Re: [PATCH 03/12] perf jitdump: Prevent integer underflow in debug info size calculation

[Ian Rogers]

On Wed, Aug 5, 2026 at 6:31 AM Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>
> From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> jit_repipe_debug_info() and jit_repipe_unwinding_info() compute payload
> sizes by subtracting the fixed header size from total_size:
>
>   sz = jr->prefix.total_size - sizeof(jr->info);
>
> When total_size is smaller than the header struct (from a truncated or
> corrupted jitdump record), the subtraction underflows to a massive
> value, causing an oversized allocation followed by an OOB memcpy.
>
> Validate that total_size covers at least the fixed header before the
> subtraction in both functions.
>
> Fixes: 598b7c6919c7 ("perf jit: add source line info support")
> Fixes: 0284fecd13b6 ("perf jit: Add unwinding support")
> Reported-by: sashiko-bot <sashiko-bot@xxxxxxxxxx>
> Cc: Stephane Eranian <eranian@xxxxxxxxxx>
> Cc: Stefano Sanfilippo <ssanfilippo@xxxxxxxxxxxx>
> 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 | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
> index 3195f94187164066..787f8a03dae87908 100644
> --- a/tools/perf/util/jitdump.c
> +++ b/tools/perf/util/jitdump.c
> @@ -669,6 +669,10 @@ static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
>         if (!(jd && jr))
>                 return -1;
>
> +       /* total_size must cover at least the fixed header */
> +       if (jr->prefix.total_size < sizeof(jr->info))
> +               return -1;
> +
>         sz  = jr->prefix.total_size - sizeof(jr->info);
>         data = malloc(sz);
>         if (!data)
> @@ -696,6 +700,10 @@ jit_repipe_unwinding_info(struct jit_buf_desc *jd, union jr_entry *jr)
>         if (!(jd && jr))
>                 return -1;
>
> +       /* total_size must cover at least the fixed header */
> +       if (jr->prefix.total_size < sizeof(jr->unwinding))
> +               return -1;
> +
>         unwinding_data_size  = jr->prefix.total_size - sizeof(jr->unwinding);
>         unwinding_data = malloc(unwinding_data_size);
>         if (!unwinding_data)
> --
> 2.55.0
>