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b=RuiXMui8BjXqcKpOkZSSb2fzdRJqOkdTcBMExOILHIUKi584gE62EX9Rp9REsxAIh tjfzstrESrt5D/m0KQUF1dxAhGVFfymG0E8Js/U44Ve00018P7C9iKFESKyfNdRPH7 jxqcAf+UyNqrfhgRtXxl4xxVCit/7IAdifFgBcmNi28pEmExfPZqlZQ4Q0GbNWzpIU msgRoEl0hgaDf8LmrTDw9dYe6Yf6s53ZTxmKCSoEgxdjVUtQjEYNmUbpSyhFg70PwG 1lAYyQW6WwhB8zxcVpIbbkLDhHR6Rqo3KCYBrHb/1mUtI2SL/iwP/I6AQGkAgYxSJ7 LV6XKXIW55awQ== From: Christian Brauner Date: Mon, 02 Nov 2026 15:21:31 +0100 Subject: [PATCH RFC 16/38] proc: don't walk through a non-directory when resolving a name X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261102-work-procfs-bugfixes-v1-16-59422ed3e465@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=2403; i=brauner@kernel.org; h=from:subject:message-id; bh=/ELhSiescDaKRjbpWYPGx1ceLHTHmhSA6KoiiBWZ7Vg=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9mJOt9OXTNdZ5WT/1Ui5nzeZtP2wlv61nddee+08Ux Eyii1I+d5SyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAEykaAvD/7pF4SLFW7W7Qx48 CBf6zy7QHPZPaforsYxZ6W92nFswPYbhf+p3tsbuWgVbTQW7NyaGa9/nmy3g0Lj3LuPQBLv7vNr OzAA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 X-Rspamd-Queue-Id: 5C5A31C000F X-Stat-Signature: uqjg4xgm4o9tzrp5nhwjfqdtd6ms8dc9 X-Rspamd-Server: rspam04 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: 1793629533-422987 X-HE-Meta: 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 iHIj8XkK Ns1jbFSI+TOknwzhoBm31OTo2RDB3rxD1So0NgmVZ4RE7Zcc1L8bzbTLSHBnPVCMILduhPBNEDGbHKWXZhLpt246k3igaqViOz495PQQGebmDvnnaJ9jQ4XtRqj2Nj6Ll9qTfewrOmags8FyhFx4KCIQU0o1Jr6qiJVjq317lmCmDjMVGSm0wP7r8+qcMlNcl7AH8+MHnseGvwGAQ0ZhH+ieKchdji9ZDFNa/oROhKS7/2DDLeLMuxg1tFrryNH+D8Brnf990m415SNNL30KKwknpJpkLkYQ8ir47xKvU2D0Q99Sp855I3JDe/99lMLlyxXki 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 2b1971da4a85..c560c96a64eb 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