[PATCH] RISC-V: hwprobe: Check for the reserved flags

[Palmer Dabbelt]

On Wed, 03 Jan 2024 05:23:57 PST (-0800), ajones at ventanamicro.com wrote:
> Hi Palmer,
>
> On Wed, Jan 03, 2024 at 04:12:20AM -0800, Palmer Dabbelt wrote:
>> This check got dropped when RISCV_HWPROBE_WHICH_CPUS was added, but
>> we've still got a bunch of other reserved flags.  So check for them,
>> just to make sure userspace doesn't get confused later.
>>
>> Fixes: e178bf146e4b ("RISC-V: hwprobe: Introduce which-cpus flag")
>
> I'm having trouble finding the tree/branch for this commit hash.

It's just over here 
<https://git.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git/log/?h=for-next>, 
that's where I push stuff before it goes to my testing box.  Something 
rebooted, though, so it ended up tied up for a bit...

>
>> Signed-off-by: Palmer Dabbelt <palmer at rivosinc.com>
>> ---
>>  arch/riscv/kernel/sys_hwprobe.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
>> index ccf61b040536..10d72893b04f 100644
>> --- a/arch/riscv/kernel/sys_hwprobe.c
>> +++ b/arch/riscv/kernel/sys_hwprobe.c
>> @@ -347,6 +347,10 @@ static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
>>  			    unsigned long __user *cpus_user,
>>  			    unsigned int flags)
>>  {
>> +	/* The rest of the flags are still reserved. */
>> +	if (flags & ~RISCV_HWPROBE_WICHH_CPUS)
>                                    ^ WHICH
>
>
> We shouldn't need this check since the way v3 of the series has
> do_riscv_hwprobe() is
>
>  static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
>                            size_t pair_count, size_t cpusetsize,
>                            unsigned long __user *cpus_user,
>                            unsigned int flags)
>  {
>        if (flags & RISCV_HWPROBE_WHICH_CPUS)
>                return hwprobe_get_cpus(pairs, pair_count, cpusetsize,
>                                        cpus_user, flags);
>
>        return hwprobe_get_values(pairs, pair_count, cpusetsize,
>                                  cpus_user, flags);
>  }
>
> And hwprobe_get_cpus() starts with this check
>
>       if (flags != RISCV_HWPROBE_WHICH_CPUS)
>                return -EINVAL;
>
> And hwprobe_get_values() starts with the original check
>
>       /* Check the reserved flags. */
>       if (flags != 0)
>               return -EINVAL;
>
>
> IOW, we don't check flags at the top level, but each branch checks for its
> flags and hwprobe_get_values() doesn't have any.

Ya, sorry, I think I was just still asleep.

>
> Thanks,
> drew
>
>> +		return -EINVAL;
>> +
>>  	if (flags & RISCV_HWPROBE_WHICH_CPUS)
>>  		return hwprobe_get_cpus(pairs, pair_count, cpusetsize,
>>  					cpus_user, flags);
>> --
>> 2.43.0
>>