On Wed, Mar 22, 2017 at 07:42:08PM +0000, Colin Ian King wrote:
> On 22/03/17 19:39, Dan Carpenter wrote:
> > On Wed, Mar 22, 2017 at 02:01:37PM +0000, Colin King wrote:
> >> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> >>
> >> 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 <colin.king@xxxxxxxxxxxxx>
> >
> > 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 = '1-1000000000,2147479552'
Which is sort of surprising... The 1000000000 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
