Patchwork [v2] mtd: sm_ftl: heap corruption in sm_create_sysfs_attributes()

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Submitter Dan Carpenter
Date Dec. 5, 2013, 2:53 p.m.
Message ID <20131205145349.GA13302@elgon.mountain>
Download mbox | patch
Permalink /patch/297163/
State Accepted
Commit b4c233057771581698a13694ab6f33b48ce837dc
Headers show

Comments

Dan Carpenter - Dec. 5, 2013, 2:53 p.m.
We always put a NUL terminator one space past the end of the "vendor"
buffer.  Walter Harms also pointed out that this should just use
kstrndup().

Fixes: 7d17c02a01a1 ('mtd: Add new SmartMedia/xD FTL')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2:  Use kstrndup().
     Don't subtract 1 from the strnlen() limiter for the NUL.  I think
     it's ok to go over?
Brian Norris - Jan. 28, 2014, 5:32 a.m.
On Thu, Dec 05, 2013 at 05:53:50PM +0300, Dan Carpenter wrote:
> We always put a NUL terminator one space past the end of the "vendor"
> buffer.  Walter Harms also pointed out that this should just use
> kstrndup().
> 
> Fixes: 7d17c02a01a1 ('mtd: Add new SmartMedia/xD FTL')
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Patch looks good.

> ---
> v2:  Use kstrndup().
>      Don't subtract 1 from the strnlen() limiter for the NUL.  I think
>      it's ok to go over?

I don't think you're "going over" anything. You're just (correctly)
allocating the buffer as (at most) one byte larger than (SM_SMALL_PAGE -
SM_CIS_VENDOR_OFFSET), which is perfect if you're copying up to
(SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET) bytes of character data.

Pushed to l2-mtd.git/next, queued for 3.15. Thanks.

Brian

Patch

diff --git a/drivers/mtd/sm_ftl.c b/drivers/mtd/sm_ftl.c
index 4b8e89583f2a..cf49c22673b9 100644
--- a/drivers/mtd/sm_ftl.c
+++ b/drivers/mtd/sm_ftl.c
@@ -59,15 +59,12 @@  static struct attribute_group *sm_create_sysfs_attributes(struct sm_ftl *ftl)
 	struct attribute_group *attr_group;
 	struct attribute **attributes;
 	struct sm_sysfs_attribute *vendor_attribute;
+	char *vendor;
 
-	int vendor_len = strnlen(ftl->cis_buffer + SM_CIS_VENDOR_OFFSET,
-					SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET);
-
-	char *vendor = kmalloc(vendor_len, GFP_KERNEL);
+	vendor = kstrndup(ftl->cis_buffer + SM_CIS_VENDOR_OFFSET,
+			  SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET, GFP_KERNEL);
 	if (!vendor)
 		goto error1;
-	memcpy(vendor, ftl->cis_buffer + SM_CIS_VENDOR_OFFSET, vendor_len);
-	vendor[vendor_len] = 0;
 
 	/* Initialize sysfs attributes */
 	vendor_attribute =
@@ -78,7 +75,7 @@  static struct attribute_group *sm_create_sysfs_attributes(struct sm_ftl *ftl)
 	sysfs_attr_init(&vendor_attribute->dev_attr.attr);
 
 	vendor_attribute->data = vendor;
-	vendor_attribute->len = vendor_len;
+	vendor_attribute->len = strlen(vendor);
 	vendor_attribute->dev_attr.attr.name = "vendor";
 	vendor_attribute->dev_attr.attr.mode = S_IRUGO;
 	vendor_attribute->dev_attr.show = sm_attr_show;