[PATCH v2] perf disasm: Fix potential use-after-free on fileloc

[PATCH v2] perf disasm: Fix potential use-after-free on fileloc

[Ian Rogers]

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@google.com>
---
 tools/perf/util/disasm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index ddcc488f2e5f..3fcb3634a7e0 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);
 	zfree(&al->line);
 	zfree(&al->cycles);
 	zfree(&al->br_cntr);
@@ -950,7 +951,7 @@ struct disasm_line *disasm_line__new(struct annotate_args *args)
 
 	annotation_line__init(&dl->al, args, nr);
 	if (dl->al.line == NULL)
-		goto out_delete;
+		goto out_free_line;
 
 	if (args->offset != -1) {
 		if (arch__is_powerpc(args->arch)) {
@@ -965,8 +966,7 @@ struct disasm_line *disasm_line__new(struct annotate_args *args)
 	return dl;
 
 out_free_line:
-	zfree(&dl->al.line);
-out_delete:
+	annotation_line__exit(&dl->al);
 	free(dl);
 	return NULL;
 }
-- 
2.53.0.473.g4a7958ca14-goog

Re: [PATCH v2] perf disasm: Fix potential use-after-free on fileloc

[Namhyung Kim]

On Fri, Mar 06, 2026 at 04:22:22PM -0800, Ian Rogers 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@google.com>

Applied to perf-tools-next, thanks!

Best regards,
Namhyung