Re: [PATCH] scsi: fcoe: sanity check string size for store_ctrl_mode option

2017-03-23 Thread Dan Carpenter 
On Wed, Mar 22, 2017 at 07:42:08PM +, Colin Ian King wrote:
> On 22/03/17 19:39, Dan Carpenter wrote:
> > On Wed, Mar 22, 2017 at 02:01:37PM +, Colin King wrote:
> >> From: Colin Ian King 
> >>
> >> Reading and writing to mode[count - 1] implies the count should not
> >> be less than 1 so add a sanity check for this.
> >>
> >> Detected with CoverityScan, CID#1357345 ("Overflowed array index write")
> >>
> >> Signed-off-by: Colin Ian King 
> > 
> > This is harmless, of course, but count can't be zero.  This is a sysfs
> > file so we test for zero size writes in sysfs_kf_write() and return
> > early.
> 
> Ah, thanks for pointing out that. I overlooked that detail.
> 

The only reason I know this stuff is because it's annotated in Smatch.
So I do this:

diff --git a/drivers/scsi/fcoe/fcoe_sysfs.c b/drivers/scsi/fcoe/fcoe_sysfs.c
index 9cf3d56296ab..c491ad8fb0a8 100644
--- a/drivers/scsi/fcoe/fcoe_sysfs.c
+++ b/drivers/scsi/fcoe/fcoe_sysfs.c
@@ -281,6 +281,7 @@ static ssize_t show_ctlr_mode(struct device *dev,
"%s\n", name);
 }
 
+#include "/home/dcarpenter/progs/smatch/devel/check_debug.h"
 static ssize_t store_ctlr_mode(struct device *dev,
   struct device_attribute *attr,
   const char *buf, size_t count)
@@ -288,6 +289,7 @@ static ssize_t store_ctlr_mode(struct device *dev,
struct fcoe_ctlr_device *ctlr = dev_to_ctlr(dev);
char mode[FCOE_MAX_MODENAME_LEN + 1];
 
+   __smatch_implied(count);
if (count > FCOE_MAX_MODENAME_LEN)
return -EINVAL;
 

Then when I run kchecker drivers/scsi/fcoe/fcoe_sysfs.c, it tells me:

drivers/scsi/fcoe/fcoe_sysfs.c:292 store_ctlr_mode() implied: count = 
'1-10,2147479552'

Which is sort of surprising...  The 10 value is a hack I made so
that it would never complain that "off + count" will wrap.  But
apparently something has changed so it's also picking up the true limit
of count which is 2147479552.

Then I run the following commands to view the call tree:
smdb.py store_ctlr_mode
smdb.py dev_attr_store
smdb.py sysfs_kf_write
I have some vim macros so I can look these up really quickly.

regards,
dan carpenter

Re: [PATCH] scsi: fcoe: sanity check string size for store_ctrl_mode option

2017-03-22 Thread Colin Ian King 
On 22/03/17 19:39, Dan Carpenter wrote:
> On Wed, Mar 22, 2017 at 02:01:37PM +, Colin King wrote:
>> From: Colin Ian King 
>>
>> Reading and writing to mode[count - 1] implies the count should not
>> be less than 1 so add a sanity check for this.
>>
>> Detected with CoverityScan, CID#1357345 ("Overflowed array index write")
>>
>> Signed-off-by: Colin Ian King 
> 
> This is harmless, of course, but count can't be zero.  This is a sysfs
> file so we test for zero size writes in sysfs_kf_write() and return
> early.

Ah, thanks for pointing out that. I overlooked that detail.

Colin

> 
> regards,
> dan carpenter
>

Re: [PATCH] scsi: fcoe: sanity check string size for store_ctrl_mode option

2017-03-22 Thread Dan Carpenter 
On Wed, Mar 22, 2017 at 02:01:37PM +, Colin King wrote:
> From: Colin Ian King 
> 
> Reading and writing to mode[count - 1] implies the count should not
> be less than 1 so add a sanity check for this.
> 
> Detected with CoverityScan, CID#1357345 ("Overflowed array index write")
> 
> Signed-off-by: Colin Ian King 

This is harmless, of course, but count can't be zero.  This is a sysfs
file so we test for zero size writes in sysfs_kf_write() and return
early.

regards,
dan carpenter