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rxrpc: Use skb_unshare() rather than skb_cow_data()
The in-place decryption routines in AF_RXRPC's rxkad security module
currently call skb_cow_data() to make sure the data isn't shared and that
the skb can be written over. This has a problem, however, as the softirq
handler may be still holding a ref or the Rx ring may be holding multiple
refs when skb_cow_data() is called in rxkad_verify_packet() - and so
skb_shared() returns true and __pskb_pull_tail() dislikes that. If this
occurs, something like the following report will be generated.
kernel BUG at net/core/skbuff.c:1463!
...
RIP: 0010:pskb_expand_head+0x253/0x2b0
...
Call Trace:
__pskb_pull_tail+0x49/0x460
skb_cow_data+0x6f/0x300
rxkad_verify_packet+0x18b/0xb10 [rxrpc]
rxrpc_recvmsg_data.isra.11+0x4a8/0xa10 [rxrpc]
rxrpc_kernel_recv_data+0x126/0x240 [rxrpc]
afs_extract_data+0x51/0x2d0 [kafs]
afs_deliver_fs_fetch_data+0x188/0x400 [kafs]
afs_deliver_to_call+0xac/0x430 [kafs]
afs_wait_for_call_to_complete+0x22f/0x3d0 [kafs]
afs_make_call+0x282/0x3f0 [kafs]
afs_fs_fetch_data+0x164/0x300 [kafs]
afs_fetch_data+0x54/0x130 [kafs]
afs_readpages+0x20d/0x340 [kafs]
read_pages+0x66/0x180
__do_page_cache_readahead+0x188/0x1a0
ondemand_readahead+0x17d/0x2e0
generic_file_read_iter+0x740/0xc10
__vfs_read+0x145/0x1a0
vfs_read+0x8c/0x140
ksys_read+0x4a/0xb0
do_syscall_64+0x43/0xf0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fix this by using skb_unshare() instead in the input path for DATA packets
that have a security index != 0. Non-DATA packets don't need in-place
encryption and neither do unencrypted DATA packets.
Fixes: 248f219cb8 ("rxrpc: Rewrite the data and ack handling code")
Reported-by: Julian Wollrath <jwollrath@web.de>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells
parent
987db9f7cd
commit
d0d5c0cd1e
@ -32,6 +32,8 @@ enum rxrpc_skb_trace {
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rxrpc_skb_received,
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rxrpc_skb_rotated,
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rxrpc_skb_seen,
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rxrpc_skb_unshared,
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rxrpc_skb_unshared_nomem,
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};
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enum rxrpc_local_trace {
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@ -231,7 +233,9 @@ enum rxrpc_tx_point {
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EM(rxrpc_skb_purged, "PUR") \
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EM(rxrpc_skb_received, "RCV") \
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EM(rxrpc_skb_rotated, "ROT") \
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E_(rxrpc_skb_seen, "SEE")
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EM(rxrpc_skb_seen, "SEE") \
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EM(rxrpc_skb_unshared, "UNS") \
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E_(rxrpc_skb_unshared_nomem, "US0")
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#define rxrpc_local_traces \
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EM(rxrpc_local_got, "GOT") \
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@ -633,9 +637,9 @@ TRACE_EVENT(rxrpc_call,
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TRACE_EVENT(rxrpc_skb,
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TP_PROTO(struct sk_buff *skb, enum rxrpc_skb_trace op,
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int usage, int mod_count, const void *where),
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int usage, int mod_count, u8 flags, const void *where),
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TP_ARGS(skb, op, usage, mod_count, where),
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TP_ARGS(skb, op, usage, mod_count, flags, where),
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TP_STRUCT__entry(
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__field(struct sk_buff *, skb )
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@ -648,7 +652,7 @@ TRACE_EVENT(rxrpc_skb,
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TP_fast_assign(
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__entry->skb = skb;
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__entry->flags = rxrpc_skb(skb)->rx_flags;
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__entry->flags = flags;
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__entry->op = op;
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__entry->usage = usage;
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__entry->mod_count = mod_count;
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@ -1110,6 +1110,7 @@ void rxrpc_kernel_data_consumed(struct rxrpc_call *, struct sk_buff *);
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void rxrpc_packet_destructor(struct sk_buff *);
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void rxrpc_new_skb(struct sk_buff *, enum rxrpc_skb_trace);
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void rxrpc_see_skb(struct sk_buff *, enum rxrpc_skb_trace);
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void rxrpc_eaten_skb(struct sk_buff *, enum rxrpc_skb_trace);
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void rxrpc_get_skb(struct sk_buff *, enum rxrpc_skb_trace);
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void rxrpc_free_skb(struct sk_buff *, enum rxrpc_skb_trace);
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void rxrpc_purge_queue(struct sk_buff_head *);
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@ -1249,6 +1249,24 @@ int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb)
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goto bad_message;
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if (!rxrpc_validate_data(skb))
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goto bad_message;
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/* Unshare the packet so that it can be modified for in-place
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* decryption.
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*/
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if (sp->hdr.securityIndex != 0) {
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struct sk_buff *nskb = skb_unshare(skb, GFP_ATOMIC);
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if (!nskb) {
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rxrpc_eaten_skb(skb, rxrpc_skb_unshared_nomem);
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goto out;
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}
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if (nskb != skb) {
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rxrpc_eaten_skb(skb, rxrpc_skb_received);
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rxrpc_new_skb(skb, rxrpc_skb_unshared);
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skb = nskb;
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sp = rxrpc_skb(skb);
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}
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}
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break;
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case RXRPC_PACKET_TYPE_CHALLENGE:
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@ -187,10 +187,8 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
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struct rxrpc_skb_priv *sp;
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struct rxrpc_crypt iv;
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struct scatterlist sg[16];
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struct sk_buff *trailer;
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unsigned int len;
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u16 check;
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int nsg;
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int err;
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sp = rxrpc_skb(skb);
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@ -214,15 +212,14 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
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crypto_skcipher_encrypt(req);
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/* we want to encrypt the skbuff in-place */
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nsg = skb_cow_data(skb, 0, &trailer);
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err = -ENOMEM;
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if (nsg < 0 || nsg > 16)
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err = -EMSGSIZE;
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if (skb_shinfo(skb)->nr_frags > 16)
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goto out;
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len = data_size + call->conn->size_align - 1;
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len &= ~(call->conn->size_align - 1);
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sg_init_table(sg, nsg);
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sg_init_table(sg, ARRAY_SIZE(sg));
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err = skb_to_sgvec(skb, sg, 0, len);
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if (unlikely(err < 0))
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goto out;
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@ -319,11 +316,10 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
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struct rxkad_level1_hdr sechdr;
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struct rxrpc_crypt iv;
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struct scatterlist sg[16];
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struct sk_buff *trailer;
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bool aborted;
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u32 data_size, buf;
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u16 check;
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int nsg, ret;
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int ret;
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_enter("");
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@ -336,11 +332,7 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
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/* Decrypt the skbuff in-place. TODO: We really want to decrypt
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* directly into the target buffer.
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*/
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nsg = skb_cow_data(skb, 0, &trailer);
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if (nsg < 0 || nsg > 16)
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goto nomem;
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sg_init_table(sg, nsg);
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sg_init_table(sg, ARRAY_SIZE(sg));
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ret = skb_to_sgvec(skb, sg, offset, 8);
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if (unlikely(ret < 0))
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return ret;
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@ -388,10 +380,6 @@ protocol_error:
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if (aborted)
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rxrpc_send_abort_packet(call);
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return -EPROTO;
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nomem:
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_leave(" = -ENOMEM");
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return -ENOMEM;
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}
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/*
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@ -406,7 +394,6 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
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struct rxkad_level2_hdr sechdr;
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struct rxrpc_crypt iv;
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struct scatterlist _sg[4], *sg;
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struct sk_buff *trailer;
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bool aborted;
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u32 data_size, buf;
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u16 check;
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@ -423,12 +410,11 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
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/* Decrypt the skbuff in-place. TODO: We really want to decrypt
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* directly into the target buffer.
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*/
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nsg = skb_cow_data(skb, 0, &trailer);
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if (nsg < 0)
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goto nomem;
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sg = _sg;
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if (unlikely(nsg > 4)) {
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nsg = skb_shinfo(skb)->nr_frags;
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if (nsg <= 4) {
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nsg = 4;
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} else {
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sg = kmalloc_array(nsg, sizeof(*sg), GFP_NOIO);
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if (!sg)
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goto nomem;
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@ -24,7 +24,8 @@ void rxrpc_new_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
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{
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const void *here = __builtin_return_address(0);
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int n = atomic_inc_return(select_skb_count(skb));
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n,
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rxrpc_skb(skb)->rx_flags, here);
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}
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/*
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@ -35,7 +36,8 @@ void rxrpc_see_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
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const void *here = __builtin_return_address(0);
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if (skb) {
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int n = atomic_read(select_skb_count(skb));
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n,
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rxrpc_skb(skb)->rx_flags, here);
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}
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}
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@ -46,10 +48,21 @@ void rxrpc_get_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
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{
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const void *here = __builtin_return_address(0);
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int n = atomic_inc_return(select_skb_count(skb));
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n,
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rxrpc_skb(skb)->rx_flags, here);
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skb_get(skb);
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}
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/*
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* Note the dropping of a ref on a socket buffer by the core.
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*/
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void rxrpc_eaten_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
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{
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const void *here = __builtin_return_address(0);
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int n = atomic_inc_return(&rxrpc_n_rx_skbs);
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trace_rxrpc_skb(skb, op, 0, n, 0, here);
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}
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/*
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* Note the destruction of a socket buffer.
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*/
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@ -60,7 +73,8 @@ void rxrpc_free_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
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int n;
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CHECK_SLAB_OKAY(&skb->users);
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n = atomic_dec_return(select_skb_count(skb));
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
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trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n,
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rxrpc_skb(skb)->rx_flags, here);
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kfree_skb(skb);
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}
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}
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@ -75,7 +89,8 @@ void rxrpc_purge_queue(struct sk_buff_head *list)
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while ((skb = skb_dequeue((list))) != NULL) {
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int n = atomic_dec_return(select_skb_count(skb));
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trace_rxrpc_skb(skb, rxrpc_skb_purged,
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refcount_read(&skb->users), n, here);
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refcount_read(&skb->users), n,
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rxrpc_skb(skb)->rx_flags, here);
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kfree_skb(skb);
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}
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}
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