linux-kernel - Re: [PATCH v3 1/1] perf tools: Check access permission when reading symbol files

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Date:	Fri, 26 Jun 2015 14:22:29 +0800
From:	Li Zhang <zhlcindy@...ux.vnet.ibm.com>
To:	Li Zhang <zhlcindy@...ux.vnet.ibm.com>
CC:	acme@...nel.org, mingo@...hat.com, sukadev@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] perf tools: Check access permission when reading
 symbol files

ping ?

On 2015年06月19日 16:57, Li Zhang wrote:
> There 2 problems when reading symbols files:
>
> *  It doesn't report any errors even if when users specify symbol
>     files which don't exist with --kallsyms or --vmlinux. The result
>     just shows the address without symbols, which is not what is expected.
>     So it's better to report errors and exit the program.
>
> *  When using command perf report --kallsyms=/proc/kallsyms with a
>     non-root user, symbols are resolved. Then select one symbol and
>     annotate it, it reports the error as the following:
>     Can't annotate __clear_user: No vmlinux file with build id xxx was
>     found.
>
>     The problem is caused by reading /proc/kcore without access permission.
>     /proc/kcore requires CAP_SYS_RAWIO capability to access, so it needs to
>     change access permission to allow a specific user to read /proc/kcore or
>     use root to execute the perf command.
>
> This patch is to report errors when symbol files specified by users
> don't exist. And check access permission of /proc/kcore when reading it.
>
> Signed-off-by: Li Zhang <zhlcindy@...ux.vnet.ibm.com>
> ---
>
> v3 -> v2:
>    * Add checking symbol files when user specify these files.
>    * Report an error to users when open fails. Suggested by Sukar
>
> v2 -> v1:
>    * Report one useful message to users about the access permision,
>      then go back to the tools. Suggested by Arnaldo Carvalho de Melo.
>
>   tools/perf/builtin-report.c | 11 +++++++++++
>   tools/perf/util/symbol.c    |  5 ++++-
>   2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> index 476cdf7..1c353b1 100644
> --- a/tools/perf/builtin-report.c
> +++ b/tools/perf/builtin-report.c
> @@ -731,6 +731,17 @@ int cmd_report(int argc, const char **argv, const char *prefix __maybe_unused)
>
>   	argc = parse_options(argc, argv, options, report_usage, 0);
>
> +	if (symbol_conf.vmlinux_name &&
> +		access(symbol_conf.vmlinux_name, R_OK)) {
> +		pr_err("Invalid file: %s\n", symbol_conf.vmlinux_name);
> +		return -EINVAL;
> +	}
> +	if (symbol_conf.kallsyms_name &&
> +		access(symbol_conf.kallsyms_name, R_OK)) {
> +		pr_err("Invalid file: %s\n", symbol_conf.kallsyms_name);
> +		return -EINVAL;
> +	}
> +
>   	if (report.use_stdio)
>   		use_browser = 0;
>   	else if (report.use_tui)
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 201f6c4c..46aa93d 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1126,8 +1126,11 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
>   	INIT_LIST_HEAD(&md.maps);
>
>   	fd = open(kcore_filename, O_RDONLY);
> -	if (fd < 0)
> +	if (fd < 0) {
> +		pr_err("%s requires CAP_SYS_RAWIO capability to access.\n",
> +			kcore_filename);
>   		return -EINVAL;
> +	}
>
>   	/* Read new maps into temporary lists */
>   	err = file__read_maps(fd, md.type == MAP__FUNCTION, kcore_mapfn, &md,


-- 

Li Zhang
IBM China Linux Technology Centre

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