[3.13.y.z extended stable] Patch "net: sctp: propagate sysctl errors from proc_do* properly" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    net: sctp: propagate sysctl errors from proc_do* properly

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 9b9b964c35ad3dc3da5e852ebb520776444c44cb Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman at redhat.com>
Date: Thu, 19 Jun 2014 01:31:30 +0200
Subject: 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 at redhat.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sctp/sysctl.c | 43 +++++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index b2da788..7c4eac4 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -307,41 +307,40 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl, int write,
 				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;
 	}
@@ -354,11 +353,10 @@ static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
 				loff_t *ppos)
 {
 	struct net *net = current->nsproxy->net_ns;
-	int new_value;
-	struct ctl_table tbl;
 	unsigned int min = *(unsigned int *) ctl->extra1;
 	unsigned int max = *(unsigned int *) ctl->extra2;
-	int ret;
+	struct ctl_table tbl;
+	int ret, new_value;

 	memset(&tbl, 0, sizeof(struct ctl_table));
 	tbl.maxlen = sizeof(unsigned int);
@@ -367,12 +365,15 @@ static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
 		tbl.data = &new_value;
 	else
 		tbl.data = &net->sctp.rto_min;
+
 	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
-	if (write) {
-		if (ret || new_value > max || new_value < min)
+	if (write && ret == 0) {
+		if (new_value > max || new_value < min)
 			return -EINVAL;
+
 		net->sctp.rto_min = new_value;
 	}
+
 	return ret;
 }

@@ -381,11 +382,10 @@ static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
 				loff_t *ppos)
 {
 	struct net *net = current->nsproxy->net_ns;
-	int new_value;
-	struct ctl_table tbl;
 	unsigned int min = *(unsigned int *) ctl->extra1;
 	unsigned int max = *(unsigned int *) ctl->extra2;
-	int ret;
+	struct ctl_table tbl;
+	int ret, new_value;

 	memset(&tbl, 0, sizeof(struct ctl_table));
 	tbl.maxlen = sizeof(unsigned int);
@@ -394,12 +394,15 @@ static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
 		tbl.data = &new_value;
 	else
 		tbl.data = &net->sctp.rto_max;
+
 	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
-	if (write) {
-		if (ret || new_value > max || new_value < min)
+	if (write && ret == 0) {
+		if (new_value > max || new_value < min)
 			return -EINVAL;
+
 		net->sctp.rto_max = new_value;
 	}
+
 	return ret;
 }

--
1.9.1