Re: [PATCH v1] perf disasm: Fix potential use-after-free on fileloc

[Athira Rajeev]

> On 7 Mar 2026, at 12:46 AM, Ian Rogers <irogers@xxxxxxxxxx> wrote:
> 
> The fileloc is a copy of a pointer to a string but in places like
> symbol_disassemble__llvm this string appears to be freed setting up
> potential use-after-frees:
> 
> llvm.c:
> ```
> dl = disasm_line__new(args);
> if (dl == NULL)
> goto err;
> 
> annotation_line__add(&dl->al, &notes->src->source);
> 
> free(args->fileloc);
> ```
> disasm.c:
> ```
> static void annotation_line__init(struct annotation_line *al,
>  struct annotate_args *args,
>  int nr)
> {
> al->offset = args->offset;
> al->line = strdup(args->line);
> al->line_nr = args->line_nr;
> al->fileloc = args->fileloc;
> al->data_nr = nr;
> }
> 
> struct disasm_line *disasm_line__new(struct annotate_args *args)
> {
> struct disasm_line *dl = NULL;
> struct annotation *notes = symbol__annotation(args->ms->sym);
> int nr = notes->src->nr_events;
> 
> dl = zalloc(disasm_line_size(nr));
> if (!dl)
> return NULL;
> 
> annotation_line__init(&dl->al, args, nr);
> ```
> 
> Fix this by making the fileloc a copy of the underlying string in its
> init/exit.
> 
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> ---
> tools/perf/util/disasm.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> index ddcc488f2e5f..b83bc14f82e1 100644
> --- a/tools/perf/util/disasm.c
> +++ b/tools/perf/util/disasm.c
> @@ -908,13 +908,14 @@ static void annotation_line__init(struct annotation_line *al,
> al->offset = args->offset;
> al->line = strdup(args->line);
> al->line_nr = args->line_nr;
> - al->fileloc = args->fileloc;
> + al->fileloc = args->fileloc ? strdup(args->fileloc) : NULL;
> al->data_nr = nr;
> }
> 
> static void annotation_line__exit(struct annotation_line *al)
> {
> zfree_srcline(&al->path);
> + zfree(&al->fileloc);
Looks good to me.

Reviewed-by: Athira Rajeev <atrajeev@xxxxxxxxxxxxx <mailto:atrajeev@xxxxxxxxxxxxx>>

Thanks
Athira

> zfree(&al->line);
> zfree(&al->cycles);
> zfree(&al->br_cntr);
> -- 
> 2.53.0.473.g4a7958ca14-goog
>