[PATCH] sdio: Read buffer overflow

[PATCH] sdio: Read buffer overflow

[Roel Kluin]

If the loop breaks with an index of 0, then we read before the array.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---
diff --git a/drivers/mmc/core/sdio_cis.c b/drivers/mmc/core/sdio_cis.c
index 963f293..0f8853c 100644
--- a/drivers/mmc/core/sdio_cis.c
+++ b/drivers/mmc/core/sdio_cis.c
@@ -40,7 +40,7 @@ static int cistpl_vers_1(struct mmc_card *card, struct sdio_func *func,
 			nr_strings++;
 	}
 
-	if (buf[i-1] != '\0') {
+	if (i != 0 && buf[i-1] != '\0') {
 		printk(KERN_WARNING "SDIO: ignoring broken CISTPL_VERS_1\n");
 		return 0;
 	}

Re: [PATCH] sdio: Read buffer overflow

[David Vrabel]

Roel Kluin wrote:
> If the loop breaks with an index of 0, then we read before the array.

This isn't a helpful subject or changelog comment really.  Suggest

sdio: avoid buffer underrun when parsing an invalid CISTPL_VERS_1

> Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
> ---
> diff --git a/drivers/mmc/core/sdio_cis.c b/drivers/mmc/core/sdio_cis.c
> index 963f293..0f8853c 100644
> --- a/drivers/mmc/core/sdio_cis.c
> +++ b/drivers/mmc/core/sdio_cis.c
> @@ -40,7 +40,7 @@ static int cistpl_vers_1(struct mmc_card *card, struct sdio_func *func,
>  			nr_strings++;
>  	}
>  
> -	if (buf[i-1] != '\0') {
> +	if (i != 0 && buf[i-1] != '\0') {

Looking at the PC Card 8.0 spec (vol 4, section 3.2.10) this test could
simply be:

if (nr_strings < 4) {

>  		printk(KERN_WARNING "SDIO: ignoring broken CISTPL_VERS_1\n");
>  		return 0;
>  	}
-- 
David Vrabel, Senior Software Engineer, Drivers
CSR, Churchill House, Cambridge Business Park,  Tel: +44 (0)1223 692562
Cowley Road, Cambridge, CB4 0WZ                 http://www.csr.com/


'member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom'

Re: [PATCH] sdio: Read buffer overflow

[Roel Kluin]

sdio: avoid buffer underrun when parsing an invalid CISTPL_VERS_1

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---
Thanks for comments,

diff --git a/drivers/mmc/core/sdio_cis.c b/drivers/mmc/core/sdio_cis.c
index 963f293..6636354 100644
--- a/drivers/mmc/core/sdio_cis.c
+++ b/drivers/mmc/core/sdio_cis.c
@@ -40,7 +40,7 @@ static int cistpl_vers_1(struct mmc_card *card, struct sdio_func *func,
 			nr_strings++;
 	}
 
-	if (buf[i-1] != '\0') {
+	if (nr_strings < 4) {
 		printk(KERN_WARNING "SDIO: ignoring broken CISTPL_VERS_1\n");
 		return 0;
 	}