Re: [PATCH v2 1/2] ARM: Fix some check warnings of tool sparse

[Leizhen (ThunderTown)]

On 2022/10/10 18:20, Ard Biesheuvel wrote:
> On Mon, 10 Oct 2022 at 11:56, Zhen Lei <thunder.leizhen@xxxxxxxxxx> wrote:
>>
>> Fix the following warnings:
>>  warning: incorrect type in initializer (different address spaces)
>>     expected unsigned short [noderef] __user *register __p
>>     got unsigned short [usertype] *
>>  warning: cast removes address space '__user' of expression
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>> ---
>>  arch/arm/kernel/traps.c | 10 +++++-----
>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
>> index 20b2db6dcd1ced7..34aa80c09c508c1 100644
>> --- a/arch/arm/kernel/traps.c
>> +++ b/arch/arm/kernel/traps.c
>> @@ -188,9 +188,9 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
>>                         }
>>                 } else {
>>                         if (thumb)
>> -                               bad = get_user(val, &((u16 *)addr)[i]);
>> +                               bad = get_user(val, &((u16 __user *)addr)[i]);
>>                         else
>> -                               bad = get_user(val, &((u32 *)addr)[i]);
>> +                               bad = get_user(val, &((u32 __user *)addr)[i]);
>>                 }
>>
>>                 if (!bad)
>> @@ -455,15 +455,15 @@ asmlinkage void do_undefinstr(struct pt_regs *regs)
>>         if (processor_mode(regs) == SVC_MODE) {
>>  #ifdef CONFIG_THUMB2_KERNEL
>>                 if (thumb_mode(regs)) {
>> -                       instr = __mem_to_opcode_thumb16(((u16 *)pc)[0]);
>> +                       instr = __mem_to_opcode_thumb16(((__force u16 *)pc)[0]);
> 
> Shouldn't this be __user as well? (and below)

unsigned int instr;
void __user *pc;

The __user can clear the warning, but a new warning will be generated.

instr = __mem_to_opcode_thumb16(((u16 *)pc)[0]);
      ^new                           ^old

arch/arm/kernel/traps.c:473:33: warning: dereference of noderef expression

> 
>>                         if (is_wide_instruction(instr)) {
>>                                 u16 inst2;
>> -                               inst2 = __mem_to_opcode_thumb16(((u16 *)pc)[1]);
>> +                               inst2 = __mem_to_opcode_thumb16(((__force u16 *)pc)[1]);
>>                                 instr = __opcode_thumb32_compose(instr, inst2);
>>                         }
>>                 } else
>>  #endif
>> -                       instr = __mem_to_opcode_arm(*(u32 *) pc);
>> +                       instr = __mem_to_opcode_arm(*(__force u32 *) pc);
>>         } else if (thumb_mode(regs)) {
>>                 if (get_user(instr, (u16 __user *)pc))
>>                         goto die_sig;
>> --
>> 2.25.1
>>
>>
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> .
> 

-- 
Regards,
  Zhen Lei