Re: [PATCH 2/4] tracing/user_events: Validate explicit struct field sizes

[Steven Rostedt]

Beau,

Can you review this?

Thanks,

-- Steve


On Wed, 22 Jul 2026 14:10:38 +0800
Li Qiang <liqiang01@xxxxxxxxxx> wrote:

> User event declarations permit an explicit size for a struct field. The
> parser accumulated that size in an unsigned offset, then assigned the
> parsed unsigned value directly to signed field metadata. Oversized
> declarations or cumulative offsets could wrap or become invalid signed
> values.
> 
> Validate an explicit size is representable as int before storing it. Keep
> the running offset signed and reject additions exceeding INT_MAX, so
> invalid field layouts are rejected during declaration parsing.
> 
> Fixes: 7f5a08c79df3 ("user_events: Add minimal support for trace_event into ftrace")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Li Qiang <liqiang01@xxxxxxxxxx>
> ---
>  kernel/trace/trace_events_user.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 8c82ecb735f4..fd5b3946921c 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -1197,10 +1197,12 @@ static int user_event_add_field(struct user_event *user, const char *type,
>   * Format: type name [size]
>   */
>  static int user_event_parse_field(char *field, struct user_event *user,
> -				  u32 *offset)
> +				  int *offset)
>  {
>  	char *part, *type, *name;
> -	u32 depth = 0, saved_offset = *offset;
> +	u32 depth = 0;
> +	unsigned int field_size;
> +	int saved_offset = *offset;
>  	int len, size = -EINVAL;
>  	bool is_struct = false;
>  
> @@ -1261,8 +1263,11 @@ static int user_event_parse_field(char *field, struct user_event *user,
>  			if (!is_struct)
>  				return -EINVAL;
>  
> -			if (kstrtou32(part, 10, &size))
> +			if (kstrtouint(part, 10, &field_size))
>  				return -EINVAL;
> +			if (field_size > INT_MAX)
> +				return -E2BIG;
> +			size = field_size;
>  			break;
>  		default:
>  			return -EINVAL;
> @@ -1281,6 +1286,9 @@ static int user_event_parse_field(char *field, struct user_event *user,
>  	if (size < 0)
>  		return size;
>  
> +	if (size > INT_MAX - saved_offset)
> +		return -E2BIG;
> +
>  	*offset = saved_offset + size;
>  
>  	return user_event_add_field(user, type, name, saved_offset, size,
> @@ -1290,7 +1298,7 @@ static int user_event_parse_field(char *field, struct user_event *user,
>  static int user_event_parse_fields(struct user_event *user, char *args)
>  {
>  	char *field;
> -	u32 offset = sizeof(struct trace_entry);
> +	int offset = sizeof(struct trace_entry);
>  	int ret = -EINVAL;
>  
>  	if (args == NULL)