From a8bc90052f18348718412cebf7b569da95bad264 Mon Sep 17 00:00:00 2001

From: Ben Hutchings <ben@decadent.org.uk>

Date: Sun, 1 Nov 2015 16:22:53 +0000

Subject: [PATCH 2/2] ppp, slip: Validate VJ compression slot parameters

 completely

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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>

---

 drivers/isdn/i4l/isdn_ppp.c   | 10 ++++------

 drivers/net/ppp/ppp_generic.c |  6 ++----

 drivers/net/slip/slhc.c       | 12 ++++++++----

 drivers/net/slip/slip.c       |  2 +-

 4 files changed, 15 insertions(+), 15 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;

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c

index ed00446759b2..9a863c6a6a33 100644

--- a/drivers/net/ppp/ppp_generic.c

+++ b/drivers/net/ppp/ppp_generic.c

@@ -721,10 +721,8 @@ 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 079f7adfcde5..27ed25252aac 100644

--- a/drivers/net/slip/slhc.c

+++ b/drivers/net/slip/slhc.c

@@ -84,8 +84,9 @@ 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)

@@ -94,11 +95,14 @@ 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)

@@ -106,7 +110,7 @@ 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)

@@ -141,7 +145,7 @@ 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 05387b1e2e95..a17d86a57734 100644

--- 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);

-- 

2.4.3