net: rds: fix memory leak in rds_recvmsg

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net: rds: fix memory leak in rds_recvmsg Syzbot reported memory leak in rds. The problem was in unputted refcount in case of error. int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, int msg_flags) { ... if (!rds_next_incoming(rs, &inc)) { ... } After this "if" inc refcount incremented and if (rds_cmsg_recv(inc, msg, rs)) { ret = -EFAULT; goto out; } ... out: return ret; } in case of rds_cmsg_recv() fail the refcount won't be decremented. And it's easy to see from ftrace log, that rds_inc_addref() don't have rds_inc_put() pair in rds_recvmsg() after rds_cmsg_recv() 1) | rds_recvmsg() { 1) 3.721 us | rds_inc_addref(); 1) 3.853 us | rds_message_inc_copy_to_user(); 1) + 10.395 us | rds_cmsg_recv(); 1) + 34.260 us | }

References

• https://git.kernel.org/stable/c/8c3ec88b03e9e4ca117dcdc4204fd3edcd02084f
• https://git.kernel.org/stable/c/423c6939758fb3b9cf5abbd1e7792068a5c4ae8c
• https://git.kernel.org/stable/c/1f79bc8ae81c05eb112a53f981cb2c244ee50d02
• https://git.kernel.org/stable/c/06b7cb0194bd1ede0dd27f3a946e7c0279fba44a
• https://git.kernel.org/stable/c/2038cd15eacdf7512755c27686822e0052eb9042
• https://git.kernel.org/stable/c/5946fbf48355f5a8caeff72580c7658da5966b86
• https://git.kernel.org/stable/c/b25b60d076164edb3025e85aabd2cf50a5215b91
• https://git.kernel.org/stable/c/49bfcbfd989a8f1f23e705759a6bb099de2cff9f