diff mbox

[2/2] regmap: Add range check in _regmap_raw_write()

Message ID 1424335255-7517-1-git-send-email-srinivas.kandagatla@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Srinivas Kandagatla Feb. 19, 2015, 8:40 a.m. UTC
regmap_bulk_write() ends up using the path that invokes _regmap_raw_write(),
however _regmap_raw_write() never checks if the registers that are accessed
are actually within the accessible range. This results in kernel crashes when
trying to access registers beyond max_registers.

This patch just adds check before accessing the register range.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
 drivers/base/regmap/regmap.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

Comments

Mark Brown Feb. 19, 2015, 10:31 a.m. UTC | #1
On Thu, Feb 19, 2015 at 08:40:55AM +0000, Srinivas Kandagatla wrote:
> regmap_bulk_write() ends up using the path that invokes _regmap_raw_write(),
> however _regmap_raw_write() never checks if the registers that are accessed
> are actually within the accessible range. This results in kernel crashes when
> trying to access registers beyond max_registers.
> 
> This patch just adds check before accessing the register range.

>  	/* Check for unwritable registers before we start */
> -	if (map->writeable_reg)
> -		for (i = 0; i < val_len / map->format.val_bytes; i++)
> -			if (!map->writeable_reg(map->dev,
> -						reg + (i * map->reg_stride)))
> -				return -EINVAL;
> +	for (i = 0; i < count; i++)
> +		if (!regmap_writeable(map, reg + (i * map->reg_stride)))
> +			return -EINVAL;

Your changelog doesn't correspond to what the code is actually doing
here...  what you're actually doing here is replacing an open coding of
regmap_writeable() with calls to the function.

The same papering over the cracks concerns do apply here as well, it's
not immediately obvious that this is a good fix for the issue you
describe.
Srinivas Kandagatla Feb. 19, 2015, 11:11 a.m. UTC | #2
On 19/02/15 10:31, Mark Brown wrote:
> On Thu, Feb 19, 2015 at 08:40:55AM +0000, Srinivas Kandagatla wrote:
>> regmap_bulk_write() ends up using the path that invokes _regmap_raw_write(),
>> however _regmap_raw_write() never checks if the registers that are accessed
>> are actually within the accessible range. This results in kernel crashes when
>> trying to access registers beyond max_registers.
>>
>> This patch just adds check before accessing the register range.
>
>>   	/* Check for unwritable registers before we start */
>> -	if (map->writeable_reg)
>> -		for (i = 0; i < val_len / map->format.val_bytes; i++)
>> -			if (!map->writeable_reg(map->dev,
>> -						reg + (i * map->reg_stride)))
>> -				return -EINVAL;
>> +	for (i = 0; i < count; i++)
>> +		if (!regmap_writeable(map, reg + (i * map->reg_stride)))
>> +			return -EINVAL;
>
> Your changelog doesn't correspond to what the code is actually doing
> here...  what you're actually doing here is replacing an open coding of
> regmap_writeable() with calls to the function.
>
> The same papering over the cracks concerns do apply here as well, it's
> not immediately obvious that this is a good fix for the issue you
> describe.
Only reason for me to send this patch was that fact that 
_regmap_raw_write() also suffers from same issue as _regmap_raw_read(), 
which is "access beyond max_register".

Should I drop this patch?
Or
Adding similar check of max_register before the writing makes sense?


--srini
Mark Brown Feb. 19, 2015, 11:55 a.m. UTC | #3
On Thu, Feb 19, 2015 at 11:11:58AM +0000, Srinivas Kandagatla wrote:
> On 19/02/15 10:31, Mark Brown wrote:

> >Your changelog doesn't correspond to what the code is actually doing
> >here...  what you're actually doing here is replacing an open coding of
> >regmap_writeable() with calls to the function.

> Only reason for me to send this patch was that fact that _regmap_raw_write()
> also suffers from same issue as _regmap_raw_read(), which is "access beyond
> max_register".

> Should I drop this patch?
> Or
> Adding similar check of max_register before the writing makes sense?

No, please go and reread your patch - neither your description above nor
the changelog match up with what it's actually doing.  It looks like a
perfectly sensible patch, it just doesn't do what you're saying it does.
diff mbox

Patch

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index d480e49..32ce7b3 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1202,16 +1202,14 @@  int _regmap_raw_write(struct regmap *map, unsigned int reg,
 	void *buf;
 	int ret = -ENOTSUPP;
 	size_t len;
-	int i;
+	int i, count = val_len/map->format.val_bytes;
 
 	WARN_ON(!map->bus);
 
 	/* Check for unwritable registers before we start */
-	if (map->writeable_reg)
-		for (i = 0; i < val_len / map->format.val_bytes; i++)
-			if (!map->writeable_reg(map->dev,
-						reg + (i * map->reg_stride)))
-				return -EINVAL;
+	for (i = 0; i < count; i++)
+		if (!regmap_writeable(map, reg + (i * map->reg_stride)))
+			return -EINVAL;
 
 	if (!map->cache_bypass && map->format.parse_val) {
 		unsigned int ival;