nbd: fix circular lock dependency between tx_lock and sk_lock#1018
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nbd: fix circular lock dependency between tx_lock and sk_lock#1018blktests-ci[bot] wants to merge 1 commit into
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Move kernel_sock_shutdown() out of the tx_lock critical section to break the circular lock dependency: tx_lock -> sk_lock (via inet_shutdown) vs the reverse order in the block I/O submission path. The lockdep splat shows: sk_lock-AF_INET6 --> &cmd->lock --> &nsock->tx_lock When recv_work() detects a connection failure, it calls nbd_mark_nsock_dead() under tx_lock, which calls kernel_sock_shutdown() -> inet_shutdown() -> lock_sock(), creating the tx_lock -> sk_lock dependency that conflicts with the reverse order in the I/O path. Fix this by introducing a deferred shutdown mechanism: nbd_mark_nsock_dead() records the socket needing shutdown in nsock->shutdown_sock (with an extra file reference to prevent use-after-free from the reconnect path), and the actual kernel_sock_shutdown() is performed by nbd_nsock_deferred_shutdown() after tx_lock is released at each call site. The helper uses xchg() to guarantee the shutdown is executed exactly once even when multiple paths race to consume it. Fixes: f373324 ("nbd: handle single path failures gracefully") Reported-by: syzbot+576095eed5658cbd9b63@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=576095eed5658cbd9b63 Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
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Pull request for series with
subject: nbd: fix circular lock dependency between tx_lock and sk_lock
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1117816