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* [PATCH v2 00/11] Introduce Simple atomic counters
@ 2020-10-06 20:44 Shuah Khan
  2020-10-06 20:44 ` [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32 Shuah Khan
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Shuah Khan @ 2020-10-06 20:44 UTC (permalink / raw)
  To: corbet, keescook, gregkh, shuah, rafael, johannes, lenb,
	james.morse, tony.luck, bp, arve, tkjos, maco, joel, christian,
	hridya, surenb, minyard, arnd, mchehab, rric
  Cc: Shuah Khan, linux-doc, linux-kernel, linux-kselftest, linux-acpi,
	devel, openipmi-developer, linux-edac

This patch series is a result of discussion at the refcount_t BOF
the Linux Plumbers Conference. In this discussion, we identified
a need for looking closely and investigating atomic_t usages in
the kernel when it is used strictly as a counter without it
controlling object lifetimes and state changes.

There are a number of atomic_t usages in the kernel where atomic_t api
is used strictly for counting and not for managing object lifetime. In
some cases, atomic_t might not even be needed.

The purpose of these counters is to clearly differentiate atomic_t
counters from atomic_t usages that guard object lifetimes, hence prone
to overflow and underflow errors. It allows tools that scan for underflow
and overflow on atomic_t usages to detect overflow and underflows to scan
just the cases that are prone to errors.

Simple atomic counters api provides interfaces for simple atomic counters
that just count, and don't guard resource lifetimes. Counter will wrap
around to 0 when it overflows and should not be used to guard resource
lifetimes, device usage and open counts that control state changes, and
pm states.

Using counter_atomic* to guard lifetimes could lead to use-after free
when it overflows and undefined behavior when used to manage state
changes and device usage/open states.

This patch series introduces Simple atomic counters. Counter atomic ops
leverage atomic_t and provide a sub-set of atomic_t ops.

In addition this patch series converts a few drivers to use the new api.
The following criteria is used for select variables for conversion:

1. Variable doesn't guard object lifetimes, manage state changes e.g:
   device usage counts, device open counts, and pm states.
2. Variable is used for stats and counters.
3. The conversion doesn't change the overflow behavior.

Changes since Patch v1
-- Thanks for reviews and reviewed-by, and Acked-by tags. Updated
   the patches with the tags.
-- Addressed Kees's  and Joel's comments:
   1. Removed dec_return interfaces (Patch 1/11)
   2. Removed counter_simple interfaces to be added later with changes
      to drivers that use them (if any) (Patch 1/11)
   3. Comment and Changelogs updates to Patch 2/11

Kees, if this series is good, would you like to take this through your
tree or would you like to take this through mine?

Changes since RFC:
-- Thanks for reviews and reviewed-by, and Acked-by tags. Updated
   the patches with the tags.
-- Addressed Kees's comments:
   1. Non-atomic counters renamed to counter_simple32 and counter_simple64
      to clearly indicate size.
   2. Added warning for counter_simple* usage and it should be used only
      when there is no need for atomicity.
   3. Renamed counter_atomic to counter_atomic32 to clearly indicate size.
   4. Renamed counter_atomic_long to counter_atomic64 and it now uses
      atomic64_t ops and indicates size.
   5. Test updated for the API renames.
   6. Added helper functions for test results printing
   7. Verified that the test module compiles in kunit env. and test
      module can be loaded to run the test.
   8. Updated Documentation to reflect the intent to make the API
      restricted so it can never be used to guard object lifetimes
      and state management. I left _return ops for now, inc_return
      is necessary for now as per the discussion we had on this topic.
-- Updated driver patches with API name changes.
-- We discussed if binder counters can be non-atomic. For now I left
   them the same as the RFC patch - using counter_atomic32
-- Unrelated to this patch series:
   The patch series review uncovered improvements could be made to
   test_async_driver_probe and vmw_vmci/vmci_guest. I will track
   these for fixing later.

Shuah Khan (11):
  counters: Introduce counter_atomic* counters
  selftests:lib:test_counters: add new test for counters
  drivers/base: convert deferred_trigger_count and probe_count to
    counter_atomic32
  drivers/base/devcoredump: convert devcd_count to counter_atomic32
  drivers/acpi: convert seqno counter_atomic32
  drivers/acpi/apei: convert seqno counter_atomic32
  drivers/android/binder: convert stats, transaction_log to
    counter_atomic32
  drivers/base/test/test_async_driver_probe: convert to use
    counter_atomic32
  drivers/char/ipmi: convert stats to use counter_atomic32
  drivers/misc/vmw_vmci: convert num guest devices counter to
    counter_atomic32
  drivers/edac: convert pci counters to counter_atomic32

 Documentation/core-api/counters.rst          | 103 +++++++++++
 MAINTAINERS                                  |   8 +
 drivers/acpi/acpi_extlog.c                   |   5 +-
 drivers/acpi/apei/ghes.c                     |   5 +-
 drivers/android/binder.c                     |  41 ++---
 drivers/android/binder_internal.h            |   3 +-
 drivers/base/dd.c                            |  19 +-
 drivers/base/devcoredump.c                   |   5 +-
 drivers/base/test/test_async_driver_probe.c  |  23 +--
 drivers/char/ipmi/ipmi_msghandler.c          |   9 +-
 drivers/char/ipmi/ipmi_si_intf.c             |   9 +-
 drivers/edac/edac_pci.h                      |   5 +-
 drivers/edac/edac_pci_sysfs.c                |  28 +--
 drivers/misc/vmw_vmci/vmci_guest.c           |   9 +-
 include/linux/counters.h                     | 173 +++++++++++++++++++
 lib/Kconfig                                  |  10 ++
 lib/Makefile                                 |   1 +
 lib/test_counters.c                          | 157 +++++++++++++++++
 tools/testing/selftests/lib/Makefile         |   1 +
 tools/testing/selftests/lib/config           |   1 +
 tools/testing/selftests/lib/test_counters.sh |   5 +
 21 files changed, 546 insertions(+), 74 deletions(-)
 create mode 100644 Documentation/core-api/counters.rst
 create mode 100644 include/linux/counters.h
 create mode 100644 lib/test_counters.c
 create mode 100755 tools/testing/selftests/lib/test_counters.sh

-- 
2.25.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32
  2020-10-06 20:44 [PATCH v2 00/11] Introduce Simple atomic counters Shuah Khan
@ 2020-10-06 20:44 ` Shuah Khan
  2020-10-07 18:16   ` Kees Cook
  2020-10-06 20:44 ` [PATCH v2 06/11] drivers/acpi/apei: " Shuah Khan
  2020-10-07 18:30 ` [PATCH v2 00/11] Introduce Simple atomic counters Kees Cook
  2 siblings, 1 reply; 6+ messages in thread
From: Shuah Khan @ 2020-10-06 20:44 UTC (permalink / raw)
  To: rafael, lenb, gregkh, keescook; +Cc: Shuah Khan, linux-acpi, linux-kernel

counter_atomic* is introduced to be used when a variable is used as
a simple counter and doesn't guard object lifetimes. This clearly
differentiates atomic_t usages that guard object lifetimes.

counter_atomic* variables will wrap around to 0 when it overflows and
should not be used to guard resource lifetimes, device usage and
open counts that control state changes, and pm states.

seqno is a sequence number counter for logging. This counter gets
incremented. Unsure if there is a chance of this overflowing. It
doesn't look like overflowing causes any problems since it is used
to tag the log messages and nothing more.

Convert it to use counter_atomic32.

This conversion doesn't change the overflow wrap around behavior.

Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/acpi/acpi_extlog.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
index f138e12b7b82..d1e733f15cf5 100644
--- a/drivers/acpi/acpi_extlog.c
+++ b/drivers/acpi/acpi_extlog.c
@@ -12,6 +12,7 @@
 #include <linux/ratelimit.h>
 #include <linux/edac.h>
 #include <linux/ras.h>
+#include <linux/counters.h>
 #include <asm/cpu.h>
 #include <asm/mce.h>
 
@@ -93,7 +94,7 @@ static struct acpi_hest_generic_status *extlog_elog_entry_check(int cpu, int ban
 static void __print_extlog_rcd(const char *pfx,
 			       struct acpi_hest_generic_status *estatus, int cpu)
 {
-	static atomic_t seqno;
+	static struct counter_atomic32 seqno;
 	unsigned int curr_seqno;
 	char pfx_seq[64];
 
@@ -103,7 +104,7 @@ static void __print_extlog_rcd(const char *pfx,
 		else
 			pfx = KERN_ERR;
 	}
-	curr_seqno = atomic_inc_return(&seqno);
+	curr_seqno = counter_atomic32_inc_return(&seqno);
 	snprintf(pfx_seq, sizeof(pfx_seq), "%s{%u}", pfx, curr_seqno);
 	printk("%s""Hardware error detected on CPU%d\n", pfx_seq, cpu);
 	cper_estatus_print(pfx_seq, estatus);
-- 
2.25.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH v2 06/11] drivers/acpi/apei: convert seqno counter_atomic32
  2020-10-06 20:44 [PATCH v2 00/11] Introduce Simple atomic counters Shuah Khan
  2020-10-06 20:44 ` [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32 Shuah Khan
@ 2020-10-06 20:44 ` Shuah Khan
  2020-10-07 18:17   ` Kees Cook
  2020-10-07 18:30 ` [PATCH v2 00/11] Introduce Simple atomic counters Kees Cook
  2 siblings, 1 reply; 6+ messages in thread
From: Shuah Khan @ 2020-10-06 20:44 UTC (permalink / raw)
  To: rafael, james.morse, tony.luck, bp, gregkh, keescook
  Cc: Shuah Khan, linux-acpi, linux-kernel, Borislav Petkov

counter_atomic* is introduced to be used when a variable is used as
a simple counter and doesn't guard object lifetimes. This clearly
differentiates atomic_t usages that guard object lifetimes.

counter_atomic* variables will wrap around to 0 when it overflows and
should not be used to guard resource lifetimes, device usage and
open counts that control state changes, and pm states.

seqno is a sequence number counter for logging. This counter gets
incremented. Unsure if there is a chance of this overflowing. It
doesn't look like overflowing causes any problems since it is used
to tag the log messages and nothing more.

Convert it to use counter_atomic32.

This conversion doesn't change the overflow wrap around behavior.

Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/acpi/apei/ghes.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 81bf71b10d44..92169436be18 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -41,6 +41,7 @@
 #include <linux/uuid.h>
 #include <linux/ras.h>
 #include <linux/task_work.h>
+#include <linux/counters.h>
 
 #include <acpi/actbl1.h>
 #include <acpi/ghes.h>
@@ -562,7 +563,7 @@ static void __ghes_print_estatus(const char *pfx,
 				 const struct acpi_hest_generic *generic,
 				 const struct acpi_hest_generic_status *estatus)
 {
-	static atomic_t seqno;
+	static struct counter_atomic32 seqno = COUNTER_ATOMIC_INIT(0);
 	unsigned int curr_seqno;
 	char pfx_seq[64];
 
@@ -573,7 +574,7 @@ static void __ghes_print_estatus(const char *pfx,
 		else
 			pfx = KERN_ERR;
 	}
-	curr_seqno = atomic_inc_return(&seqno);
+	curr_seqno = counter_atomic32_inc_return(&seqno);
 	snprintf(pfx_seq, sizeof(pfx_seq), "%s{%u}" HW_ERR, pfx, curr_seqno);
 	printk("%s""Hardware error from APEI Generic Hardware Error Source: %d\n",
 	       pfx_seq, generic->header.source_id);
-- 
2.25.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32
  2020-10-06 20:44 ` [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32 Shuah Khan
@ 2020-10-07 18:16   ` Kees Cook
  0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2020-10-07 18:16 UTC (permalink / raw)
  To: Shuah Khan; +Cc: rafael, lenb, gregkh, linux-acpi, linux-kernel

On Tue, Oct 06, 2020 at 02:44:36PM -0600, Shuah Khan wrote:
> counter_atomic* is introduced to be used when a variable is used as
> a simple counter and doesn't guard object lifetimes. This clearly
> differentiates atomic_t usages that guard object lifetimes.
> 
> counter_atomic* variables will wrap around to 0 when it overflows and
> should not be used to guard resource lifetimes, device usage and
> open counts that control state changes, and pm states.
> 
> seqno is a sequence number counter for logging. This counter gets
> incremented. Unsure if there is a chance of this overflowing. It
> doesn't look like overflowing causes any problems since it is used
> to tag the log messages and nothing more.
> 
> Convert it to use counter_atomic32.
> 
> This conversion doesn't change the overflow wrap around behavior.
> 
> Acked-by: Rafael J. Wysocki <rafael@kernel.org>
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Agreed: this looks like logging only.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v2 06/11] drivers/acpi/apei: convert seqno counter_atomic32
  2020-10-06 20:44 ` [PATCH v2 06/11] drivers/acpi/apei: " Shuah Khan
@ 2020-10-07 18:17   ` Kees Cook
  0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2020-10-07 18:17 UTC (permalink / raw)
  To: Shuah Khan
  Cc: rafael, james.morse, tony.luck, bp, gregkh, linux-acpi,
	linux-kernel, Borislav Petkov

On Tue, Oct 06, 2020 at 02:44:37PM -0600, Shuah Khan wrote:
> counter_atomic* is introduced to be used when a variable is used as
> a simple counter and doesn't guard object lifetimes. This clearly
> differentiates atomic_t usages that guard object lifetimes.
> 
> counter_atomic* variables will wrap around to 0 when it overflows and
> should not be used to guard resource lifetimes, device usage and
> open counts that control state changes, and pm states.
> 
> seqno is a sequence number counter for logging. This counter gets
> incremented. Unsure if there is a chance of this overflowing. It
> doesn't look like overflowing causes any problems since it is used
> to tag the log messages and nothing more.
> 
> Convert it to use counter_atomic32.
> 
> This conversion doesn't change the overflow wrap around behavior.
> 
> Acked-by: Rafael J. Wysocki <rafael@kernel.org>
> Acked-by: Borislav Petkov <bp@suse.de>
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Yup, also logging only, it seems.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v2 00/11] Introduce Simple atomic counters
  2020-10-06 20:44 [PATCH v2 00/11] Introduce Simple atomic counters Shuah Khan
  2020-10-06 20:44 ` [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32 Shuah Khan
  2020-10-06 20:44 ` [PATCH v2 06/11] drivers/acpi/apei: " Shuah Khan
@ 2020-10-07 18:30 ` Kees Cook
  2 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2020-10-07 18:30 UTC (permalink / raw)
  To: Shuah Khan
  Cc: corbet, gregkh, shuah, rafael, johannes, lenb, james.morse,
	tony.luck, bp, arve, tkjos, maco, joel, christian, hridya,
	surenb, minyard, arnd, mchehab, rric, linux-doc, linux-kernel,
	linux-kselftest, linux-acpi, devel, openipmi-developer,
	linux-edac

On Tue, Oct 06, 2020 at 02:44:31PM -0600, Shuah Khan wrote:
> -- Addressed Kees's  and Joel's comments:
>    1. Removed dec_return interfaces (Patch 1/11)
>    2. Removed counter_simple interfaces to be added later with changes
>       to drivers that use them (if any) (Patch 1/11)
>    3. Comment and Changelogs updates to Patch 2/11

Thanks!

> Kees, if this series is good, would you like to take this through your
> tree or would you like to take this through mine?

I think it's very close! I've sent reviews. Why don't you take this tree
for now? (Originally I thought this was going through Greg's tree since
it was touching a lot of drivers.)

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 6+ messages in thread

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Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-06 20:44 [PATCH v2 00/11] Introduce Simple atomic counters Shuah Khan
2020-10-06 20:44 ` [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32 Shuah Khan
2020-10-07 18:16   ` Kees Cook
2020-10-06 20:44 ` [PATCH v2 06/11] drivers/acpi/apei: " Shuah Khan
2020-10-07 18:17   ` Kees Cook
2020-10-07 18:30 ` [PATCH v2 00/11] Introduce Simple atomic counters Kees Cook

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