diff mbox series

rxrpc_find_service_conn_rcu: fix the usage of read_seqbegin_or_lock()

Message ID 20231117164846.GA10410@redhat.com (mailing list archive)
State Awaiting Upstream
Delegated to: Netdev Maintainers
Headers show
Series rxrpc_find_service_conn_rcu: fix the usage of read_seqbegin_or_lock() | expand

Checks

Context Check Description
netdev/series_format warning Single patches do not need cover letters; Target tree name not specified in the subject
netdev/tree_selection success Guessed tree name to be net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1129 this patch: 1129
netdev/cc_maintainers warning 5 maintainers not CCed: marc.dionne@auristor.com linux-afs@lists.infradead.org pabeni@redhat.com edumazet@google.com kuba@kernel.org
netdev/build_clang success Errors and warnings before: 1154 this patch: 1154
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1156 this patch: 1156
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 15 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Oleg Nesterov Nov. 17, 2023, 4:48 p.m. UTC 
rxrpc_find_service_conn_rcu() should make the "seq" counter odd on the
second pass, otherwise read_seqbegin_or_lock() never takes the lock.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 net/rxrpc/conn_service.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/net/rxrpc/conn_service.c b/net/rxrpc/conn_service.c
index 89ac05a711a4..39c908a3ca6e 100644
--- a/net/rxrpc/conn_service.c
+++ b/net/rxrpc/conn_service.c
@@ -25,7 +25,7 @@  struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
 	struct rxrpc_conn_proto k;
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct rb_node *p;
-	unsigned int seq = 0;
+	unsigned int seq = 1;
 
 	k.epoch	= sp->hdr.epoch;
 	k.cid	= sp->hdr.cid & RXRPC_CIDMASK;
@@ -35,6 +35,7 @@  struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
 		 * under just the RCU read lock, so we have to check for
 		 * changes.
 		 */
+		seq++; /* 2 on the 1st/lockless path, otherwise odd */
 		read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
 
 		p = rcu_dereference_raw(peer->service_conns.rb_node);