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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=gMV7oMe2; 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 5CBF26080A5C; Mon, 2 Nov 2026 15:20:09 +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=gMV7oMe2 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 976621F00A1D; Mon, 2 Nov 2026 15:19:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793632809; bh=gDybWaXH0yVqSHGh6cSao1kY+huQ+XTPXQ1Vld4D+UM=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=gMV7oMe2qdf0+aS9olfnOBAqn/OBe6DasxdwT9LImBIs7Pj7CDa/oA2a6B/8kY9pd QfSD+01vRhmQIdCiXlwTDyOpKHr/+vYVKI1GFm8wQR5ZwmzCN80Jrz/IWpqVDIWfYl 3Bzlzk4aLDYzHqqx14bF+dEvwX8XoOta/BsfktGPBtManOh4//zemOTXkilWggqbhn W/RtVoTwiEMKAtL6JeSwBY8eTWp9GpOtjwbXtxAZExlQVzQlk62v23yj30uR9SnWUe jbKIL4QwYWDm+Xox3mBmfSoPFHGyBgWuJOAs5l7OErmCDLr8xRUVWg57VzoW07Bk1H D+JLNSysS0GGw== From: Christian Brauner Date: Mon, 02 Nov 2026 16:07:12 +0100 Subject: [PATCH RFC 02/27] jfs: let procfs copy in writes to the loglevel file X-Mailing-List: linux-fbdev@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" Content-Transfer-Encoding: 7bit Message-Id: <20261102-work-procfs-fs-v1-2-d09a996317b3@kernel.org> References: <20261102-work-procfs-fs-v1-0-d09a996317b3@kernel.org> In-Reply-To: <20261102-work-procfs-fs-v1-0-d09a996317b3@kernel.org> 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 X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=1370; i=brauner@kernel.org; h=from:subject:message-id; bh=izEZyN2ciF2azWBwOiarD7rxdH5SrLb74RUgxhmuQ3M=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9WG7IJf+71NVUmNfmjuySXN5GYdHLr8WmWM125JvlY 84Qs/VxRykLgxgXg6yYIotDu0m43HKeis1GmRowc1iZQIYwcHEKwES0PBgZHvWw/qhbNX2Pi9i5 F4F+xcfDMxt+ZB+X21+0fPH/f32bHBkZLj5bwyh982HI2kgp1W2/Husu5Fmlc+PU8aMTrX5F3I/ u5gEA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Implement ->proc_write_buf() so procfs copies in what is written before it pins the entry, and take the level from that copy. Writes larger than PAGE_SIZE - 1 bytes fail with -EINVAL now and so do empty writes, which looked at a byte that wasn't written before. Signed-off-by: Christian Brauner (Amutable) --- fs/jfs/jfs_debug.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/fs/jfs/jfs_debug.c b/fs/jfs/jfs_debug.c index 5eb35b0d420f..e1c0211a6a32 100644 --- a/fs/jfs/jfs_debug.c +++ b/fs/jfs/jfs_debug.c @@ -23,13 +23,10 @@ static int jfs_loglevel_proc_show(struct seq_file *m, void *v) return 0; } -static ssize_t jfs_loglevel_proc_write(struct file *file, - const char __user *buffer, size_t count, loff_t *ppos) +static ssize_t jfs_loglevel_proc_write(struct file *file, char *buffer, + size_t count, loff_t *ppos) { - char c; - - if (get_user(c, buffer)) - return -EFAULT; + char c = buffer[0]; /* yes, I know this is an ASCIIism. --hch */ if (c < '0' || c > '9') @@ -40,7 +37,7 @@ static ssize_t jfs_loglevel_proc_write(struct file *file, static const struct proc_ops jfs_loglevel_proc_ops = { .proc_show = jfs_loglevel_proc_show, - .proc_write = jfs_loglevel_proc_write, + .proc_write_buf = jfs_loglevel_proc_write, }; #endif -- 2.53.0