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Tue, 20 Jan 2026 05:39:54 -0800 (PST) MIME-Version: 1.0 References: <20260112192827.25989-1-ethan.w.s.graham@gmail.com> <20260112192827.25989-3-ethan.w.s.graham@gmail.com> In-Reply-To: <20260112192827.25989-3-ethan.w.s.graham@gmail.com> From: Alexander Potapenko Date: Tue, 20 Jan 2026 14:39:17 +0100 X-Gm-Features: AZwV_Qhyxy4QYBC9vsg-1pl1r-iBwYh-56DZQ4fI_mrGZ4r5y44flCCfgaeUkgg Message-ID: Subject: Re: [PATCH v4 2/6] kfuzztest: implement core module and input processing To: Ethan Graham Cc: akpm@linux-foundation.org, andreyknvl@gmail.com, andy@kernel.org, andy.shevchenko@gmail.com, brauner@kernel.org, brendan.higgins@linux.dev, davem@davemloft.net, davidgow@google.com, dhowells@redhat.com, dvyukov@google.com, ebiggers@kernel.org, elver@google.com, gregkh@linuxfoundation.org, herbert@gondor.apana.org.au, ignat@cloudflare.com, jack@suse.cz, jannh@google.com, johannes@sipsolutions.net, kasan-dev@googlegroups.com, kees@kernel.org, kunit-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lukas@wunner.de, mcgrof@kernel.org, rmoar@google.com, shuah@kernel.org, sj@kernel.org, skhan@linuxfoundation.org, tarasmadan@google.com, wentaoz5@illinois.edu Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 9tbagxff38qgegr3fywtgbkfdhfqk7sa X-Rspam-User: X-Rspamd-Queue-Id: 8AFE320013 X-Rspamd-Server: rspam08 X-HE-Tag: 1768916395-193842 X-HE-Meta: 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 vHia3YHM GDXuNnqYNGg9aDJi+yVZL3YiT2sS3v4dlqR5lzhqzFIhmTmYbNrWRVSOxurdP658nds14WyGHbIS8xMZ1vIABpJ1XgUp0rjrZDfalbkayL/loueoZ9eZkHtSNuAoS64mA3aOPh40Qw+unDk7h++2Oj74gJg7jzBCwdostwV/K3ze0XmVymqPy6p/fpg6YAPrsss28JRqbSbCKDEHghKj2cyYr9Wd3oxvf4XMGISzr37AbYTN3waGt5SYceALRkF9UobmGFgPz/+NmiCIn5/XCjRRG634WqFhzIOzV5UQmpIXTAj8= 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, Jan 12, 2026 at 8:28=E2=80=AFPM Ethan Graham wrote: > + * Copyright 2025 Google LLC > + */ > +#include General comment: please include what you use. Make sure there are headers for e.g. add_taint(), pr_warn(), kzalloc(). > + * Taint the kernel on the first fuzzing invocation. The debugfs > + * interface provides a high-risk entry point for userspace to > + * call kernel functions with untrusted input. > + */ > + if (!test_taint(TAINT_TEST)) > + add_taint(TAINT_TEST, LOCKDEP_STILL_OK); > + > + if (len > KFUZZTEST_MAX_INPUT_SIZE) { > + pr_warn("kfuzztest: user input of size %zu is too large",= len); Let's change it to pr_warn_ratelimited() to avoid log spamming. Or maybe -EINVAL is enough for the userspace even without a log message? > + return -EINVAL; > + } > + > + buffer =3D kzalloc(len, GFP_KERNEL); > + if (!buffer) > + return -ENOMEM; > + > + ret =3D simple_write_to_buffer(buffer, len, off, buf, len); > + if (ret !=3D len) { > + kfree(buffer); > + return -EFAULT; I suggest returning `ret` here if it is < 0, and -EFAULT otherwise. > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include Missing for the allocation functions. > + /* Create the main "kfuzztest" directory in /sys/kernel/debug. */ > + state.kfuzztest_dir =3D debugfs_create_dir("kfuzztest", NULL); > + if (!state.kfuzztest_dir) { > + pr_warn("kfuzztest: could not create 'kfuzztest' debugfs = directory"); > + return -ENOMEM; Note: leaking state.target_fops here. > + for (targ =3D __kfuzztest_simple_targets_start; targ < __kfuzztes= t_simple_targets_end; targ++, i++) { > + state.target_fops[i].target_simple =3D (struct file_opera= tions){ > + .owner =3D THIS_MODULE, > + .write =3D targ->write_input_cb, > + }; > + err =3D initialize_target_dir(&state, targ, &state.target= _fops[i]); > + /* > + * Bail out if a single target fails to initialize. This = avoids > + * partial setup, and a failure here likely indicates an = issue > + * with debugfs. > + */ An initialization failure could result from something as simple as a name collision. Do we want to bail out in such cases?