From d0d5c0cd1e711c98703f3544c1e6fc1372898de5 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 27 Aug 2019 10:13:46 +0100 Subject: 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: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code") Reported-by: Julian Wollrath Signed-off-by: David Howells --- include/trace/events/rxrpc.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'include/trace/events/rxrpc.h') diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h index e2356c51883b..a13a62db3565 100644 --- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -32,6 +32,8 @@ enum rxrpc_skb_trace { rxrpc_skb_received, rxrpc_skb_rotated, rxrpc_skb_seen, + rxrpc_skb_unshared, + rxrpc_skb_unshared_nomem, }; enum rxrpc_local_trace { @@ -231,7 +233,9 @@ enum rxrpc_tx_point { EM(rxrpc_skb_purged, "PUR") \ EM(rxrpc_skb_received, "RCV") \ EM(rxrpc_skb_rotated, "ROT") \ - E_(rxrpc_skb_seen, "SEE") + EM(rxrpc_skb_seen, "SEE") \ + EM(rxrpc_skb_unshared, "UNS") \ + E_(rxrpc_skb_unshared_nomem, "US0") #define rxrpc_local_traces \ EM(rxrpc_local_got, "GOT") \ @@ -633,9 +637,9 @@ TRACE_EVENT(rxrpc_call, TRACE_EVENT(rxrpc_skb, TP_PROTO(struct sk_buff *skb, enum rxrpc_skb_trace op, - int usage, int mod_count, const void *where), + int usage, int mod_count, u8 flags, const void *where), - TP_ARGS(skb, op, usage, mod_count, where), + TP_ARGS(skb, op, usage, mod_count, flags, where), TP_STRUCT__entry( __field(struct sk_buff *, skb ) @@ -648,7 +652,7 @@ TRACE_EVENT(rxrpc_skb, TP_fast_assign( __entry->skb = skb; - __entry->flags = rxrpc_skb(skb)->rx_flags; + __entry->flags = flags; __entry->op = op; __entry->usage = usage; __entry->mod_count = mod_count; -- cgit v1.2.3