ppp, slip: Validate VJ compression slot parameters completely

commit 4ab42d78e37a294ac7bc56901d563c642e03c4ae upstream.

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>
[bwh: Backported to 3.2: adjust indentation]

diff --git a/drivers/isdn/i4l/isdn_ppp.c b/drivers/isdn/i4l/isdn_ppp.c
index 0033bca..3604aa7 100644 (file)
--- 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
@@ -574,10 +574,8 @@ 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;

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 4782d79..82d4421 100644 (file)
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -703,10 +703,8 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                        val &= 0xffff;
                }
                vj = slhc_init(val2+1, val+1);
-               if (!vj) {
-                       netdev_err(ppp->dev,
-                                  "PPP: no memory (VJ compressor)\n");
-                       err = -ENOMEM;
+               if (IS_ERR(vj)) {
+                       err = PTR_ERR(vj);
                        break;
                }
                ppp_lock(ppp);

diff --git a/drivers/net/slip/slhc.c b/drivers/net/slip/slhc.c
index 0a0a664..042425e 100644 (file)
--- a/drivers/net/slip/slhc.c
+++ b/drivers/net/slip/slhc.c
@@ -85,8 +85,9 @@ static long decode(unsigned char **cpp);
 static unsigned char * put16(unsigned char *cp, unsigned short x);
 static unsigned short pull16(unsigned char **cpp);
 
-/* Initialize compression data structure
+/* Allocate compression data structure
  *     slots must be in range 0 to 255 (zero meaning no compression)
+ * Returns pointer to structure or ERR_PTR() on error.
  */
 struct slcompress *
 slhc_init(int rslots, int tslots)
@@ -95,11 +96,14 @@ slhc_init(int rslots, int tslots)
        register struct cstate *ts;
        struct slcompress *comp;
 
+       if (rslots < 0 || rslots > 255 || tslots < 0 || tslots > 255)
+               return ERR_PTR(-EINVAL);
+
        comp = kzalloc(sizeof(struct slcompress), GFP_KERNEL);
        if (! comp)
                goto out_fail;
 
-       if ( rslots > 0  &&  rslots < 256 ) {
+       if (rslots > 0) {
                size_t rsize = rslots * sizeof(struct cstate);
                comp->rstate = kzalloc(rsize, GFP_KERNEL);
                if (! comp->rstate)
@@ -107,7 +111,7 @@ slhc_init(int rslots, int tslots)
                comp->rslot_limit = rslots - 1;
        }
 
-       if ( tslots > 0  &&  tslots < 256 ) {
+       if (tslots > 0) {
                size_t tsize = tslots * sizeof(struct cstate);
                comp->tstate = kzalloc(tsize, GFP_KERNEL);
                if (! comp->tstate)
@@ -142,7 +146,7 @@ out_free2:
 out_free:
        kfree(comp);
 out_fail:
-       return NULL;
+       return ERR_PTR(-ENOMEM);
 }
 
 

diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
index ba08341..1a6e2ea 100644 (file)
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -164,7 +164,7 @@ static int sl_alloc_bufs(struct slip *sl, int mtu)
        if (cbuff == NULL)
                goto err_exit;
        slcomp = slhc_init(16, 16);
-       if (slcomp == NULL)
+       if (IS_ERR(slcomp))
                goto err_exit;
 #endif
        spin_lock_bh(&sl->lock);