Re: [bug report] firmware: arm_ffa: Add schedule receiver callback mechanism

[Sudeep Holla <sudeep.holla@arm.com>]

On Mon, Oct 30, 2023 at 05:31:04PM +0300, Dan Carpenter wrote:
> Hello Sudeep Holla,
> 
> The patch 0184450b8b1e: "firmware: arm_ffa: Add schedule receiver
> callback mechanism" from Oct 5, 2023 (linux-next), leads to the
> following Smatch static checker warning:
> 
> 	drivers/firmware/arm_ffa/driver.c:1251 ffa_partitions_cleanup()
> 	warn: double check that we're allocating correct size: 8 vs 88
> 
> drivers/firmware/arm_ffa/driver.c
>     1243 static void ffa_partitions_cleanup(void)
>     1244 {
>     1245         struct ffa_dev_part_info **info;
>     1246         int idx, count = drv_info->partition_count;
>     1247 
>     1248         if (!count)
>     1249                 return;
>     1250 
> --> 1251         info = kcalloc(count, sizeof(**info), GFP_KERNEL);
> 
> I *think* this should be sizeof(*info).  It ends up being a smaller
> allocation (8 bytes instead of 88).

Not sure if I am following this warning properly. I am bit confused whether
it suggest 8 is correct or 88 is correct. Anyways, the expectation is to
just allocate 8 bytes for a pointer. We just fetch a list of stored pointer
in XArray and free them.

One possible way to avoid any confusion is to use sizeof(struct ffa_dev_part_info *)
or even sizeof(void *).

> 
>     1252         if (!info)
>     1253                 return;
>     1254 
>     1255         xa_extract(&drv_info->partition_info, (void **)info, 0, VM_ID_MASK,
> 
> We copy count pointers to info.  We don't copy entire structs.  It still
> works but it's larger than necessary.
>

Yes, that is the expected behaviour. We copy the pointers that were allocated
in the setup and free them here.

-- 
Regards,
Sudeep

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