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

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

[Li Zhang]

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@linux.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

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

[Arnaldo Carvalho de Melo]

Em Fri, Jun 26, 2015 at 02:22:29PM +0800, Li Zhang escreveu:
> ping ?

Thanks, applied.

- Arnaldo

[tip:perf/urgent] perf symbols: Check access permission when reading symbol files

[tip-bot for Li Zhang]

Commit-ID:  36c8bb56a9f718a9a5f35d1834ca9dcec95deb4a
Gitweb:     http://git.kernel.org/tip/36c8bb56a9f718a9a5f35d1834ca9dcec95deb4a
Author:     Li Zhang <zhlcindy@linux.vnet.ibm.com>
AuthorDate: Fri, 19 Jun 2015 16:57:33 +0800
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 26 Jun 2015 12:11:53 -0300

perf symbols: Check access permission when reading symbol files

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@linux.vnet.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1434704253-2632-1-git-send-email-zhlcindy@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 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 32626ea..348bed4 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -742,6 +742,17 @@ 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 504f2d7..48b588c 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1132,8 +1132,11 @@ 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,