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rxrpc: Fix local refcounting 

Fix rxrpc_unuse_local() to handle a NULL local pointer as it can be called
on an unbound socket on which rx->local is not yet set.

The following reproduced (includes omitted):

	int main(void)
	{
		socket(AF_RXRPC, SOCK_DGRAM, AF_INET);
		return 0;
	}

causes the following oops to occur:

	BUG: kernel NULL pointer dereference, address: 0000000000000010
	...
	RIP: 0010:rxrpc_unuse_local+0x8/0x1b
	...
	Call Trace:
	 rxrpc_release+0x2b5/0x338
	 __sock_release+0x37/0xa1
	 sock_close+0x14/0x17
	 __fput+0x115/0x1e9
	 task_work_run+0x72/0x98
	 do_exit+0x51b/0xa7a
	 ? __context_tracking_exit+0x4e/0x10e
	 do_group_exit+0xab/0xab
	 __x64_sys_exit_group+0x14/0x17
	 do_syscall_64+0x89/0x1d4
	 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Reported-by: syzbot+20dee719a2e090427b5f@syzkaller.appspotmail.com
Fixes: 730c5fd42c ("rxrpc: Fix local endpoint refcounting")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeffrey Altman <jaltman@auristor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Howells 2019-08-09 22:47:47 +01:00 committed by David S. Miller
parent 59c84b9fcf
commit 68553f1a6f
1 changed files with 7 additions and 5 deletions
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12
net/rxrpc/local_object.c
View File

@ -402,11 +402,13 @@ void rxrpc_unuse_local(struct rxrpc_local *local)
{
unsigned int au;
au = atomic_dec_return(&local->active_users);
if (au == 0)
rxrpc_queue_local(local);
else
rxrpc_put_local(local);
if (local) {
au = atomic_dec_return(&local->active_users);
if (au == 0)
rxrpc_queue_local(local);
else
rxrpc_put_local(local);
}
}
/*