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

[ Upstream commit 320f1a4a175e7cd5d3f006f92b4d4d3e2cbb7bb5 ]

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: Sasha Levin <sasha.levin@oracle.com>

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 2e9ada10fd846c10bc6281c30f29cf1fed02ca3c..5b6e7571081cbe7a3ac143cd3c250fdeb4364b35 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));