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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DVG35mDd; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EE995606A31B; Wed, 4 Nov 2026 17:48:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DVG35mDd Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E9FB1F00919; Wed, 4 Nov 2026 17:47:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793814487; bh=+QMuJvtMuQ+CXnn6xLeWoxU7H9VJY0mzKEyTXi76/+M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DVG35mDdrJ+w70lYp9CqgpxTuoGTpj4temyLsY3vuBl9elVVBnmHrviotaVGY/ppP UdOgypZXpDWtJ7enRd3iIIX4vWx3xyqPaHPzOZWq/P4JUJrwgIpI4MwtSTSz/6po8R Yvz02Y/vDREj2xNfVXWxFSvrw7Bvuiwjqz0knxKP5rsjzaWDW5qaKyJ9F3yEnh+EWh A3TtW5nyoi8NpYae3YAaKFmJ3QPX5Rij2cVvQ/1JMiWehFHBZSo4em6YfVuXhfiqDi JqHLo3hhdvujnwykhoFrIyHzHBnGpPwJgUwVLui5mJv4lfTVDRPXKF7pOVu2XHYste DuNdex110TFZw== From: Christian Brauner To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Jann Horn , Josef Bacik , Chris Mason , Jeff Layton , NeilBrown , Eric Dumazet , Thomas Gleixner , Al Viro , Jonathan Corbet , Christoph Hellwig , Greg Kroah-Hartman , Joel Granados , Kees Cook , Jan Kara , Jan Kara , linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-um@lists.infradead.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, ntfs3@lists.linux.dev, platform-driver-x86@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, netfilter-devel@vger.kernel.org, dri-devel@lists.freedesktop.org, ibm-acpi-devel@lists.sourceforge.net, jfs-discussion@lists.sourceforge.net, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-cifs@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-mm@kvack.org, linux-sh@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, sparclinux@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-doc@vger.kernel.org, linux-serial@vger.kernel.org, linux-atm-general@lists.sourceforge.net, Takashi Iwai , linux-input@vger.kernel.org, linux-raid@vger.kernel.org, linux-ext4@vger.kernel.org, linux-modules@vger.kernel.org, linux-debuggers@vger.kernel.org, "Christian Brauner (Amutable)" , Chuck Lever , stable@vger.kernel.org Subject: [PATCH v2 13/51] sched/psi: don't drop the last byte of a trigger write Date: Wed, 4 Nov 2026 18:46:59 +0100 Message-ID: <20261104-work-procfs-bugfixes-v2-13-bbf7d5546809@kernel.org> In-Reply-To: <20261104-work-procfs-bugfixes-v2-0-bbf7d5546809@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-bbf7d5546809@kernel.org> X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=1310; i=brauner@kernel.org; h=from:subject:message-id; bh=/5ST8groFWC3ZYrB9+5K2L5OtN8hrslkTr6MpvXzbng=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9zjv/59LFdb+4Nqzr+cU3P2cS7+L2yauySvlfWb8/9 eufsCjT0o5SFgYxLgZZMUUWh3aTcLnlPBWbjTI1YOawMoEMYeDiFICJmJkw/FM9sG/u0ochUvwi r25NnfqcY/Wv3m+1Rk6yc5TfvmHn3j+V4X8gx3Wx2Wp7OP7b/lW+zLTMQ+Qde1X2zk2aTqESmTX LCxkA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit psi_write() copies at most 32 bytes of the write into its buffer and terminates the buffer by overwriting its last byte. For a write shorter than 32 bytes that is the last byte the writer sent. A trigger written without a trailing newline loses its last digit then, "some 150000 1000000" turns into "some 150000 100000", and a shorter one like "some 150 10000" fails with -EINVAL because the window doesn't fit anymore. Only writes that end in a newline parse as intended. Copy at most 31 bytes and terminate behind them. Fixes: 0e94682b73bf ("psi: introduce psi monitor") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- kernel/sched/psi.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 7c5381423334..8b59635e95d4 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1566,11 +1566,11 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf, if (!nbytes) return -EINVAL; - buf_size = min(nbytes, sizeof(buf)); + buf_size = min(nbytes, sizeof(buf) - 1); if (copy_from_user(buf, user_buf, buf_size)) return -EFAULT; - buf[buf_size - 1] = '\0'; + buf[buf_size] = '\0'; seq = file->private_data; -- 2.53.0