linux-kernel - Re: [PATCH] objtool: check: Fix NULL pointer dereference

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Message-ID: <883f3016-5156-8b84-b6aa-4f10a3bdb4eb@embeddedor.com>
Date:   Tue, 31 Mar 2020 17:27:40 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] objtool: check: Fix NULL pointer dereference



On 3/31/20 17:04, Josh Poimboeuf wrote:
> On Mon, Mar 30, 2020 at 07:20:40PM -0500, Gustavo A. R. Silva wrote:
>> In case func is null, there is a null pointer dereference at 2029:
>>
>> 2029                 WARN("%s uses BP as a scratch register",
>> 2030                      func->name);
>>
>> Fix this by null-checking func.
>>
>> Addresses-Coverity-ID: 1492002 ("Dereference after null check")
>> Fixes: c705cecc8431 ("objtool: Track original function across branches")
>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>> ---
>>  tools/objtool/check.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
>> index e3bb76358148..182cc48fa892 100644
>> --- a/tools/objtool/check.c
>> +++ b/tools/objtool/check.c
>> @@ -2025,7 +2025,7 @@ static int validate_return(struct symbol *func, struct instruction *insn, struct
>>  		return 1;
>>  	}
>>  
>> -	if (state->bp_scratch) {
>> +	if (func && state->bp_scratch) {
>>  		WARN("%s uses BP as a scratch register",
>>  		     func->name);
>>  		return 1;
> 
> We should still do the warning even if there's no func.  I'll make a
> slightly different patch which unconditionally uses WARN_FUNC().
> 

Awesome. :)

> I'll give you Reported-by credit and keep the coverity tag.  Thanks!
> 

Great.

Thanks
--
Gustavo