On Sat, Oct 5, 2024 at 6:54 AM Daniel Yang <danielyangkang@xxxxxxxxx> wrote: > > 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 > sock_lock_init_class_and_name() is not meant to be repeatedly called, from sendmsg() Find a way to do this once, perhaps in smc_create_clcsk(), but I will let SMC experts chime in.
