From: David Howells dhowells@redhat.com
commit 55f6c98e3674ce16038a1949c3f9ca5a9a99f289 upstream.
rxrpc_put_peer() calls trace_rxrpc_peer() after it has done the decrement of the refcount - which looks at the debug_id in the peer record. But unless the refcount was reduced to zero, we no longer have the right to look in the record and, indeed, it may be deleted by some other thread.
Fix this by getting the debug_id out before decrementing the refcount and then passing that into the tracepoint.
This can cause the following symptoms:
BUG: KASAN: use-after-free in __rxrpc_put_peer net/rxrpc/peer_object.c:411 [inline] BUG: KASAN: use-after-free in rxrpc_put_peer+0x685/0x6a0 net/rxrpc/peer_object.c:435 Read of size 8 at addr ffff888097ec0058 by task syz-executor823/24216
Fixes: 1159d4b496f5 ("rxrpc: Add a tracepoint to track rxrpc_peer refcounting") Reported-by: syzbot+b9be979c55f2bea8ed30@syzkaller.appspotmail.com Signed-off-by: David Howells dhowells@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/trace/events/rxrpc.h | 6 +++--- net/rxrpc/peer_object.c | 11 +++++++---- 2 files changed, 10 insertions(+), 7 deletions(-)
--- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -527,10 +527,10 @@ TRACE_EVENT(rxrpc_local, );
TRACE_EVENT(rxrpc_peer, - TP_PROTO(struct rxrpc_peer *peer, enum rxrpc_peer_trace op, + TP_PROTO(unsigned int peer_debug_id, enum rxrpc_peer_trace op, int usage, const void *where),
- TP_ARGS(peer, op, usage, where), + TP_ARGS(peer_debug_id, op, usage, where),
TP_STRUCT__entry( __field(unsigned int, peer ) @@ -540,7 +540,7 @@ TRACE_EVENT(rxrpc_peer, ),
TP_fast_assign( - __entry->peer = peer->debug_id; + __entry->peer = peer_debug_id; __entry->op = op; __entry->usage = usage; __entry->where = where; --- a/net/rxrpc/peer_object.c +++ b/net/rxrpc/peer_object.c @@ -385,7 +385,7 @@ struct rxrpc_peer *rxrpc_get_peer(struct int n;
n = atomic_inc_return(&peer->usage); - trace_rxrpc_peer(peer, rxrpc_peer_got, n, here); + trace_rxrpc_peer(peer->debug_id, rxrpc_peer_got, n, here); return peer; }
@@ -399,7 +399,7 @@ struct rxrpc_peer *rxrpc_get_peer_maybe( if (peer) { int n = atomic_fetch_add_unless(&peer->usage, 1, 0); if (n > 0) - trace_rxrpc_peer(peer, rxrpc_peer_got, n + 1, here); + trace_rxrpc_peer(peer->debug_id, rxrpc_peer_got, n + 1, here); else peer = NULL; } @@ -430,11 +430,13 @@ static void __rxrpc_put_peer(struct rxrp void rxrpc_put_peer(struct rxrpc_peer *peer) { const void *here = __builtin_return_address(0); + unsigned int debug_id; int n;
if (peer) { + debug_id = peer->debug_id; n = atomic_dec_return(&peer->usage); - trace_rxrpc_peer(peer, rxrpc_peer_put, n, here); + trace_rxrpc_peer(debug_id, rxrpc_peer_put, n, here); if (n == 0) __rxrpc_put_peer(peer); } @@ -447,10 +449,11 @@ void rxrpc_put_peer(struct rxrpc_peer *p void rxrpc_put_peer_locked(struct rxrpc_peer *peer) { const void *here = __builtin_return_address(0); + unsigned int debug_id = peer->debug_id; int n;
n = atomic_dec_return(&peer->usage); - trace_rxrpc_peer(peer, rxrpc_peer_put, n, here); + trace_rxrpc_peer(debug_id, rxrpc_peer_put, n, here); if (n == 0) { hash_del_rcu(&peer->hash_link); list_del_init(&peer->keepalive_link);