[RESENT PATCH] mmc: block: fix ABI regression of mmc_blk_ioctl

[RESENT PATCH] mmc: block: fix ABI regression of mmc_blk_ioctl

[Shawn Lin]

We should return -EINVAL if cmd is not MMC_IOC_CMD or MMC_IOC_MULTI_CMD,
otherwise blkdev_roset will return -EPERM.

Android-adb calls make_block_device_writable with ioctl(BLKROSET), which
will return error, make remount failed:
remount of /system failed;
couldn't make block device writable: Operation not permitted

openat(AT_FDCWD, "/dev/block/platform/ff420000.dwmmc/by-name/system", O_RDONLY) = 3
ioctl(3, BLKROSET, 0)  = -1 EPERM (Operation not permitted)

Fixes: a5f5774c55a2 ("mmc: block: Add new ioctl to send multi commands")
Cc: stable@vger.kernel.org
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
---

 drivers/mmc/card/block.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 47bc87d..170f099 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -688,6 +688,9 @@ cmd_err:
 static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
 	unsigned int cmd, unsigned long arg)
 {
+	if (cmd != MMC_IOC_CMD && cmd != MMC_IOC_MULTI_CMD)
+		return -EINVAL;
+
 	/*
 	 * The caller must have CAP_SYS_RAWIO, and must be calling this on the
 	 * whole block device, not on a partition.  This prevents overspray
-- 
2.3.7

Re: [RESENT PATCH] mmc: block: fix ABI regression of mmc_blk_ioctl

[John Stultz]

On Mon, Mar 7, 2016 at 1:59 PM, Shawn Lin <shawn.lin@rock-chips.com> wrote:
> We should return -EINVAL if cmd is not MMC_IOC_CMD or MMC_IOC_MULTI_CMD,
> otherwise blkdev_roset will return -EPERM.
>
> Android-adb calls make_block_device_writable with ioctl(BLKROSET), which
> will return error, make remount failed:
> remount of /system failed;
> couldn't make block device writable: Operation not permitted
>
> openat(AT_FDCWD, "/dev/block/platform/ff420000.dwmmc/by-name/system", O_RDONLY) = 3
> ioctl(3, BLKROSET, 0)  = -1 EPERM (Operation not permitted)
>
> Fixes: a5f5774c55a2 ("mmc: block: Add new ioctl to send multi commands")
> Cc: stable@vger.kernel.org
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>


Ulf,
   We're hitting this as well, and Shawn's patch seems to fix it for me.

Tested-by: John Stultz <john.stultz@linaro.org>

Thanks Shawn!
-john

Re: [RESENT PATCH] mmc: block: fix ABI regression of mmc_blk_ioctl

[Jon Hunter]

On 07/03/16 06:59, Shawn Lin wrote:
> We should return -EINVAL if cmd is not MMC_IOC_CMD or MMC_IOC_MULTI_CMD,
> otherwise blkdev_roset will return -EPERM.
> 
> Android-adb calls make_block_device_writable with ioctl(BLKROSET), which
> will return error, make remount failed:
> remount of /system failed;
> couldn't make block device writable: Operation not permitted

I think you should elaborate here why the behaviour between -EINVAL and
-EPERM is different as they are both errors. In other words, add your
comment about how the ADB code is checking for a supported command.

> openat(AT_FDCWD, "/dev/block/platform/ff420000.dwmmc/by-name/system", O_RDONLY) = 3
> ioctl(3, BLKROSET, 0)  = -1 EPERM (Operation not permitted)
> 
> Fixes: a5f5774c55a2 ("mmc: block: Add new ioctl to send multi commands")
> Cc: stable@vger.kernel.org
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
> ---
> 
>  drivers/mmc/card/block.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 47bc87d..170f099 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -688,6 +688,9 @@ cmd_err:
>  static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
>  	unsigned int cmd, unsigned long arg)
>  {
> +	if (cmd != MMC_IOC_CMD && cmd != MMC_IOC_MULTI_CMD)
> +		return -EINVAL;
> +
>  	/*
>  	 * The caller must have CAP_SYS_RAWIO, and must be calling this on the
>  	 * whole block device, not on a partition.  This prevents overspray

The change is fine with me, but I agree with Seshagiri's comment that
instead of the above, move the following test to the mmc_blk_ioctl_cmd
and mmc_blk_ioctl_multi_cmd functions:

if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
                return -EPERM;

There is a case statement that then would return -EINVAL if the command
is not supported.

If you look at V3 of the patch "mmc: block: Add new ioctl to send multi
commands" [0] this is how we had it and only in V4 (the final version)
did we move it.

Cheers
Jon

[0] http://marc.info/?l=linux-mmc&m=144224289716299&w=2

Re: [RESENT PATCH] mmc: block: fix ABI regression of mmc_blk_ioctl

[Shawn Lin]

On 2016/3/9 18:50, Jon Hunter wrote:
>
> On 07/03/16 06:59, Shawn Lin wrote:
>> We should return -EINVAL if cmd is not MMC_IOC_CMD or MMC_IOC_MULTI_CMD,
>> otherwise blkdev_roset will return -EPERM.
>>
>> Android-adb calls make_block_device_writable with ioctl(BLKROSET), which
>> will return error, make remount failed:
>> remount of /system failed;
>> couldn't make block device writable: Operation not permitted
>
> I think you should elaborate here why the behaviour between -EINVAL and
> -EPERM is different as they are both errors. In other words, add your
> comment about how the ADB code is checking for a supported command.

yep. So if need to send v2 after comment from Ulf, I will add more into
commit-msg.

>
>> openat(AT_FDCWD, "/dev/block/platform/ff420000.dwmmc/by-name/system", O_RDONLY) = 3
>> ioctl(3, BLKROSET, 0)  = -1 EPERM (Operation not permitted)
>>
>> Fixes: a5f5774c55a2 ("mmc: block: Add new ioctl to send multi commands")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
>> ---
>>
>>   drivers/mmc/card/block.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>> index 47bc87d..170f099 100644
>> --- a/drivers/mmc/card/block.c
>> +++ b/drivers/mmc/card/block.c
>> @@ -688,6 +688,9 @@ cmd_err:
>>   static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
>>   	unsigned int cmd, unsigned long arg)
>>   {
>> +	if (cmd != MMC_IOC_CMD && cmd != MMC_IOC_MULTI_CMD)
>> +		return -EINVAL;
>> +
>>   	/*
>>   	 * The caller must have CAP_SYS_RAWIO, and must be calling this on the
>>   	 * whole block device, not on a partition.  This prevents overspray
>
> The change is fine with me, but I agree with Seshagiri's comment that
> instead of the above, move the following test to the mmc_blk_ioctl_cmd
> and mmc_blk_ioctl_multi_cmd functions:
>
> if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
>                  return -EPERM;
>

right, and both are ok to me :).
Adding this check for mmc_blk_ioctl_cmd and mmc_blk_ioctl_multi_cmd
respectively may also looks like we produce two some code sections that 
do the same thing.

I think it depends on how Ulf want the solution to be? Let's wait for
Ulf' comment.

> There is a case statement that then would return -EINVAL if the command
> is not supported.
>
> If you look at V3 of the patch "mmc: block: Add new ioctl to send multi
> commands" [0] this is how we had it and only in V4 (the final version)
> did we move it.

yes, I read V3 and V4 both to see how the patch was going. Thanks for
sharing it.

>
> Cheers
> Jon
>
> [0] http://marc.info/?l=linux-mmc&m=144224289716299&w=2
> --
> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
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>

Re: [RESENT PATCH] mmc: block: fix ABI regression of mmc_blk_ioctl

[Ulf Hansson]

On 9 March 2016 at 14:51, Shawn Lin <shawn.lin@kernel-upstream.org> wrote:
> On 2016/3/9 18:50, Jon Hunter wrote:
>>
>>
>> On 07/03/16 06:59, Shawn Lin wrote:
>>>
>>> We should return -EINVAL if cmd is not MMC_IOC_CMD or MMC_IOC_MULTI_CMD,
>>> otherwise blkdev_roset will return -EPERM.
>>>
>>> Android-adb calls make_block_device_writable with ioctl(BLKROSET), which
>>> will return error, make remount failed:
>>> remount of /system failed;
>>> couldn't make block device writable: Operation not permitted
>>
>>
>> I think you should elaborate here why the behaviour between -EINVAL and
>> -EPERM is different as they are both errors. In other words, add your
>> comment about how the ADB code is checking for a supported command.
>
>
> yep. So if need to send v2 after comment from Ulf, I will add more into
> commit-msg.
>
>
>>
>>> openat(AT_FDCWD, "/dev/block/platform/ff420000.dwmmc/by-name/system",
>>> O_RDONLY) = 3
>>> ioctl(3, BLKROSET, 0)  = -1 EPERM (Operation not permitted)
>>>
>>> Fixes: a5f5774c55a2 ("mmc: block: Add new ioctl to send multi commands")
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
>>> ---
>>>
>>>   drivers/mmc/card/block.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>>> index 47bc87d..170f099 100644
>>> --- a/drivers/mmc/card/block.c
>>> +++ b/drivers/mmc/card/block.c
>>> @@ -688,6 +688,9 @@ cmd_err:
>>>   static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
>>>         unsigned int cmd, unsigned long arg)
>>>   {
>>> +       if (cmd != MMC_IOC_CMD && cmd != MMC_IOC_MULTI_CMD)
>>> +               return -EINVAL;
>>> +
>>>         /*
>>>          * The caller must have CAP_SYS_RAWIO, and must be calling this
>>> on the
>>>          * whole block device, not on a partition.  This prevents
>>> overspray
>>
>>
>> The change is fine with me, but I agree with Seshagiri's comment that
>> instead of the above, move the following test to the mmc_blk_ioctl_cmd
>> and mmc_blk_ioctl_multi_cmd functions:
>>
>> if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
>>                  return -EPERM;
>>
>
> right, and both are ok to me :).
> Adding this check for mmc_blk_ioctl_cmd and mmc_blk_ioctl_multi_cmd
> respectively may also looks like we produce two some code sections that do
> the same thing.
>
> I think it depends on how Ulf want the solution to be? Let's wait for
> Ulf' comment.
>

I believe I prefer Jon/Seshagiri suggestions for this. It makes the
code a bit more readable.

Please send a v2 addressing their comments.

Kind regards
Uffe