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b=LcsHmz5fK/rq4Bthqez6bEjgj3XEj/c4XKC7cTJTsyy7D8CM7px4kYtiPIzpCal3e YBnBaglaHwrkG0flLB3F5W7+c/cuVEsjWKHrViqroXNJjS/gLfGejJZpTfdZwQ3hxC MmTHns7R80U7RN5yvO/p+jAHpSlpp28zonoPL5JONcxOoGjLH7eL2t5N/YO/Ar8kN9 Uv53YRcqkSaZvuCyD2wDiglbNsEmatVgs/O4H1aOlq+Q2Fx7/kPdW3ED163deYMdjW mzDyj/1PR2eJIDW/uTXVOsrPDnM7bk3qNxgMT69wH0jr1TOdByT+AbZB6eZHAK8Tua TqbNm9ftkTIoQ== 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 29/51] proc: don't walk through a non-directory when resolving a name Date: Wed, 4 Nov 2026 18:47:15 +0100 Message-ID: <20261104-work-procfs-bugfixes-v2-29-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-Archived-By: 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=2403; i=brauner@kernel.org; h=from:subject:message-id; bh=syoXv99Xi8HZbn/gUZHMWCnjRlLtpR5bAeJLx/CLQI8=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9znvEfdPiys++q6WXg17bqvjo1yRcanm93G/LTAvP+ yo6V5wqOkpZGMS4GGTFFFkc2k3C5ZbzVGw2ytSAmcPKBDKEgYtTACZSps7I8Lk1e9tBje0T0qw2 XN3x9V66cYxZdMKvVWWifA53/z6tv8nwT2XZnUOOz2p0hO4vzbeojJFe8k4sMSUqVEPr/fE7CSI PWQE= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-Stat-Signature: bc6ueog89hu1aqh4zth4nnb9p455861z X-Rspamd-Server: rspam01 X-Rspam-User: 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-Rspamd-Queue-Id: E341E40004 X-HE-Tag: 1793814793-553654 X-HE-Meta: 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 mulf9yfv sZAmeocO47qh5TAyltNaxEcV1rKOCCgnZ380a2vMhQBawXIet/s1EcDqw+siiXqazm1WPx7vZDvm6DsnSZnIAmtHmJnKWBM5VxH7j1HeYYdLSuTDIU5XwKe/EJ2I1/zhdKIejttB6BTlZTONQQRMgeN1d5vVhJ2AGzOQPqIEuHoatpuVKoBaqumi9byNng0RAao5Rec1MPV5EjuuGdVzHGbTDfY6Wu0hGVOYOWx7cM43LPXQEaZDbM9NPmXP4vUxksYHhD1lz+9vvHV7NB7CY9uYmp3j2bI/lbeQ8QKTgfOV3l9gjBlyHGLy09Uoaz+2YyQtWGZUTYcuxa5rRxrJCwFdZdRyVu0aOdM+Ld5Uwvrvk4QsS+CEDbKgAAAMO14r2zyh95ns+saAXyaBuR5lseuJe3OZANyIzPwbR8JbKDAfH130dBiqUxiV00w== 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 __xlate_proc_name() walks the components of a name like "a/b/c" and takes whatever it finds for "a" and "b" as the directory to go on in. It never checks that they actually are directories. So proc_create("file/x") hangs x into the subdir tree of the regular file "file". Nobody can look x up there, but remove_proc_subtree() on the file removes and frees x along with it, behind the back of whoever registered x. pktgen passes the name the writer of "add_device" picks to proc_create_data(), and only the part in front of the '@' has to name a network device: echo "add_device lo@" > /proc/net/pktgen/kpktgend_0 echo "add_device lo@/x" > /proc/net/pktgen/kpktgend_1 echo "rem_device_all" > /proc/net/pktgen/kpktgend_0 echo "rem_device_all" > /proc/net/pktgen/kpktgend_1 The third write frees both entries and the fourth one makes kpktgend_1 call proc_remove() on the freed second one: BUG: KASAN: slab-use-after-free in proc_remove+0x8f/0xa0 Read of size 8 at addr ff110001134c8e70 by task kpktgend_1/243 Call Trace: proc_remove+0x8f/0xa0 pktgen_remove_device.isra.0+0x118/0x500 pktgen_rem_all_ifs+0xeb/0x1a0 pktgen_thread_worker+0x1b42/0x7280 The files of a network namespace belong to the root of its user namespace and these writes don't require a capability. So once pktgen is loaded an unprivileged user can do this in namespaces of its own. Treat a component that isn't a directory like one that doesn't exist. All names with a '/' that the tree passes in as literals only walk through directories. pktgen is fixed separately to not pass such names in the first place. Reported-by: Chris Mason Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- fs/proc/generic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 4c3fcaf68ef4..6ac9c4c13897 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -170,7 +170,7 @@ static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret, de = *ret ?: &proc_root; while ((next = strchr(cp, '/')) != NULL) { de = pde_subdir_find(de, cp, next - cp); - if (!de) { + if (!de || !S_ISDIR(de->mode)) { WARN(1, "name '%s'\n", name); return -ENOENT; } -- 2.53.0