ppp, slip: Validate VJ compression slot parameters completely

Currently slhc_init() treats out-of-range values of rslots and tslots
as equivalent to 0, except that if tslots is too large it will
dereference a null pointer (CVE-2015-7799).

Add a range-check at the top of the function and make it return an
ERR_PTR() on error instead of NULL.  Change the callers accordingly.

Compile-tested only.

Reported-by: 郭永刚 <guoyonggang@360.cn>
References: http://article.gmane.org/gmane.comp.security.oss.general/17908
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 6 deletions

diff --git a/drivers/isdn/i4l/isdn_ppp.c b/drivers/isdn/i4l/isdn_ppp.c
index 86f9abebcb72..9c1e8adaf4fc 100644
--- a/drivers/isdn/i4l/isdn_ppp.c
+++ b/drivers/isdn/i4l/isdn_ppp.c
@@ -322,9 +322,9 @@ isdn_ppp_open(int min, struct file *file)
          * VJ header compression init
          */
         is->slcomp = slhc_init(16, 16); /* not necessary for 2. link in bundle */
-        if (!is->slcomp) {
+        if (IS_ERR(is->slcomp)) {
                 isdn_ppp_ccp_reset_free(is);
-                return -ENOMEM;
+                return PTR_ERR(is->slcomp);
         }
 #endif
 #ifdef CONFIG_IPPP_FILTER
@@ -573,10 +573,8 @@ isdn_ppp_ioctl(int min, struct file *file, unsigned int cmd, unsigned long arg)
                         is->maxcid = val;
 #ifdef CONFIG_ISDN_PPP_VJ
                         sltmp = slhc_init(16, val);
-                        if (!sltmp) {
-                                printk(KERN_ERR "ippp, can't realloc slhc struct\n");
-                                return -ENOMEM;
-                        }
+                        if (IS_ERR(sltmp))
+                                return PTR_ERR(sltmp);
                         if (is->slcomp)
                                 slhc_free(is->slcomp);
                         is->slcomp = sltmp;