The cause of the resultant dump_stack() reported below is a
dereference of a freed pointer to 'struct sctp_endpoint' in
sctp_sock_dump().
This race condition occurs when a transport is cached into its
associated hash table followed by an endpoint/sock migration to a new
association in sctp_assoc_migrate() prior to their subsequent use in
sctp_diag_dump() which uses sctp_for_each_transport() to walk the hash
table calling into sctp_sock_dump() where the dereference occurs.
BUG: KASAN: use-after-free in sctp_sock_dump+0xa8/0x438 [sctp_diag]
Call trace:
dump_backtrace+0x0/0x2dc
show_stack+0x20/0x2c
dump_stack+0x120/0x144
print_address_description+0x80/0x2f4
__kasan_report+0x174/0x194
kasan_report+0x10/0x18
__asan_load8+0x84/0x8c
sctp_sock_dump+0xa8/0x438 [sctp_diag]
sctp_for_each_transport+0x1e0/0x26c [sctp]
sctp_diag_dump+0x180/0x1f0 [sctp_diag]
inet_diag_dump+0x12c/0x168
netlink_dump+0x24c/0x5b8
__netlink_dump_start+0x274/0x2a8
inet_diag_handler_cmd+0x224/0x274
sock_diag_rcv_msg+0x21c/0x230
netlink_rcv_skb+0xe0/0x1bc
sock_diag_rcv+0x34/0x48
netlink_unicast+0x3b4/0x430
netlink_sendmsg+0x4f0/0x574
sock_write_iter+0x18c/0x1f0
do_iter_readv_writev+0x230/0x2a8
do_iter_write+0xc8/0x2b4
vfs_writev+0xf8/0x184
do_writev+0xb0/0x1a8
__arm64_sys_writev+0x4c/0x5c
el0_svc_common+0x118/0x250
el0_svc_handler+0x3c/0x9c
el0_svc+0x8/0xc
To prevent this from happening we need to take a reference to the
to-be-used/dereferenced 'struct sctp_endpoint' (which inherently
holds a reference to the problematic 'struct sock') until such a time
when we know they can be safely released.
When KASAN is not enabled, a similar, but slightly different NULL
pointer derefernce crash occurs later along the thread of execution.
This time in inet_sctp_diag_fill().
Cc: Vlad Yasevich <vyasevich@xxxxxxxxx>
Cc: Neil Horman <nhorman@xxxxxxxxxxxxx>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: lksctp developers <linux-sctp@xxxxxxxxxxxxxxx>
Cc: "H.P. Yarroll" <piggy@xxxxxxx>
Cc: Karl Knutson <karl@xxxxxxxxxxxxxxxxxxxx>
Cc: Jon Grimm <jgrimm@xxxxxxxxxx>
Cc: Xingang Guo <xingang.guo@xxxxxxxxx>
Cc: Hui Huang <hui.huang@xxxxxxxxx>
Cc: Sridhar Samudrala <sri@xxxxxxxxxx>
Cc: Daisy Chang <daisyc@xxxxxxxxxx>
Cc: Ryan Layer <rmlayer@xxxxxxxxxx>
Cc: Kevin Gao <kevin.gao@xxxxxxxxx>
Cc: linux-sctp@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 8f840e47f190c ("sctp: add the sctp_diag.c file")
Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
---
net/sctp/diag.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/sctp/diag.c b/net/sctp/diag.c
index 760b367644c12..998488a56ce2b 100644
--- a/net/sctp/diag.c
+++ b/net/sctp/diag.c
@@ -292,15 +292,17 @@ static int sctp_tsp_dump_one(struct sctp_transport *tsp, void *p)
static int sctp_sock_dump(struct sctp_transport *tsp, void *p)
{
- struct sctp_endpoint *ep = tsp->asoc->ep;
+ struct sctp_endpoint *ep;
struct sctp_comm_param *commp = p;
- struct sock *sk = ep->base.sk;
+ struct sock *sk;
struct sk_buff *skb = commp->skb;
struct netlink_callback *cb = commp->cb;
const struct inet_diag_req_v2 *r = commp->r;
struct sctp_association *assoc;
int err = 0;
+ ep = sctp_endpoint_hold(tsp->asoc->ep);
+ sk = ep->base.sk;
lock_sock(sk);
list_for_each_entry(assoc, &ep->asocs, asocs) {
if (cb->args[4] < cb->args[1])
@@ -341,6 +343,7 @@ static int sctp_sock_dump(struct sctp_transport *tsp, void *p)
cb->args[4] = 0;
release:
release_sock(sk);
+ sctp_endpoint_put(ep);
return err;
}
--
2.34.1.173.g76aa8bc2d0-goog
