soreuseport: fix initialization race
Syzkaller stumbled upon a way to trigger WARNING: CPU: 1 PID: 13881 at net/core/sock_reuseport.c:41 reuseport_alloc+0x306/0x3b0 net/core/sock_reuseport.c:39 There are two initialization paths for the sock_reuseport structure in a socket: Through the udp/tcp bind paths of SO_REUSEPORT sockets or through SO_ATTACH_REUSEPORT_[CE]BPF before bind. The existing implementation assumedthat the socket lock protected both of these paths when it actually only protects the SO_ATTACH_REUSEPORT path. Syzkaller triggered this double allocation by running these paths concurrently. This patch moves the check for double allocation into the reuseport_alloc function which is protected by a global spin lock. Fixes: e32ea7e7 ("soreuseport: fast reuseport UDP socket selection") Fixes: c125e80b ("soreuseport: fast reuseport TCP socket selection") Signed-off-by: NCraig Gallek <kraig@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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