linux-kernel - Re: [PATCH v3 1/2] objtool: fix failed cold symbol doublefree

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Message-ID: <20181119175710.6tcqxtevhg422wsg@treble>
Date:   Mon, 19 Nov 2018 11:57:10 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Artem Savkov <asavkov@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] objtool: fix failed cold symbol doublefree

On Mon, Nov 12, 2018 at 01:55:18PM +0100, Artem Savkov wrote:
> If read_symbols() fails during second list traversal (the one dealing
> with ".cold" subfunctions) it frees the symbol, but never deletes it
> from the list/hash_table resulting in symbol being freed again in
> elf_close().
> 
> Fixes: 13810435b9a7 "objtool: Support GCC 8's cold subfunctions"

This needs parentheses, like:

Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")

> Signed-off-by: Artem Savkov <asavkov@...hat.com>
> ---
>  tools/objtool/elf.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
> index 6dbb9fae0f9d..3decd43477df 100644
> --- a/tools/objtool/elf.c
> +++ b/tools/objtool/elf.c
> @@ -312,7 +312,7 @@ static int read_symbols(struct elf *elf)
>  			if (!pfunc) {
>  				WARN("%s(): can't find parent function",
>  				     sym->name);
> -				goto err;
> +				goto cold_err;

Since it will get freed properly in elf_close() anyway, maybe it would
be simpler to just 'return -1' here.

>  			}
>  
>  			sym->pfunc = pfunc;
> @@ -336,6 +336,9 @@ static int read_symbols(struct elf *elf)
>  
>  	return 0;
>  
> +cold_err:
> +	list_del(&sym->list);
> +	hash_del(&sym->hash);
>  err:
>  	free(sym);
>  	return -1;
> -- 
> 2.17.2
> 

-- 
Josh