Re: crypto: deadlock between crypto_alg_sem/rtnl_mutex/genl_mutex

On Sun, Mar 05, 2017 at 04:08:39PM +0100, Dmitry Vyukov wrote:

-> #1 (genl_mutex){+.+.+.}:
       validate_chain kernel/locking/lockdep.c:2267 [inline]
       __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
       lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
       genl_lock net/netlink/genetlink.c:32 [inline]
       genl_lock_dumpit+0x41/0x90 net/netlink/genetlink.c:478
       netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
       __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
       genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
       genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
       netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
       netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
       netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
       netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
       sock_sendmsg_nosec net/socket.c:633 [inline]
       sock_sendmsg+0xca/0x110 net/socket.c:643
       sock_write_iter+0x326/0x600 net/socket.c:846
       call_write_iter include/linux/fs.h:1733 [inline]
       new_sync_write fs/read_write.c:497 [inline]
       __vfs_write+0x483/0x740 fs/read_write.c:510
       vfs_write+0x187/0x530 fs/read_write.c:558
       SYSC_write fs/read_write.c:605 [inline]
       SyS_write+0xfb/0x230 fs/read_write.c:597
       entry_SYSCALL_64_fastpath+0x1f/0xc2

-> #0 (nlk->cb_mutex){+.+.+.}:
       check_prev_add kernel/locking/lockdep.c:1830 [inline]
       check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
       validate_chain kernel/locking/lockdep.c:2267 [inline]
       __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
       lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
       __netlink_dump_start+0xf4/0x760 net/netlink/af_netlink.c:2187
       netlink_dump_start include/linux/netlink.h:165 [inline]
       crypto_user_rcv_msg+0x2ad/0x4f0 crypto/crypto_user.c:517
       netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
       crypto_netlink_rcv+0x2a/0x40 crypto/crypto_user.c:538
       netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
       netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
       netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
       sock_sendmsg_nosec net/socket.c:633 [inline]
       sock_sendmsg+0xca/0x110 net/socket.c:643
       ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
       __sys_sendmsg+0x138/0x300 net/socket.c:2019
       SYSC_sendmsg net/socket.c:2030 [inline]
       SyS_sendmsg+0x2d/0x50 net/socket.c:2026
       entry_SYSCALL_64_fastpath+0x1f/0xc2

This looks like a false positive.  The cb_mutex in #1 is not the
same as the cb_mutex in #0.  The cb_mutex in #0 comes is obtained
by crypto_user which uses straight netlink.  The cb_mutex in #1
is a genl netlink socket.

I'll have a look to see if we can annotate this.

Cheers,
-- 
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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