Re: [PATCH 10/12] perf jitdump: Validate debug entries on native (non-swap) path

[Ian Rogers]

On Wed, Aug 5, 2026 at 6:32 AM Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>
> From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> The bounds-checking and nr_entry clamping added for the byte-swap path
> only runs when jd->needs_bswap is true.  On native-endian files, nr_entry
> passes through unvalidated to jit_repipe_debug_info(), which stores it
> as jd->nr_debug_entries.  Downstream, jit_process_debug_info() in
> genelf_debug.c iterates nr_debug_entries times via debug_entry_next(),
> which calls strlen() on each entry's name field — a crafted nr_entry
> causes OOB reads and writes.
>
> Add bounds-checked iteration in jit_repipe_debug_info() that validates
> each debug_entry fits in the payload and its name is NUL-terminated
> before calling debug_entry_next().  Clamp nr_debug_entries to the count
> of valid entries.
>
> Fixes: 598b7c6919c7bbcc ("perf jit: add source line info support")
> Reported-by: sashiko-bot <sashiko-bot@xxxxxxxxxx>
> Cc: Stephane Eranian <eranian@xxxxxxxxxx>
> Assisted-by: Claude:claude-opus-4.6
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks!
Ian

> ---
>  tools/perf/util/jitdump.c | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
> index 02840dbf8a1fc16c..87612ef3e232598e 100644
> --- a/tools/perf/util/jitdump.c
> +++ b/tools/perf/util/jitdump.c
> @@ -694,8 +694,10 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
>
>  static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
>  {
> -       void *data;
> -       size_t sz;
> +       struct debug_entry *ent;
> +       void *data, *end;
> +       size_t sz, valid;
> +       uint64_t i;
>
>         if (!(jd && jr))
>                 return -1;
> @@ -715,10 +717,25 @@ static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
>         jd->debug_data       = data;
>
>         /*
> -        * we must use nr_entry instead of size here because
> -        * we cannot distinguish actual entry from padding otherwise
> +        * Clamp nr_debug_entries to entries that actually fit in the
> +        * payload.  The byte-swap path already does this for cross-endian
> +        * files; validate on the native path too, since downstream
> +        * jit_process_debug_info() iterates via debug_entry_next() which
> +        * calls strlen() on each entry's name field.
>          */
> -       jd->nr_debug_entries = jr->info.nr_entry;
> +       end = data + sz;
> +       ent = data;
> +       valid = 0;
> +       for (i = 0; i < jr->info.nr_entry; i++) {
> +               if ((void *)ent + sizeof(*ent) > end)
> +                       break;
> +               /* name must be NUL-terminated within the payload */
> +               if (!memchr(ent->name, '\0', (char *)end - ent->name))
> +                       break;
> +               ent = debug_entry_next(ent);
> +               valid++;
> +       }
> +       jd->nr_debug_entries = valid;
>
>         return 0;
>  }
> --
> 2.55.0
>