[PATCH net-next v2] sock: Correct error checking condition for (assign|release)_proto_idx()

[Zijun Hu]

From: Zijun Hu <quic_zijuhu@xxxxxxxxxxx>

(assign|release)_proto_idx() wrongly check find_first_zero_bit() failure
by condition '(prot->inuse_idx == PROTO_INUSE_NR - 1)' obviously.

Fix by correcting the condition to '(prot->inuse_idx == PROTO_INUSE_NR)'

Fixes: 13ff3d6fa4e6 ("[SOCK]: Enumerate struct proto-s to facilitate percpu inuse accounting (v2).")
Signed-off-by: Zijun Hu <quic_zijuhu@xxxxxxxxxxx>
---
Changes in v2:
- Remove @prot->inuse_idx checks in fastpath
- Correct tile and commit message
- Link to v1: https://lore.kernel.org/r/20250408-fix_net-v1-1-375271a79c11@xxxxxxxxxxx
---
 net/core/sock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 323892066def8ba517ff59f98f2e4ab47edd4e63..e2c3c4bd9cd915706678137d98a15ca8c1a35cb8 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3999,7 +3999,7 @@ static int assign_proto_idx(struct proto *prot)
 {
 	prot->inuse_idx = find_first_zero_bit(proto_inuse_idx, PROTO_INUSE_NR);
 
-	if (unlikely(prot->inuse_idx == PROTO_INUSE_NR - 1)) {
+	if (unlikely(prot->inuse_idx == PROTO_INUSE_NR)) {
 		pr_err("PROTO_INUSE_NR exhausted\n");
 		return -ENOSPC;
 	}
@@ -4010,7 +4010,7 @@ static int assign_proto_idx(struct proto *prot)
 
 static void release_proto_idx(struct proto *prot)
 {
-	if (prot->inuse_idx != PROTO_INUSE_NR - 1)
+	if (prot->inuse_idx != PROTO_INUSE_NR)
 		clear_bit(prot->inuse_idx, proto_inuse_idx);
 }
 #else

---
base-commit: 34a07c5b257453b5fcadc2408719c7b075844014
change-id: 20250405-fix_net-3e8364d302ff

Best regards,
-- 
Zijun Hu <quic_zijuhu@xxxxxxxxxxx>