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Thu, 04 Sep 2025 01:54:10 -0700 (PDT) MIME-Version: 1.0 References: <20250901164212.460229-1-ethan.w.s.graham@gmail.com> <20250901164212.460229-6-ethan.w.s.graham@gmail.com> In-Reply-To: <20250901164212.460229-6-ethan.w.s.graham@gmail.com> From: Alexander Potapenko Date: Thu, 4 Sep 2025 10:53:32 +0200 X-Gm-Features: Ac12FXzGXGcfd1LWU7AL2P0uHHVI9Cjfbatglasugt3XjpaIrqiLrO1UVJEntQs Message-ID: Subject: Re: [PATCH v2 RFC 5/7] kfuzztest: add ReST documentation To: Ethan Graham Cc: ethangraham@google.com, andreyknvl@gmail.com, brendan.higgins@linux.dev, davidgow@google.com, dvyukov@google.com, jannh@google.com, elver@google.com, rmoar@google.com, shuah@kernel.org, tarasmadan@google.com, kasan-dev@googlegroups.com, kunit-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, dhowells@redhat.com, lukas@wunner.de, ignat@cloudflare.com, herbert@gondor.apana.org.au, davem@davemloft.net, linux-crypto@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 8syj6xez9i1zxooq1am7zbptawb6fnzc X-Rspam-User: X-Rspamd-Queue-Id: C2CFB140006 X-Rspamd-Server: rspam01 X-HE-Tag: 1756976051-547140 X-HE-Meta: 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 XAAikoVC rERp8DrLN1IqgCCcnftRrOfdiM7K4vnjriZ7P6gmO4RO/ed7yfqI6v9eKMiTGy8jbXDBh/HYZ1N3nqkcHZD9pxm/5RGLOb1Q/GFtRRYQzdbAKwGaweDekcaBmptSwTyTjNWq0Q4iR53zaw/ybwlKimyRvmTo9Yk2/X9ua3Z7BgK4rQ5RCQd8f+1Py7oCSkWr/l8vUFLugqrWNyCdjia35oDqnnQhgHK/HWmeqNQKGTrk0jiNZH0BiDUu8LK3iaJkbMcz3p43Jl/wryJWFPHyWCE+2ww== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 1, 2025 at 6:43=E2=80=AFPM Ethan Graham wrote: > > From: Ethan Graham > > Add Documentation/dev-tools/kfuzztest.rst and reference it in the > dev-tools index. > > Signed-off-by: Ethan Graham Acked-by: Alexander Potapenko Some nits below. > +Macros ``FUZZ_TEST``, `KFUZZTEST_EXPECT_*`` and ``KFUZZTEST_ANNOTATE_*``= embed Nit: missing second backtick before KFUZZTEST_EXPECT_ > +Input Format > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +KFuzzTest targets receive their inputs from userspace via a write to a d= edicated > +debugfs ``/sys/kernel/debug/kfuzztest//input``. Nit: "debugfs file"? > +- Padding and Poisoning: The space between the end of one region's data = and the > + beginning of the next must be sufficient for padding. In KASAN builds, > + KFuzzTest poisons this unused padding, allowing for precise detection = of > + out-of-bounds memory accesses between adjacent buffers. This padding s= hould > + be at least ``KFUZZTEST_POISON_SIZE`` bytes as defined in > + `include/linux/kfuzztest.h``. Nit: missing leading backtick. > + > +KFuzzTest Bridge Tool > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +The kfuzztest-bridge program is a userspace utility that encodes a rando= m byte Nit: do we need backticks around kfuzztest-bridge? > +This tool is intended to be simple, both in usage and implementation. It= s > +structure and DSL are sufficient for simpler use-cases. For more advance= d > +coverage-guided fuzzing it is recommended to use syzkaller which impleme= nts > +deeper support for KFuzzTest targets. Nit: please add a link to syzkaller. > + > +The textual format is a human-readable representation of the region-base= d binary > +format used by KFuzzTest. It is described by the following grammar: > + > +.. code-block:: text > + > + schema ::=3D region ( ";" region )* [";"] > + region ::=3D identifier "{" type+ "}" Don't types need to be separated with spaces? > + type ::=3D primitive | pointer | array | length | string > + primitive ::=3D "u8" | "u16" | "u32" | "u64" > + pointer ::=3D "ptr" "[" identifier "]" > + array ::=3D "arr" "[" primitive "," integer "]" > + length ::=3D "len" "[" identifier "," primitive "]" > + string ::=3D "str" "[" integer "]" > + identifier ::=3D [a-zA-Z_][a-zA-Z1-9_]* > + integer ::=3D [0-9]+ > + > +Pointers must reference a named region. To fuzz a raw buffer, the buffer= must be Maybe insert a paragraph break between these two sentences? > +.. code-block:: text > + > + my_struct { ptr[buf] len[buf, u64] }; buf { arr[u8, n] }; > + > +Where ``n`` is some integer value defining the size of the byte array in= side of s/Where/, where/ ?