From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6276D48B383 for ; Wed, 1 Jul 2026 13:34:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782912898; cv=none; b=I51ZmOR5Zvkh+O/omkINDpxYvI9+gXwf4saNbUJqHwMVgpmXOztHRtTAGr0VnDNszn4zxLeAmIVlextk+Vwro5MyYpajC6t+0uTsejaCokqeFGBIUxa6Dgub+q4i7VqlNLzgTquvKgDyk4Q2eEHl5TaC+j829myekcZMRpR2nkc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782912898; c=relaxed/simple; bh=3mQqrk1JLHVHrm5RRmEjYJ+UL5NnMeiT9NzeOGsiJU8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=kg3mE53KgF5xesT/fifJZ5B29zXDlJH2RlfY6uGOfO8QNLK0mYEgWGzf/QtRkP3NRSo9oaKjUgJW851U/1FTElD8H8dsntH3InefZxpTWSMx4Mfjx08SkFqahLF9cK8AxYWKx2wzYbLqlcdz62gOP+/KmcJE7FM1ZY/jMxwVjVw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qrFsgtxV; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="qrFsgtxV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CA911F00A3A; Wed, 1 Jul 2026 13:34:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1782912895; bh=xZqsf/RJoaulb8zvH8A9PAfXrWQEAnBhTJaZ8KNc7d0=; h=From:To:Cc:Subject:Date:Reply-To; b=qrFsgtxV4XQRHzFSXbKv8doz3jRvVG7y9iFOPbz0h6N72v8k6rpIYw3I9FiTityTF qdKabnp4LD1cn4vuTEM2UCpYuREXl6IO5j0CkAtQ5J1Qi9IJNo6gXJh1mKxlZjgR+u dK7ykxnCTnsH03xTrlYLcRuKcjUINnxiNPmiRYmU= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-53341: fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh() Date: Wed, 1 Jul 2026 15:34:56 +0200 Message-ID: <2026070144-CVE-2026-53341-64ff@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3898; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=1la2DR6x4Rh37FHDbTsQAxEt4gVEugHNbsE/wfAPmvo=; b=owGbwMvMwCRo6H6F97bub03G02pJDFmu4iVBT/YLtl70sAgN6Q7e3TFz5ppXqfMu96Zluz+ce cSxIa+9I5aFQZCJQVZMkeXLNp6j+ysOKXoZ2p6GmcPKBDKEgYtTACbiqsKwYEr5a6Eofc8F/zX4 lNXtbv1+U6j+kGFBN+PHezqMnVwtk9R+RfuZ2N4My8gEAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh() may_decode_fh() accesses mount::mnt_ns without holding any locks; that means the mount can concurrently be unmounted, and the mnt_namespace can concurrently be freed after an RCU grace period. This race can happens as follows, assuming that the mount point was created by open_tree(..., OPEN_TREE_CLONE): thread 1 thread 2 RCU __do_sys_open_by_handle_at do_handle_open handle_to_path may_decode_fh is_mounted [mount::mnt_ns access] [mount::mnt_ns access] __do_sys_close fput_close_sync __fput dissolve_on_fput umount_tree class_namespace_excl_destructor namespace_unlock free_mnt_ns mnt_ns_tree_remove call_rcu(mnt_ns_release_rcu) mnt_ns_release_rcu mnt_ns_release kfree [mnt_namespace::user_ns access] **UAF** Fix it by taking rcu_read_lock() around the mount::mnt_ns access, like in __prepend_path(). Additionally, document the semantics of mount::mnt_ns, and use WRITE_ONCE() for writers that can race with lockless readers. This bug is unreachable unless one of the following is set: - CONFIG_PREEMPTION - CONFIG_RCU_STRICT_GRACE_PERIOD because it requires an RCU grace period to happen during a syscall without an explicit preemption. This doesn't seem to have interesting security impact; worst-case, it could leak the result of an integer comparison to userspace (from the level check in cap_capable()), cause an endless loop, or crash the kernel by dereferencing an invalid address. The Linux kernel CVE team has assigned CVE-2026-53341 to this issue. Affected and fixed versions =========================== Issue introduced in 6.11 with commit 620c266f394932e5decc4b34683a75dfc59dc2f4 and fixed in 6.18.36 with commit 32138633e51e6db59e474765cf93268c92b42888 Issue introduced in 6.11 with commit 620c266f394932e5decc4b34683a75dfc59dc2f4 and fixed in 7.0.13 with commit a8ed2c29fcfdac78db96c9da4e659c8a513f2a94 Issue introduced in 6.11 with commit 620c266f394932e5decc4b34683a75dfc59dc2f4 and fixed in 7.1 with commit 40ab6644b99685755f740b872c00ef40d9aa870e Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-53341 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/fhandle.c fs/mount.h fs/namespace.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/32138633e51e6db59e474765cf93268c92b42888 https://git.kernel.org/stable/c/a8ed2c29fcfdac78db96c9da4e659c8a513f2a94 https://git.kernel.org/stable/c/40ab6644b99685755f740b872c00ef40d9aa870e