From d6ae3bae3d1bf7a8bf367e29f2cac0788dcd0db5 Mon Sep 17 00:00:00 2001 From: Alban Crequy Date: Tue, 18 Jan 2011 06:39:15 +0000 Subject: [PATCH] af_unix: implement socket filter Linux Socket Filters can already be successfully attached and detached on unix sockets with setsockopt(sockfd, SOL_SOCKET, SO_{ATTACH,DETACH}_FILTER, ...). See: Documentation/networking/filter.txt But the filter was never used in the unix socket code so it did not work. This patch uses sk_filter() to filter buffers before delivery. This short program demonstrates the problem on SOCK_DGRAM. int main(void) { int i, j, ret; int sv[2]; struct pollfd fds[2]; char *message = "Hello world!"; char buffer[64]; struct sock_filter ins[32] = {{0,},}; struct sock_fprog filter; socketpair(AF_UNIX, SOCK_DGRAM, 0, sv); for (i = 0 ; i < 2 ; i++) { fds[i].fd = sv[i]; fds[i].events = POLLIN; fds[i].revents = 0; } for(j = 1 ; j < 13 ; j++) { /* Set a socket filter to truncate the message */ memset(ins, 0, sizeof(ins)); ins[0].code = BPF_RET|BPF_K; ins[0].k = j; filter.len = 1; filter.filter = ins; setsockopt(sv[1], SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)); /* send a message */ send(sv[0], message, strlen(message) + 1, 0); /* The filter should let the message pass but truncated. */ poll(fds, 2, 0); /* Receive the truncated message*/ ret = recv(sv[1], buffer, 64, 0); printf("received %d bytes, expected %d\n", ret, j); } for (i = 0 ; i < 2 ; i++) close(sv[i]); return 0; } Signed-off-by: Alban Crequy Reviewed-by: Ian Molton Signed-off-by: David S. Miller --- net/unix/af_unix.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index dd419d286204..8d9bbba345a4 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1475,6 +1475,12 @@ restart: goto out_free; } + if (sk_filter(other, skb) < 0) { + /* Toss the packet but do not return any error to the sender */ + err = len; + goto out_free; + } + unix_state_lock(other); err = -EPERM; if (!unix_may_send(sk, other)) -- 2.20.1