net: sctp: prevent writes to cookie_hmac_alg from accessing invalid memory

commit 320f1a4a175e7cd5d3f006f92b4d4d3e2cbb7bb5 upstream.

proc_dostring() needs an initialized destination string, while the one
provided in proc_sctp_do_hmac_alg() contains stack garbage.

Thus, writing to cookie_hmac_alg would strlen() that garbage and end up
accessing invalid memory.

Fixes: 3c68198e7 ("sctp: Make hmac algorithm selection for cookie generation dynamic")
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 12c7e01c267711ef19878f6c1da1e66e257ecf7e..0b8583647355a36e7796f1f5841c8836063760a5 100644 (file)
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -324,7 +324,7 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl, int write,
        struct ctl_table tbl;
        bool changed = false;
        char *none = "none";
-       char tmp[8];
+       char tmp[8] = {0};
        int ret;
 
        memset(&tbl, 0, sizeof(struct ctl_table));