[PATCH 3.15 037/109] net: sctp: propagate sysctl errors from proc_do* properly

Greg Kroah-Hartman
2014-07-26T19:01:59Z

From: Daniel Borkmann <dborkman@redhat.com>

[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/sysctl.c | 43 +++++++++++++++++++++++--------------------
1 file changed, 23 insertions(+), 20 deletions(-)

--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -307,41 +307,40 @@ static int proc_sctp_do_hmac_alg(struct
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 c
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 c
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 c
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 c
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;
}