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Mon, 2 Nov 2026 15:26:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793633234; bh=XTKgYPXjwGtd+Y2GluPCJ0QXSAilsjtjyt0vuaHdwds=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=kxAPIiB8bZX2oCCzHcBO+Z+9M3+BVX1rvIx7nyXXRvMDmlNh8VaOR2aKmZd2R34hH Gw7+HXTv7VzusgWsZ9GsA33MUpaeH7qM1+3/U0mI5dpdOtBvO7SVe8UgtTS9zRl74w zVpSeL4wIOUBkjK4em3j/1wqw6UAi3uG8FIvW3rat4+P86CWAWdzAlWUQvV7vMVEpa S38kzwkwiuMhgYyorFO1fD6ITanbo/Z9kHp1r8cLKvafivXAqupn5zK/psHYFqdIdf /8feMEEXHbH1Vr1KKZJEdv5qVbaXwV5kRtN7tZQOORDjsgRAwj5Ih1oUQUGUkibHAd /P9IyT6izArUA== From: Christian Brauner Date: Mon, 02 Nov 2026 16:07:31 +0100 Subject: [PATCH RFC 21/27] dyndbg: let procfs copy in writes to /proc/dynamic_debug/control X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , Precedence: list X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261102-work-procfs-fs-v1-21-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=2226; i=brauner@kernel.org; h=from:subject:message-id; bh=DMKbMmltc6KGAMcxoyJUHD9hv4JrUkNBMnfQsx/+9Q8=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9WG7ceqHmw/8zQZt7jtfybdlxWv7H8x3cq8MvN69Km /uTde1Zq45SFgYxLgZZMUUWh3aTcLnlPBWbjTI1YOawMoEMYeDiFICJONky/M//M+f6NIdFl39X +W2ZGKtX/Hnx0w8TwmWPzuNxWv/xS38Hw1/hO5kJ4eWe3065F7wIPZknI/zsrm6z8qW9zQ0q7Vs 0K5gA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Move the parsing into ddebug_proc_write_buf() and implement ->proc_write_buf() with it so procfs copies in what is written before it pins the entry. The debugfs file keeps copying in itself. Writes larger than USER_BUF_PAGE - 1 bytes to the procfs file now fail with -EINVAL from procfs instead of -E2BIG. Signed-off-by: Christian Brauner (Amutable) --- lib/dynamic_debug.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index 64a211290872..1d6012c9eb41 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -1002,11 +1002,28 @@ __setup("dyndbg=", dyndbg_setup); * command text from userspace, parses and executes it. */ #define USER_BUF_PAGE 4096 + +static ssize_t ddebug_proc_write_buf(struct file *file, char *buf, size_t len, + loff_t *offp) +{ + int ret; + + if (len == 0) + return 0; + v2pr_info("read %zu bytes from userspace\n", len); + + ret = ddebug_exec_queries(buf, NULL); + if (ret < 0) + return ret; + + *offp += len; + return len; +} + static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf, size_t len, loff_t *offp) { - char *tmpbuf; - int ret; + char *tmpbuf __free(kfree) = NULL; if (len == 0) return 0; @@ -1017,15 +1034,7 @@ static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf, tmpbuf = memdup_user_nul(ubuf, len); if (IS_ERR(tmpbuf)) return PTR_ERR(tmpbuf); - v2pr_info("read %zu bytes from userspace\n", len); - - ret = ddebug_exec_queries(tmpbuf, NULL); - kfree(tmpbuf); - if (ret < 0) - return ret; - - *offp += len; - return len; + return ddebug_proc_write_buf(file, tmpbuf, len, offp); } /* @@ -1196,7 +1205,8 @@ static const struct file_operations ddebug_proc_fops = { static const struct proc_ops proc_fops = { .proc_seq_ops = &ddebug_proc_seqops, .proc_state_size = sizeof(struct ddebug_iter), - .proc_write = ddebug_proc_write + .proc_write_buf = ddebug_proc_write_buf, + .proc_write_size = USER_BUF_PAGE - 1, }; static void ddebug_attach_module_classes(struct ddebug_table *dt, -- 2.53.0