Messages in this thread | | | Date | Thu, 11 Nov 2021 15:00:02 +0100 | From | Vincent Whitchurch <> | Subject | Re: [PATCH bpf v1] unix: fix an issue in unix_shutdown causing the other end read/write failures |
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On Mon, Oct 04, 2021 at 11:25:28PM +0000, Jiang Wang wrote: > Commit 94531cfcbe79 ("af_unix: Add unix_stream_proto for sockmap") > sets unix domain socket peer state to TCP_CLOSE > in unix_shutdown. This could happen when the local end is shutdown > but the other end is not. Then the other end will get read or write > failures which is not expected. > > Fix the issue by setting the local state to shutdown. > > Fixes: 94531cfcbe79 (af_unix: Add unix_stream_proto for sockmap) > Suggested-by: Cong Wang <cong.wang@bytedance.com> > Reported-by: Casey Schaufler <casey@schaufler-ca.com> > Signed-off-by: Jiang Wang <jiang.wang@bytedance.com>
This patch changed the behaviour of read(2) after a shutdown(2) on the local end of a UDS. Before this patch, reading from a UDS after a local shutdown(SHUT_RDWR) would return the data written or EOF if there is no data, but now it always returns -EINVAL.
For example, the following test program succeeds with "read 16 bytes" on v5.14 but fails with "read: Invalid argument" on v5.15 and mainline:
#include <err.h> #include <errno.h> #include <stdio.h> #include <sys/socket.h> #include <sys/unistd.h>
int main(int argc, char *argv[]) { int sock[2]; int ret;
ret = socketpair(AF_UNIX, SOCK_STREAM, 0, sock); if (ret < 0) err(1, "socketpair");
char buf[16] = {}; ret = write(sock[1], buf, sizeof(buf)); if (ret < 0) err(1, "write");
ret = shutdown(sock[0], SHUT_RDWR); if (ret < 0) err(1, "shutdown");
ssize_t bytes = read(sock[0], buf, sizeof(buf)); if (bytes < 0) err(1, "read");
printf("read %zd bytes\n", bytes);
return 0; }
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