From 122d74fac84204b9a98263636f6f9a3b2e665639 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 24 Jan 2020 23:08:04 +0000 Subject: rxrpc: Fix use-after-free in rxrpc_receive_data() The subpacket scanning loop in rxrpc_receive_data() references the subpacket count in the private data part of the sk_buff in the loop termination condition. However, when the final subpacket is pasted into the ring buffer, the function is no longer has a ref on the sk_buff and should not be looking at sp->* any more. This point is actually marked in the code when skb is cleared (but sp is not - which is an error). Fix this by caching sp->nr_subpackets in a local variable and using that instead. Also clear 'sp' to catch accesses after that point. This can show up as an oops in rxrpc_get_skb() if sp->nr_subpackets gets trashed by the sk_buff getting freed and reused in the meantime. Fixes: e2de6c404898 ("rxrpc: Use info in skbuff instead of reparsing a jumbo packet") Signed-off-by: David Howells Signed-off-by: David S. Miller --- net/rxrpc/input.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'net') diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c index 86bd133b4fa0..96d54e5bf7bc 100644 --- a/net/rxrpc/input.c +++ b/net/rxrpc/input.c @@ -413,7 +413,7 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb) { struct rxrpc_skb_priv *sp = rxrpc_skb(skb); enum rxrpc_call_state state; - unsigned int j; + unsigned int j, nr_subpackets; rxrpc_serial_t serial = sp->hdr.serial, ack_serial = 0; rxrpc_seq_t seq0 = sp->hdr.seq, hard_ack; bool immediate_ack = false, jumbo_bad = false; @@ -457,7 +457,8 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb) call->ackr_prev_seq = seq0; hard_ack = READ_ONCE(call->rx_hard_ack); - if (sp->nr_subpackets > 1) { + nr_subpackets = sp->nr_subpackets; + if (nr_subpackets > 1) { if (call->nr_jumbo_bad > 3) { ack = RXRPC_ACK_NOSPACE; ack_serial = serial; @@ -465,11 +466,11 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb) } } - for (j = 0; j < sp->nr_subpackets; j++) { + for (j = 0; j < nr_subpackets; j++) { rxrpc_serial_t serial = sp->hdr.serial + j; rxrpc_seq_t seq = seq0 + j; unsigned int ix = seq & RXRPC_RXTX_BUFF_MASK; - bool terminal = (j == sp->nr_subpackets - 1); + bool terminal = (j == nr_subpackets - 1); bool last = terminal && (sp->rx_flags & RXRPC_SKB_INCL_LAST); u8 flags, annotation = j; @@ -506,7 +507,7 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb) } if (call->rxtx_buffer[ix]) { - rxrpc_input_dup_data(call, seq, sp->nr_subpackets > 1, + rxrpc_input_dup_data(call, seq, nr_subpackets > 1, &jumbo_bad); if (ack != RXRPC_ACK_DUPLICATE) { ack = RXRPC_ACK_DUPLICATE; @@ -564,6 +565,7 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb) * ring. */ skb = NULL; + sp = NULL; } if (last) { -- cgit v1.2.3-59-g8ed1b