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

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>

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 26d50c5..3e0fc51 100644 (file)
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -320,7 +320,7 @@ 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));