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b=l/9K700WtETbZbiehxECDLdPCEeiiVRA3kxFDmgS/2nKE79+mMwEbcSj3UAdFTEXx 6DvGrmpdgDVXnGX30oyGp8h1wecxAk4jKzxRW9aGPBdJy0OisIoFIZFTfdpRhDfBXZ KAYYL329Lr/1W5cMHSII0yRN2tcUg68lTIkupTY2K2vtTItr3nAhe86PuUrEx8QrzH ZRKhA68sEbKxiE5OFQB7qDtLFMKmYizYX4WKQpNV8RKMwbhLf5julp7cLNgPDZarPP /qEweKu2GyB/uW3f9G490N5UiUnYW1jY6yf/ITOz6Ini0L9UMQPzrnkmfsWQJTfyzK rW/DJSvgmGkgg== From: Christian Brauner Date: Mon, 02 Nov 2026 15:21:19 +0100 Subject: [PATCH RFC 04/38] s390/dasd: don't look in front of the buffer on an empty write X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261102-work-procfs-bugfixes-v1-4-59422ed3e465@kernel.org> References: <20261102-work-procfs-bugfixes-v1-0-59422ed3e465@kernel.org> In-Reply-To: <20261102-work-procfs-bugfixes-v1-0-59422ed3e465@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 , stable@vger.kernel.org X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=952; i=brauner@kernel.org; h=from:subject:message-id; bh=vNxDJDpmoyfXJahneUuQ9vEH9eL70g/8w71rNTJgUxc=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9mJM1jeXQ3NW7/xZeaxDpdlGIUkjat+D7tG9pahOcr AOsJk6611HKwiDGxSArpsji0G4SLrecp2KzUaYGzBxWJpAhDFycAnCRCYwMn44HG9tefO3daCl/ zObZjudV2/8stZoz4eUdbl4NjbdfLRkZLu1okv36OdkxUVB7scSNP4VzvOQn7V+ZlPZqvbKOm44 /IwA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9F99940003 X-Stat-Signature: qdcu1e9tzio51tfbks85fiukxkz6rm3i 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-Rspam-User: X-HE-Tag: 1793629365-140953 X-HE-Meta: U2FsdGVkX1/5PDeHHC7i7jqeWlCRqYd2+zm7/yhHM2H6DdffyqbMMOjwiC4argHUNILhnrPbFqAgjNrzk/23hCVttWM2wmEY9Lq8pQsebf/0AAuN6ymsYDOFRIPKpsomS+y3tkeBuMTmZAZO+HWHGoP/VoQcbqvMTv6ZGqLMaob/RYGQEsnOHpqpE5Ctj31D/qye6M2wXGfu8hhrmDouk3MjYrah0Spk+lm1+TvEONd5+1SLv00VNHROZtMf7wyXzxWVAle+3+W8Ce1ibRm63hFd1r+IGiTtnyxZxqCPfINeFUga19j0TT9ftn1xrXPoVJJuZbPOE7y8HmJzkUltPWZPeco72Tgm6vHbHntxXxxyajSwken87ckMc8uVhvy3e4cAchpj6PI489vwnfHek5tsgctiGx3Xfc/Jr0uEtfx4uGyDCyn3DD9x2DXtOqNi/MO4+IEO97tpeUnDY8c2KGluH+XKW3yavdK6SQE/DN92eIUlKruyuHzPApbyoVZ3j4FjriUVqejaC+OsIAvuBWaTEzqyTS5vpX/jUlM4+HxMUDijn8JpwZjZPDb2bgK1LvtChs6y/t0zRiGRN1bL882pdpQx8L1SR9TL9OUoWDOa/BwWH5a8uqdiEYlIEhQVUKb0Q0jVy2zi0M/fni1uqNK0W3P7P6SK6rbR+IrQAlDUKcGIJIHYlUkSmtaQZkNVZ07PlMD4RXzQtNGHNtkbYhv63mCwVU8c1bRx1b/Dwa6DhAoKvKXj1ii1j2UZcJwsD7bdUwB3DKp8LSCT74qPIWlWnLKQl5R7hisA1+RBFTW0CSckWNiExVAJg0AyPSEuE7cAJrx7kTZJEkpfsVx+m0V1Eou90tLa68VyrJ20smdiucgM/K6Vvk5drUiod2t/s3SROMCbQ3QAn5sJuolNy+rcg94sdAIWIB29tkrz4678FoD7RBwsLO1wdElZ/EyMPMoAiDQutkpzMOKS0WJ XFR9apOG ZsXT4HvNNLYClPIjnlC7MdrzM/hDMAwCt6XpcwGY2XrmMTXcbhCFbetkj4NbbVOLQiSUHYGjNkW6Ho0xOPeQdGgNd8ODJyftmPGdNgdWZw14EOXLrbJnLB0ygSsBuf9UknZFD2a4umesUDm/Wt9W9Y3FoSgsJlmQpTk+6sBSTBW+c6coNcrvnJ5BmrnMe3P9kTn62x5UtsHrP5+vQuIoCH5JuZpGS3t3sYKeRsTUmMNSGmp+/ubQY2TH8WdrS+Ijoi4G5QjLUQjQpeQxjU1Eozr3V9+gxhI3l9gNQN5T31mDZSU9xUSruKjbP7w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 dasd_get_user_string() strips a trailing newline by looking at the last byte that was written. For an empty write that's the byte in front of the buffer it just allocated. Only look if something was written. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- drivers/s390/block/dasd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c index 2ffe404b890f..e97891e58957 100644 --- a/drivers/s390/block/dasd.c +++ b/drivers/s390/block/dasd.c @@ -933,7 +933,7 @@ char *dasd_get_user_string(const char __user *user_buf, size_t user_len) return ERR_PTR(-EFAULT); } /* got the string, now strip linefeed. */ - if (buffer[user_len - 1] == '\n') + if (user_len && buffer[user_len - 1] == '\n') buffer[user_len - 1] = 0; else buffer[user_len] = 0; -- 2.53.0