring is NOT supported in TPACKET_V3 */
+ if (!closing && tx_ring && (po->tp_version > TPACKET_V2)) {
+ net_warn_ratelimited("Tx-ring is not supported.\n");
+@@ -4245,7 +4252,6 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
+ goto out;
+ }
+
+- lock_sock(sk);
+
+ /* Detach socket from network */
+ spin_lock(&po->bind_lock);
+@@ -4294,11 +4300,11 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
+ if (!tx_ring)
+ prb_shutdown_retire_blk_timer(po, rb_queue);
+ }
+- release_sock(sk);
+
+ if (pg_vec)
+ free_pg_vec(pg_vec, order, req->tp_block_nr);
+ out:
++ release_sock(sk);
+ return err;
+ }
+