net: sctp: propagate sysctl errors from proc_do* properly

[ Upstream commit ff5e92c1affe7166b3f6e7073e648ed65a6e2e59 ]

sysctl handler proc_sctp_do_hmac_alg(), proc_sctp_do_rto_min() and
proc_sctp_do_rto_max() do not properly reflect some error cases
when writing values via sysctl from internal proc functions such
as proc_dointvec() and proc_dostring().

In all these cases we pass the test for write != 0 and partially
do additional work just to notice that additional sanity checks
fail and we return with hard-coded -EINVAL while proc_do*
functions might also return different errors. So fix this up by
simply testing a successful return of proc_do* right after
calling it.

This also allows to propagate its return value onwards to the user.
While touching this, also fix up some minor style issues.

Fixes: 4f3fdf3bc59c ("sctp: add check rto_min and rto_max in sysctl")
Fixes: 3c68198e7511 ("sctp: Make hmac algorithm selection for cookie generation dynamic")
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 3e5ac194860734a2a0ebff0ad5de8b4b58d86c1c..976c89d5295b409bad070ad80bac7a17880a3201 100644 (file)
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -303,41 +303,40 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl,
                                loff_t *ppos)
 {
        struct net *net = current->nsproxy->net_ns;
-       char tmp[8];
        struct ctl_table tbl;
-       int ret;
-       int changed = 0;
+       bool changed = false;
        char *none = "none";
+       char tmp[8];
+       int ret;
 
        memset(&tbl, 0, sizeof(struct ctl_table));
 
        if (write) {
                tbl.data = tmp;
-               tbl.maxlen = 8;
+               tbl.maxlen = sizeof(tmp);
        } else {
                tbl.data = net->sctp.sctp_hmac_alg ? : none;
                tbl.maxlen = strlen(tbl.data);
        }
-               ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
 
-       if (write) {
+       ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+       if (write && ret == 0) {
 #ifdef CONFIG_CRYPTO_MD5
                if (!strncmp(tmp, "md5", 3)) {
                        net->sctp.sctp_hmac_alg = "md5";
-                       changed = 1;
+                       changed = true;
                }
 #endif
 #ifdef CONFIG_CRYPTO_SHA1
                if (!strncmp(tmp, "sha1", 4)) {
                        net->sctp.sctp_hmac_alg = "sha1";
-                       changed = 1;
+                       changed = true;
                }
 #endif
                if (!strncmp(tmp, "none", 4)) {
                        net->sctp.sctp_hmac_alg = NULL;
-                       changed = 1;
+                       changed = true;
                }
-
                if (!changed)
                        ret = -EINVAL;
        }