Re: [dm-devel] [PATCH] md: dm-ioctl: drop always-false condition

Sergey Shtylyov
2023-02-06T21:00:22Z

On 1/18/23 2:59 PM, Mikulas Patocka wrote:

[...]

>> The expression 'indata[3] > ULONG_MAX' always evaluates to false since
>> indata[] is declared as an array of *unsigned long* elements and #define
>> ULONG_MAX represents the max value of that exact type...
>>
>> Note that gcc seems to be able to detect the dead code here and eliminate
>> this check anyway...
>>
>> Found by Linux Verification Center (linuxtesting.org) with the SVACE static
>> analysis tool.
>>
>> Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
>
> Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>

Thank you!

>> ---
>> This patch is atop of the 'for-next' branch of the device-mapper repo...
>>
>> drivers/md/dm-ioctl.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> Index: linux-dm/drivers/md/dm-ioctl.c
>> ===================================================================
>> --- linux-dm.orig/drivers/md/dm-ioctl.c
>> +++ linux-dm/drivers/md/dm-ioctl.c
>> @@ -1073,8 +1073,7 @@ static int dev_set_geometry(struct file

Returning to this patch, I think I should've added the name of the function
in question in both the subject and and commit msg... I'll recast...

>> goto out;
>> }
>>
>> - if (indata[0] > 65535 || indata[1] > 255 ||
>> - indata[2] > 255 || indata[3] > ULONG_MAX) {
>> + if (indata[0] > 65535 || indata[1] > 255 || indata[2] > 255) {
>> DMERR("Geometry exceeds range limits.");
>> goto out;
>> }
>>

MBR, Sergey