* Re: [PATCH 1/1] perf tools: Check access permission when reading /proc/kcore file.
[not found] <1433905293-16176-1-git-send-email-zhlcindy@linux.vnet.ibm.com>
@ 2015-06-10 14:44 ` Arnaldo Carvalho de Melo
2015-06-15 2:24 ` Li Zhang
0 siblings, 1 reply; 2+ messages in thread
From: Arnaldo Carvalho de Melo @ 2015-06-10 14:44 UTC (permalink / raw)
To: Li Zhang; +Cc: mingo, sukadev, linux-kernel
Em Wed, Jun 10, 2015 at 11:01:33AM +0800, Li Zhang escreveu:
> 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.
> It needs to change access permission to allow a specific user to read
> /proc/kcore or use root to execute the perf command.
But then only if the user tries it again, using -v to enable verbose
mode is that the message will be presented, how about instead return
-EPERM, or -errno, so that this error is propagated back and we
eventually emit a more meaningful message to the user, such as:
"Insufficient permission to access %s.", kcore_filename
Trying to check if that is possible by going to the dso__load_kcore()
callers and on back to the tools.
- Arnaldo
> This patch is to check access permission when reading kcore file.
>
> Signed-off-by: Li Zhang <zhlcindy@linux.vnet.ibm.com>
> ---
> tools/perf/util/symbol.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 201f6c4c..8255556 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1125,6 +1125,11 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
> md.type = map->type;
> INIT_LIST_HEAD(&md.maps);
>
> + if (access(kcore_filename, R_OK)) {
> + pr_debug("Can't access file %s.\n", kcore_filename);
> + return -EINVAL;
> + }
> +
> fd = open(kcore_filename, O_RDONLY);
> if (fd < 0)
> return -EINVAL;
> --
> 2.1.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH 1/1] perf tools: Check access permission when reading /proc/kcore file.
2015-06-10 14:44 ` [PATCH 1/1] perf tools: Check access permission when reading /proc/kcore file Arnaldo Carvalho de Melo
@ 2015-06-15 2:24 ` Li Zhang
0 siblings, 0 replies; 2+ messages in thread
From: Li Zhang @ 2015-06-15 2:24 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo; +Cc: mingo, sukadev, linux-kernel
On 2015年06月10日 22:44, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jun 10, 2015 at 11:01:33AM +0800, Li Zhang escreveu:
>> 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.
>> It needs to change access permission to allow a specific user to read
>> /proc/kcore or use root to execute the perf command.
> But then only if the user tries it again, using -v to enable verbose
> mode is that the message will be presented, how about instead return
> -EPERM, or -errno, so that this error is propagated back and we
> eventually emit a more meaningful message to the user, such as:
>
> "Insufficient permission to access %s.", kcore_filename
>
> Trying to check if that is possible by going to the dso__load_kcore()
> callers and on back to the tools.
This sounds much better. I will check whether it can deliver this
message to user.
Thanks Li
>
> - Arnaldo
>
>> This patch is to check access permission when reading kcore file.
>>
>> Signed-off-by: Li Zhang <zhlcindy@linux.vnet.ibm.com>
>> ---
>> tools/perf/util/symbol.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
>> index 201f6c4c..8255556 100644
>> --- a/tools/perf/util/symbol.c
>> +++ b/tools/perf/util/symbol.c
>> @@ -1125,6 +1125,11 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
>> md.type = map->type;
>> INIT_LIST_HEAD(&md.maps);
>>
>> + if (access(kcore_filename, R_OK)) {
>> + pr_debug("Can't access file %s.\n", kcore_filename);
>> + return -EINVAL;
>> + }
>> +
>> fd = open(kcore_filename, O_RDONLY);
>> if (fd < 0)
>> return -EINVAL;
>> --
>> 2.1.0
> --
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--
Li Zhang
IBM China Linux Technology Centre
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2015-06-10 14:44 ` [PATCH 1/1] perf tools: Check access permission when reading /proc/kcore file Arnaldo Carvalho de Melo
2015-06-15 2:24 ` Li Zhang
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