Fixes deadlock described in this bug: https://syzkaller.appspot.com/bug?extid=e953a8f3071f5c0a28fd. Specific crash report here: https://syzkaller.appspot.com/text?tag=CrashReport&x=14670e07980000. This bug is a false positive lockdep warning since gtp and smc use completely different socket protocols. Lockdep thinks that lock_sock() in smc will deadlock with gtp's lock_sock() acquisition. Adding a function that initializes lockdep labels for smc socks resolved the false positives in lockdep upon testing. Since smc uses AF_SMC and SOCKSTREAM, two labels are created to distinguish between proper smc socks and non smc socks incorrectly input into the function. Signed-off-by: Daniel Yang <danielyangkang@xxxxxxxxx> Reported-by: syzbot+e953a8f3071f5c0a28fd@xxxxxxxxxxxxxxxxxxxxxxxxx --- v1->v2: Add lockdep annotations instead of changing locking order net/smc/af_smc.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 0316217b7..4de70bfd5 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -16,6 +16,8 @@ * based on prototype from Frank Blaschka */ +#include "linux/lockdep_types.h" +#include "linux/socket.h" #define KMSG_COMPONENT "smc" #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt @@ -2755,6 +2757,24 @@ int smc_getname(struct socket *sock, struct sockaddr *addr, return smc->clcsock->ops->getname(smc->clcsock, addr, peer); } +static struct lock_class_key smc_slock_key[2]; +static struct lock_class_key smc_key[2]; + +static inline void smc_sock_lock_init(struct sock *sk) +{ + bool is_smc = (sk->sk_family == AF_SMC) && sk_is_tcp(sk); + + sock_lock_init_class_and_name(sk, + is_smc ? + "smc_lock-AF_SMC_SOCKSTREAM" : + "smc_lock-INVALID", + &smc_slock_key[is_smc], + is_smc ? + "smc_sk_lock-AF_SMC_SOCKSTREAM" : + "smc_sk_lock-INVALID", + &smc_key[is_smc]); +} + int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) { struct sock *sk = sock->sk; @@ -2762,6 +2782,7 @@ int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) int rc; smc = smc_sk(sk); + smc_sock_lock_init(sk); lock_sock(sk); /* SMC does not support connect with fastopen */ -- 2.39.2
