diff mbox series

[v2] perf_event_open.2: update the man page with CAP_PERFMON related information

Message ID 33c10554-c0ee-9e46-2946-67a9deac6752@linux.intel.com
State New
Headers show
Series [v2] perf_event_open.2: update the man page with CAP_PERFMON related information | expand

Commit Message

Alexey Budankov Oct. 27, 2020, 4:48 p.m. UTC
Extend perf_event_open 2 man page with the information about
CAP_PERFMON capability designed to secure performance monitoring
and observability operation in a system according to the principle
of least privilege [1] (POSIX IEEE 1003.1e, 2.2.2.39).

[1] https://sites.google.com/site/fullycapable/, posix_1003.1e-990310.pdf

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 man2/perf_event_open.2 | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

Comments

Michael Kerrisk (man-pages) Oct. 27, 2020, 4:57 p.m. UTC | #1
Hello Alexey,

On 10/27/20 5:48 PM, Alexey Budankov wrote:
> 
> Extend perf_event_open 2 man page with the information about
> CAP_PERFMON capability designed to secure performance monitoring
> and observability operation in a system according to the principle
> of least privilege [1] (POSIX IEEE 1003.1e, 2.2.2.39).
> 
> [1] https://sites.google.com/site/fullycapable/, posix_1003.1e-990310.pdf
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>

Thanks for this. I've applied. I have a few questions/comments below.

> ---
>  man2/perf_event_open.2 | 32 ++++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
> index 4827a359d..9810bc554 100644
> --- a/man2/perf_event_open.2
> +++ b/man2/perf_event_open.2
> @@ -97,6 +97,8 @@ when running on the specified CPU.
>  .BR "pid == \-1" " and " "cpu >= 0"
>  This measures all processes/threads on the specified CPU.
>  This requires
> +.B CAP_PERFMON
> +(since Linux 5.8) or
>  .B CAP_SYS_ADMIN
>  capability or a
>  .I /proc/sys/kernel/perf_event_paranoid
> @@ -108,9 +110,11 @@ This setting is invalid and will return an error.
>  When
>  .I pid
>  is greater than zero, permission to perform this system call
> -is governed by a ptrace access mode
> +is governed by
> +.B CAP_PERFMON
> +(since Linux 5.9) and a ptrace access mode

I want to check: did you really mean 5.9 here? (Everywhere else,
5.8 is mentioned, but perhaps this change came in the next kernel 
version.)

>  .B PTRACE_MODE_READ_REALCREDS
> -check; see
> +check on older Linux versions; see
>  .BR ptrace (2).
>  .PP
>  The
> @@ -2925,6 +2929,8 @@ to hold the result.
>  This allows attaching a Berkeley Packet Filter (BPF)
>  program to an existing kprobe tracepoint event.
>  You need
> +.B CAP_PERFMON
> +(since Linux 5.8) or
>  .B CAP_SYS_ADMIN
>  privileges to use this ioctl.
>  .IP
> @@ -2967,6 +2973,8 @@ have multiple events attached to a tracepoint.
>  Querying this value on one tracepoint event returns the id
>  of all BPF programs in all events attached to the tracepoint.
>  You need
> +.B CAP_PERFMON
> +(since Linux 5.8) or
>  .B CAP_SYS_ADMIN
>  privileges to use this ioctl.
>  .IP
> @@ -3175,6 +3183,8 @@ it was expecting.
>  .TP
>  .B EACCES
>  Returned when the requested event requires
> +.B CAP_PERFMON
> +(since Linux 5.8) or
>  .B CAP_SYS_ADMIN
>  permissions (or a more permissive perf_event paranoid setting).
>  Some common cases where an unprivileged process
> @@ -3296,6 +3306,8 @@ setting is specified.
>  It can also happen, as with
>  .BR EACCES ,
>  when the requested event requires
> +.B CAP_PERFMON
> +(since Linux 5.8) or
>  .B CAP_SYS_ADMIN
>  permissions (or a more permissive perf_event paranoid setting).
>  This includes setting a breakpoint on a kernel address,
> @@ -3326,6 +3338,22 @@ The official way of knowing if
>  support is enabled is checking
>  for the existence of the file
>  .IR /proc/sys/kernel/perf_event_paranoid .
> +.PP
> +.B CAP_PERFMON
> +capability (since Linux 5.8) provides secure approach to
> +performance monitoring and observability operations in a system
> +according to the principal of least privilege (POSIX IEEE 1003.1e).
> +Accessing system performance monitoring and observability operations
> +using
> +.B CAP_PERFMON
> +rather than the much more powerful
> +.B CAP_SYS_ADMIN
> +excludes chances to misuse credentials and makes operations more secure.
> +.B CAP_SYS_ADMIN
> +usage for secure system performance monitoring and observability
> +is discouraged with respect to
> +.B CAP_PERFMON
> +capability.

Thank you for adding the above piece. That point of course
really needs to be emphasized!

Thanks,

Michael
Alexey Budankov Oct. 27, 2020, 5:10 p.m. UTC | #2
On 27.10.2020 19:57, Michael Kerrisk (man-pages) wrote:
> Hello Alexey,
> 
> On 10/27/20 5:48 PM, Alexey Budankov wrote:
>>
>> Extend perf_event_open 2 man page with the information about
>> CAP_PERFMON capability designed to secure performance monitoring
>> and observability operation in a system according to the principle
>> of least privilege [1] (POSIX IEEE 1003.1e, 2.2.2.39).
>>
>> [1] https://sites.google.com/site/fullycapable/, posix_1003.1e-990310.pdf
>>
>> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> 
> Thanks for this. I've applied. I have a few questions/comments below.
> 
>> ---
>>  man2/perf_event_open.2 | 32 ++++++++++++++++++++++++++++++--
>>  1 file changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
>> index 4827a359d..9810bc554 100644
>> --- a/man2/perf_event_open.2
>> +++ b/man2/perf_event_open.2
>> @@ -97,6 +97,8 @@ when running on the specified CPU.
>>  .BR "pid == \-1" " and " "cpu >= 0"
>>  This measures all processes/threads on the specified CPU.
>>  This requires
>> +.B CAP_PERFMON
>> +(since Linux 5.8) or
>>  .B CAP_SYS_ADMIN
>>  capability or a
>>  .I /proc/sys/kernel/perf_event_paranoid
>> @@ -108,9 +110,11 @@ This setting is invalid and will return an error.
>>  When
>>  .I pid
>>  is greater than zero, permission to perform this system call
>> -is governed by a ptrace access mode
>> +is governed by
>> +.B CAP_PERFMON
>> +(since Linux 5.9) and a ptrace access mode
> 
> I want to check: did you really mean 5.9 here? (Everywhere else,
> 5.8 is mentioned, but perhaps this change came in the next kernel 
> version.)

Yes, it is not a typo. This thing was merged into v5.9.

Thanks,
Alexei

> 
>>  .B PTRACE_MODE_READ_REALCREDS
>> -check; see
>> +check on older Linux versions; see
>>  .BR ptrace (2).
>>  .PP
>>  The
>> @@ -2925,6 +2929,8 @@ to hold the result.
>>  This allows attaching a Berkeley Packet Filter (BPF)
>>  program to an existing kprobe tracepoint event.
>>  You need
>> +.B CAP_PERFMON
>> +(since Linux 5.8) or
>>  .B CAP_SYS_ADMIN
>>  privileges to use this ioctl.
>>  .IP
>> @@ -2967,6 +2973,8 @@ have multiple events attached to a tracepoint.
>>  Querying this value on one tracepoint event returns the id
>>  of all BPF programs in all events attached to the tracepoint.
>>  You need
>> +.B CAP_PERFMON
>> +(since Linux 5.8) or
>>  .B CAP_SYS_ADMIN
>>  privileges to use this ioctl.
>>  .IP
>> @@ -3175,6 +3183,8 @@ it was expecting.
>>  .TP
>>  .B EACCES
>>  Returned when the requested event requires
>> +.B CAP_PERFMON
>> +(since Linux 5.8) or
>>  .B CAP_SYS_ADMIN
>>  permissions (or a more permissive perf_event paranoid setting).
>>  Some common cases where an unprivileged process
>> @@ -3296,6 +3306,8 @@ setting is specified.
>>  It can also happen, as with
>>  .BR EACCES ,
>>  when the requested event requires
>> +.B CAP_PERFMON
>> +(since Linux 5.8) or
>>  .B CAP_SYS_ADMIN
>>  permissions (or a more permissive perf_event paranoid setting).
>>  This includes setting a breakpoint on a kernel address,
>> @@ -3326,6 +3338,22 @@ The official way of knowing if
>>  support is enabled is checking
>>  for the existence of the file
>>  .IR /proc/sys/kernel/perf_event_paranoid .
>> +.PP
>> +.B CAP_PERFMON
>> +capability (since Linux 5.8) provides secure approach to
>> +performance monitoring and observability operations in a system
>> +according to the principal of least privilege (POSIX IEEE 1003.1e).
>> +Accessing system performance monitoring and observability operations
>> +using
>> +.B CAP_PERFMON
>> +rather than the much more powerful
>> +.B CAP_SYS_ADMIN
>> +excludes chances to misuse credentials and makes operations more secure.
>> +.B CAP_SYS_ADMIN
>> +usage for secure system performance monitoring and observability
>> +is discouraged with respect to
>> +.B CAP_PERFMON
>> +capability.
> 
> Thank you for adding the above piece. That point of course
> really needs to be emphasized!
> 
> Thanks,
> 
> Michael
> 
>
Michael Kerrisk (man-pages) Oct. 27, 2020, 5:11 p.m. UTC | #3
On Tue, 27 Oct 2020 at 18:10, Alexey Budankov
<alexey.budankov@linux.intel.com> wrote:
>
>
> On 27.10.2020 19:57, Michael Kerrisk (man-pages) wrote:
> > Hello Alexey,
> >
> > On 10/27/20 5:48 PM, Alexey Budankov wrote:
> >>
> >> Extend perf_event_open 2 man page with the information about
> >> CAP_PERFMON capability designed to secure performance monitoring
> >> and observability operation in a system according to the principle
> >> of least privilege [1] (POSIX IEEE 1003.1e, 2.2.2.39).
> >>
> >> [1] https://sites.google.com/site/fullycapable/, posix_1003.1e-990310.pdf
> >>
> >> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> >
> > Thanks for this. I've applied. I have a few questions/comments below.
> >
> >> ---
> >>  man2/perf_event_open.2 | 32 ++++++++++++++++++++++++++++++--
> >>  1 file changed, 30 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
> >> index 4827a359d..9810bc554 100644
> >> --- a/man2/perf_event_open.2
> >> +++ b/man2/perf_event_open.2
> >> @@ -97,6 +97,8 @@ when running on the specified CPU.
> >>  .BR "pid == \-1" " and " "cpu >= 0"
> >>  This measures all processes/threads on the specified CPU.
> >>  This requires
> >> +.B CAP_PERFMON
> >> +(since Linux 5.8) or
> >>  .B CAP_SYS_ADMIN
> >>  capability or a
> >>  .I /proc/sys/kernel/perf_event_paranoid
> >> @@ -108,9 +110,11 @@ This setting is invalid and will return an error.
> >>  When
> >>  .I pid
> >>  is greater than zero, permission to perform this system call
> >> -is governed by a ptrace access mode
> >> +is governed by
> >> +.B CAP_PERFMON
> >> +(since Linux 5.9) and a ptrace access mode
> >
> > I want to check: did you really mean 5.9 here? (Everywhere else,
> > 5.8 is mentioned, but perhaps this change came in the next kernel
> > version.)
>
> Yes, it is not a typo. This thing was merged into v5.9.
>
> Thanks,
> Alexei

Thanks, Alexei!
diff mbox series

Patch

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index 4827a359d..9810bc554 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -97,6 +97,8 @@  when running on the specified CPU.
 .BR "pid == \-1" " and " "cpu >= 0"
 This measures all processes/threads on the specified CPU.
 This requires
+.B CAP_PERFMON
+(since Linux 5.8) or
 .B CAP_SYS_ADMIN
 capability or a
 .I /proc/sys/kernel/perf_event_paranoid
@@ -108,9 +110,11 @@  This setting is invalid and will return an error.
 When
 .I pid
 is greater than zero, permission to perform this system call
-is governed by a ptrace access mode
+is governed by
+.B CAP_PERFMON
+(since Linux 5.9) and a ptrace access mode
 .B PTRACE_MODE_READ_REALCREDS
-check; see
+check on older Linux versions; see
 .BR ptrace (2).
 .PP
 The
@@ -2925,6 +2929,8 @@  to hold the result.
 This allows attaching a Berkeley Packet Filter (BPF)
 program to an existing kprobe tracepoint event.
 You need
+.B CAP_PERFMON
+(since Linux 5.8) or
 .B CAP_SYS_ADMIN
 privileges to use this ioctl.
 .IP
@@ -2967,6 +2973,8 @@  have multiple events attached to a tracepoint.
 Querying this value on one tracepoint event returns the id
 of all BPF programs in all events attached to the tracepoint.
 You need
+.B CAP_PERFMON
+(since Linux 5.8) or
 .B CAP_SYS_ADMIN
 privileges to use this ioctl.
 .IP
@@ -3175,6 +3183,8 @@  it was expecting.
 .TP
 .B EACCES
 Returned when the requested event requires
+.B CAP_PERFMON
+(since Linux 5.8) or
 .B CAP_SYS_ADMIN
 permissions (or a more permissive perf_event paranoid setting).
 Some common cases where an unprivileged process
@@ -3296,6 +3306,8 @@  setting is specified.
 It can also happen, as with
 .BR EACCES ,
 when the requested event requires
+.B CAP_PERFMON
+(since Linux 5.8) or
 .B CAP_SYS_ADMIN
 permissions (or a more permissive perf_event paranoid setting).
 This includes setting a breakpoint on a kernel address,
@@ -3326,6 +3338,22 @@  The official way of knowing if
 support is enabled is checking
 for the existence of the file
 .IR /proc/sys/kernel/perf_event_paranoid .
+.PP
+.B CAP_PERFMON
+capability (since Linux 5.8) provides secure approach to
+performance monitoring and observability operations in a system
+according to the principal of least privilege (POSIX IEEE 1003.1e).
+Accessing system performance monitoring and observability operations
+using
+.B CAP_PERFMON
+rather than the much more powerful
+.B CAP_SYS_ADMIN
+excludes chances to misuse credentials and makes operations more secure.
+.B CAP_SYS_ADMIN
+usage for secure system performance monitoring and observability
+is discouraged with respect to
+.B CAP_PERFMON
+capability.
 .SH BUGS
 The
 .B F_SETOWN_EX