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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=WUjVvSgY; 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 7DD2E606C900; Wed, 4 Nov 2026 19:23:19 +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=WUjVvSgY Received: by smtp.kernel.org (Postfix) with ESMTPSA id 055C01F000C1; Wed, 4 Nov 2026 19:23:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793820199; bh=9dtN9D2ek/PODLB9eXKISWT+1DyRVltUAnsYO5R4w7M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WUjVvSgYe5Hj7+VHJxqGCdVuPZtH9TtLIRIu84V4WAA6vFP1AvkW+oSj/edLc2ck/ AAJWe21jGN66rAVWXOLHwrW3BkgJ7C5MMC9kqPjYIm9KMsBUn46oa0vCJA/TU5q6rX iH5MZ7/d6lbSeiP9AbR9i30r2ap/96zzZx+nemJvi6mhYtlWM8sEF2UUpZwV40I+z3 +txyiwalAfhoSb0jj4BJxzYGfVLI7LPAybYz/+TrWrBDGQ0NUDbS+hRxwxJlmPbijJ EE86e3tlHpNNL7Pmd5DKa/IXf1VMJPtPlvfcVaYXoetHk9VmlRKFC3n8SLFdRpRElE JRmL7ZtyfUvGw== 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 RESEND v2 29/51] proc: don't walk through a non-directory when resolving a name Date: Wed, 4 Nov 2026 20:23:04 +0100 Message-ID: <20261104-work-procfs-bugfixes-v2-29-021c84d852e0@kernel.org> In-Reply-To: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> X-Mailing-List: linux-doc@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" 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=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9bnzfyJTJaHMu41dep952AaYXinG37t+WyDPu5f08x dN5TvXxjlIWBjEuBlkxRRaHdpNwueU8FZuNMjVg5rAygQxh4OIUgImwHGP4n7qS/1/T39mfA+ez nur5I3X/0v1ZE26+TomYpu8oNvN10zOG/0VzMx60c//Q3nGn5Li21/MFnmxuVnN23S5+YyFT+l7 1HzMA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit __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