net: sctp: check proc_dointvec result in proc_sctp_do_auth

[ Upstream commit 24599e61b7552673dd85971cf5a35369cd8c119e ]

When writing to the sysctl field net.sctp.auth_enable, it can well
be that the user buffer we handed over to proc_dointvec() via
proc_sctp_do_auth() handler contains something other than integers.

In that case, we would set an uninitialized 4-byte value from the
stack to net->sctp.auth_enable that can be leaked back when reading
the sysctl variable, and it can unintentionally turn auth_enable
on/off based on the stack content since auth_enable is interpreted
as a boolean.

Fix it up by making sure proc_dointvec() returned sucessfully.

Fixes: b14878ccb7fa ("net: sctp: cache auth_enable per endpoint")
Reported-by: Florian Westphal <fwestpha@redhat.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index fe0ba7488bdf5f55a51392e28611ec96cd596c2b..29299dcabfbb77be13856478fb7feb667efcf854 100644 (file)
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -368,8 +368,7 @@ static int proc_sctp_do_auth(struct ctl_table *ctl, int write,
                tbl.data = &net->sctp.auth_enable;
 
        ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
-
-       if (write) {
+       if (write && ret == 0) {
                struct sock *sk = net->sctp.ctl_sock;
 
                net->sctp.auth_enable = new_value;