[PATCH-next] x86/kernel: Fix unchecked return value

[PATCH-next] x86/kernel: Fix unchecked return value

[Khaled ROMDHANI]

From the coverity scan analysis, the return value from
insn_decode_kernel is not checked. It is a macro constructed
from the insn_decode function which may fail and return
negative integer. Fix this by explicitly checking the
return value.

Addresses-Coverity: ("Unchecked return value")
Signed-off-by: Khaled ROMDHANI <khaledromdhani216@gmail.com>
---
 arch/x86/kernel/jump_label.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index a762dc1c615e..bf0ea003b6e7 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -23,7 +23,7 @@ int arch_jump_entry_size(struct jump_entry *entry)
 {
 	struct insn insn = {};
 
-	insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
+	WARN_ON(insn_decode_kernel(&insn, (void *)jump_entry_code(entry)));
 	BUG_ON(insn.length != 2 && insn.length != 5);
 
 	return insn.length;
-- 
2.17.1

Re: [PATCH-next] x86/kernel: Fix unchecked return value

[Borislav Petkov]

On Sat, May 15, 2021 at 09:22:12PM +0100, Khaled ROMDHANI wrote:
> From the coverity scan analysis, the return value from
> insn_decode_kernel is not checked. It is a macro constructed
> from the insn_decode function which may fail and return
> negative integer. Fix this by explicitly checking the
> return value.
> 
> Addresses-Coverity: ("Unchecked return value")
> Signed-off-by: Khaled ROMDHANI <khaledromdhani216@gmail.com>
> ---
>  arch/x86/kernel/jump_label.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index a762dc1c615e..bf0ea003b6e7 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -23,7 +23,7 @@ int arch_jump_entry_size(struct jump_entry *entry)
>  {
>  	struct insn insn = {};
>  
> -	insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
> +	WARN_ON(insn_decode_kernel(&insn, (void *)jump_entry_code(entry)));

I don't think coverity is smart enough to notice...

>  	BUG_ON(insn.length != 2 && insn.length != 5);
	^^^^^^^^^^^^^

... this line.


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH-next] x86/kernel: Fix unchecked return value

[Colin Ian King]

On 15/05/2021 21:36, Borislav Petkov wrote:
> On Sat, May 15, 2021 at 09:22:12PM +0100, Khaled ROMDHANI wrote:
>> From the coverity scan analysis, the return value from
>> insn_decode_kernel is not checked. It is a macro constructed
>> from the insn_decode function which may fail and return
>> negative integer. Fix this by explicitly checking the
>> return value.
>>
>> Addresses-Coverity: ("Unchecked return value")
>> Signed-off-by: Khaled ROMDHANI <khaledromdhani216@gmail.com>
>> ---
>>  arch/x86/kernel/jump_label.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
>> index a762dc1c615e..bf0ea003b6e7 100644
>> --- a/arch/x86/kernel/jump_label.c
>> +++ b/arch/x86/kernel/jump_label.c
>> @@ -23,7 +23,7 @@ int arch_jump_entry_size(struct jump_entry *entry)
>>  {
>>  	struct insn insn = {};
>>  
>> -	insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
>> +	WARN_ON(insn_decode_kernel(&insn, (void *)jump_entry_code(entry)));
> 
> I don't think coverity is smart enough to notice...
> 
>>  	BUG_ON(insn.length != 2 && insn.length != 5);
> 	^^^^^^^^^^^^^
> 
> ... this line.
> 
> 
Indeed. One needs to be careful with false positives with Coverity.

Colin

Re: [PATCH-next] x86/kernel: Fix unchecked return value

[Khaled Romdhani]

On Sat, May 15, 2021 at 09:51:23PM +0100, Colin Ian King wrote:
> On 15/05/2021 21:36, Borislav Petkov wrote:
> > On Sat, May 15, 2021 at 09:22:12PM +0100, Khaled ROMDHANI wrote:
> >> From the coverity scan analysis, the return value from
> >> insn_decode_kernel is not checked. It is a macro constructed
> >> from the insn_decode function which may fail and return
> >> negative integer. Fix this by explicitly checking the
> >> return value.
> >>
> >> Addresses-Coverity: ("Unchecked return value")
> >> Signed-off-by: Khaled ROMDHANI <khaledromdhani216@gmail.com>
> >> ---
> >>  arch/x86/kernel/jump_label.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> >> index a762dc1c615e..bf0ea003b6e7 100644
> >> --- a/arch/x86/kernel/jump_label.c
> >> +++ b/arch/x86/kernel/jump_label.c
> >> @@ -23,7 +23,7 @@ int arch_jump_entry_size(struct jump_entry *entry)
> >>  {
> >>  	struct insn insn = {};
> >>  
> >> -	insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
> >> +	WARN_ON(insn_decode_kernel(&insn, (void *)jump_entry_code(entry)));
> > 
> > I don't think coverity is smart enough to notice...
> > 
> >>  	BUG_ON(insn.length != 2 && insn.length != 5);
> > 	^^^^^^^^^^^^^
> > 
> > ... this line.
> > 
> > 
> Indeed. One needs to be careful with false positives with Coverity.
> 
> Colin

Yes. I shall be.

Thanks,

Khaled.