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

Josh Poimboeuf
2018-11-19T17:57:15Z

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@redhat.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