Hi Masami,

On Thu, Feb 22, 2018 at 04:45:01PM +0900, Masami Hiramatsu wrote:
> In Documentation/trace/kprobetrace.txt, it says
> 
>  @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
> 
> However, the parser doesn't parse minus offset correctly, since
> commit 2fba0c8867af ("tracing/kprobes: Fix probe offset to be
> unsigned") drops minus ("-") offset support for kprobe probe
> address usage.
> 
> This fixes the traceprobe_split_symbol_offset() to parse minus
> offset again with checking the offset range, and add a minus
> offset check in kprobe probe address usage.
> 
> Fixes: 2fba0c8867af ("tracing/kprobes: Fix probe offset to be unsigned")
> Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
> ---
>  Changes in v2.1:
>   - Fix to ensure the offset value is less than LONG_MAX.
>   - Fail if the offset is minus when traceprobe_split_symbol_offset()
>     is used for the probe address.
>   - Add Fixes tag.
> ---
>  kernel/trace/trace_kprobe.c |    4 ++--
>  kernel/trace/trace_probe.c  |   15 ++++++++++-----
>  kernel/trace/trace_probe.h  |    2 +-
>  3 files changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 5ce9b8cf7be3..b5b1d8aa47d6 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -667,7 +667,7 @@ static int create_trace_kprobe(int argc, char **argv)
>       char *symbol = NULL, *event = NULL, *group = NULL;
>       int maxactive = 0;
>       char *arg;
> -     unsigned long offset = 0;
> +     long offset = 0;
>       void *addr = NULL;
>       char buf[MAX_EVENT_NAME_LEN];
>  
> @@ -755,7 +755,7 @@ static int create_trace_kprobe(int argc, char **argv)
>               symbol = argv[1];
>               /* TODO: support .init module functions */
>               ret = traceprobe_split_symbol_offset(symbol, &offset);
> -             if (ret) {
> +             if (ret || offset < 0) {
>                       pr_info("Failed to parse either an address or a 
> symbol.\n");
>                       return ret;
>               }
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index d59357308677..ec3856147fdd 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -320,21 +320,26 @@ static fetch_func_t get_fetch_size_function(const 
> struct fetch_type *type,
>  }
>  
>  /* Split symbol and offset. */
> -int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
> +int traceprobe_split_symbol_offset(char *symbol, long *offset)
>  {
> +     unsigned long ul;
>       char *tmp;
>       int ret;
>  
>       if (!offset)
>               return -EINVAL;
>  
> -     tmp = strchr(symbol, '+');
> +     tmp = strpbrk(symbol, "+-");
>       if (tmp) {
> -             /* skip sign because kstrtoul doesn't accept '+' */
> -             ret = kstrtoul(tmp + 1, 0, offset);
> +             ret = kstrtoul(tmp + 1, 0, &ul);

Why not just using kstrtol() which handles the sign correctly?

Thanks,
Namhyung


>               if (ret)
>                       return ret;
> -
> +             if (ul > LONG_MAX)
> +                     return -E2BIG;
> +             if (*tmp == '-')
> +                     *offset = -ul;
> +             else
> +                     *offset = ul;
>               *tmp = '\0';
>       } else
>               *offset = 0;
> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> index 0745f895f780..75daff22ccea 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -365,7 +365,7 @@ extern int traceprobe_conflict_field_name(const char 
> *name,
>  extern void traceprobe_update_arg(struct probe_arg *arg);
>  extern void traceprobe_free_probe_arg(struct probe_arg *arg);
>  
> -extern int traceprobe_split_symbol_offset(char *symbol, unsigned long 
> *offset);
> +extern int traceprobe_split_symbol_offset(char *symbol, long *offset);
>  
>  /* Sum up total data length for dynamic arraies (strings) */
>  static nokprobe_inline int
> 

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