Date: Sat,  1 Jun 2024 18:56:15 +0200
From: Erick Archer <erick.archer@...look.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	Matthew Wilcox <mawilcox@...rosoft.com>
Cc: Erick Archer <erick.archer@...look.com>,
	x86@...nel.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH v4 0/3] Hardening perf subsystem

Hi everyone,

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].

In the first patch, the "struct amd_uncore_ctx" can be refactored to
use a flex array for the "events" member. This way, the allocation/
freeing of the memory can be simplified. Then, the struct_size()
helper can be used to do the arithmetic calculation for the memory
to be allocated.

In the second patch, as the "struct intel_uncore_box" ends in a
flexible array, the preferred way in the kernel is to use the
struct_size() helper to do the arithmetic instead of the calculation
"size + count * size" in the kzalloc_node() function.

In the third patch, as the "struct perf_buffer" also ends in a
flexible array, the preferred way in the kernel is to use the
struct_size() helper to do the arithmetic instead of the calculation
"size + count * size" in the kzalloc_node() functions. At the same
time, prepare for the coming implementation by GCC and Clang of the
__counted_by attribute.

This time, I have decided to send these three patches in the same serie
since all of them has been rejected by the maintainers. I have used
the v4 tag since it is the latest iteration in one of the patches.

The reason these patches were rejected is that Peter Zijlstra detest
the struct_size() helper [3][4]. However, Kees Cook and I consider that
the use of this helper improves readability. But we can all say that it
is a matter of preference.

Anyway, leaving aside personal preferences, these patches has the
following pros:

- Code robustness improvement (__counted_by coverage).
- Code robustness improvement (use of struct_size() to do calculations
  on memory allocator functions).
- Fewer lines of code.
- Follow the recommendations made in "Deprecated Interfaces, Language
  Features, Attributes, and Conventions" [5] as the preferred method
  of doing things in the kernel.
- Widely used in the kernel.
- Widely accepted in the kernel.

There are also patches in this subsystem that use the struct_size()
helper:

6566f907bf31 ("Convert intel uncore to struct_size") by Matthew Wilcox
dfbc411e0a5e ("perf/x86/rapl: Prefer struct_size() over open coded arithmetic") by me

Therefore, I would like these patches to be applied this time.

Best regards,
Erick

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Link: https://lore.kernel.org/linux-hardening/20240430091833.GD40213@noisy.programming.kicks-ass.net [3]
Link: https://lore.kernel.org/linux-hardening/20240430091504.GC40213@noisy.programming.kicks-ass.net [4]
Link: https://docs.kernel.org/process/deprecated.html [5]
---
Changes in v4:

- Add the "Reviewed-by:" tag to the three patches.
- Rebase against linux next (tag next-20240531).

Previous versions:

perf/x86/amd/uncore: Add flex array to struct amd_uncore_ctx
  v1 -> https://lore.kernel.org/linux-hardening/AS8PR02MB7237E4848B44A5226BD3551C8BE02@AS8PR02MB7237.eurprd02.prod.outlook.com/

perf/x86/intel/uncore: Prefer struct_size over open coded arithmetic
  v1 -> https://lore.kernel.org/linux-hardening/AS8PR02MB7237F4D39BF6AA0FF40E91638B392@AS8PR02MB7237.eurprd02.prod.outlook.com/

perf/ring_buffer: Prefer struct_size over open coded arithmetic
  v3 -> https://lore.kernel.org/linux-hardening/AS8PR02MB72379B4807F3951A1B926BA58BE02@AS8PR02MB7237.eurprd02.prod.outlook.com/
  v2 -> https://lore.kernel.org/linux-hardening/AS8PR02MB7237569E4FBE0B26F62FDFDB8B1D2@AS8PR02MB7237.eurprd02.prod.outlook.com/
  v1 -> https://lore.kernel.org/linux-hardening/AS8PR02MB72372AB065EA8340D960CCC48B1B2@AS8PR02MB7237.eurprd02.prod.outlook.com/

  Changes in v3:
  - Refactor the logic, compared to the previous version, of the second
    rb_alloc() function to gain __counted_by() coverage (Kees Cook and
    Christophe JAILLET).

  Changes in v2:
  - Annotate "struct perf_buffer" with __counted_by() attribute (Kees Cook).
  - Refactor the logic to gain __counted_by() coverage (Kees Cook).
---
Erick Archer (3):
  perf/x86/amd/uncore: Add flex array to struct amd_uncore_ctx
  perf/x86/intel/uncore: Prefer struct_size over open coded arithmetic
  perf/ring_buffer: Prefer struct_size over open coded arithmetic

 arch/x86/events/amd/uncore.c   | 18 +++++-------------
 arch/x86/events/intel/uncore.c |  7 +++----
 kernel/events/internal.h       |  2 +-
 kernel/events/ring_buffer.c    | 15 ++++-----------
 4 files changed, 13 insertions(+), 29 deletions(-)

-- 
2.25.1

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