[PATCH] fore200e: Fix incorrect checks of NULL pointer dereference

[PATCH] fore200e: Fix incorrect checks of NULL pointer dereference

[Aditya Pakki]

In fore200e_send and fore200e_close, the pointers from the arguments
are dereferenced in the variable declaration block and then checked
for NULL. The patch fixes these issues by avoiding NULL pointer
dereferences.

Signed-off-by: Aditya Pakki <pakki001@umn.edu>
---
 drivers/atm/fore200e.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/atm/fore200e.c b/drivers/atm/fore200e.c
index f1a500205313..8fbd36eb8941 100644
--- a/drivers/atm/fore200e.c
+++ b/drivers/atm/fore200e.c
@@ -1414,12 +1414,14 @@ fore200e_open(struct atm_vcc *vcc)
 static void
 fore200e_close(struct atm_vcc* vcc)
 {
-    struct fore200e*        fore200e = FORE200E_DEV(vcc->dev);
     struct fore200e_vcc*    fore200e_vcc;
+    struct fore200e*        fore200e;
     struct fore200e_vc_map* vc_map;
     unsigned long           flags;
 
     ASSERT(vcc);
+    fore200e = FORE200E_DEV(vcc->dev);
+
     ASSERT((vcc->vpi >= 0) && (vcc->vpi < 1<<FORE200E_VPI_BITS));
     ASSERT((vcc->vci >= 0) && (vcc->vci < 1<<FORE200E_VCI_BITS));
 
@@ -1464,10 +1466,10 @@ fore200e_close(struct atm_vcc* vcc)
 static int
 fore200e_send(struct atm_vcc *vcc, struct sk_buff *skb)
 {
-    struct fore200e*        fore200e     = FORE200E_DEV(vcc->dev);
-    struct fore200e_vcc*    fore200e_vcc = FORE200E_VCC(vcc);
+    struct fore200e*        fore200e;
+    struct fore200e_vcc*    fore200e_vcc;
     struct fore200e_vc_map* vc_map;
-    struct host_txq*        txq          = &fore200e->host_txq;
+    struct host_txq*        txq;
     struct host_txq_entry*  entry;
     struct tpd*             tpd;
     struct tpd_haddr        tpd_haddr;
@@ -1480,9 +1482,18 @@ fore200e_send(struct atm_vcc *vcc, struct sk_buff *skb)
     unsigned char*          data;
     unsigned long           flags;
 
-    ASSERT(vcc);
-    ASSERT(fore200e);
-    ASSERT(fore200e_vcc);
+    if (!vcc)
+        return -EINVAL;
+
+    fore200e = FORE200E_DEV(vcc->dev);
+    fore200e_vcc = FORE200E_VCC(vcc);
+
+    if (!fore200e)
+        return -EINVAL;
+
+    txq = &fore200e->host_txq;
+    if (!fore200e_vcc)
+        return -EINVAL;
 
     if (!test_bit(ATM_VF_READY, &vcc->flags)) {
 	DPRINTK(1, "VC %d.%d.%d not ready for tx\n", vcc->itf, vcc->vpi, vcc->vpi);
-- 
2.20.1

Re: [PATCH] fore200e: Fix incorrect checks of NULL pointer dereference

[Markus Elfring]

> The patch fixes these issues by avoiding NULL pointer dereferences.

I suggest to choose a better wording for this change description.

Will the tag “Fixes” become helpful here?


…
> +++ b/drivers/atm/fore200e.c
…
> @@ -1480,9 +1482,18 @@ fore200e_send(struct atm_vcc *vcc, struct sk_buff *skb)
…
> +    fore200e = FORE200E_DEV(vcc->dev);
> +    fore200e_vcc = FORE200E_VCC(vcc);
> +
> +    if (!fore200e)
> +        return -EINVAL;
> +
> +    txq = &fore200e->host_txq;
> +    if (!fore200e_vcc)
> +        return -EINVAL;
>
>      if (!test_bit(ATM_VF_READY, &vcc->flags)) {
…


Can the following adjustment be nicer?

+    fore200e_vcc = FORE200E_VCC(vcc);
+    if (!fore200e_vcc)
+        return -EINVAL;
+
+    fore200e = FORE200E_DEV(vcc->dev);
+    if (!fore200e)
+        return -EINVAL;
+
+    txq = &fore200e->host_txq;


Regards,
Markus

Re: [PATCH] fore200e: Fix incorrect checks of NULL pointer dereference

[David Miller]

From: Aditya Pakki <pakki001@umn.edu>
Date: Sun, 15 Dec 2019 10:14:51 -0600

> In fore200e_send and fore200e_close, the pointers from the arguments
> are dereferenced in the variable declaration block and then checked
> for NULL. The patch fixes these issues by avoiding NULL pointer
> dereferences.
> 
> Signed-off-by: Aditya Pakki <pakki001@umn.edu>

Applied to net-next.