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 4DFA634E75A; Wed, 30 Sep 2026 19:13:29 +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=1790795610; cv=none; b=QmbCCbnFAWvgRhQZ/E5hGnThcZaWHQHpRVzGwQeKjThCTuLf2CKC6FekLKXOaxkpX6toiYt1QqhbjavjzLkuhKxqjkviDaowtPax/Z2JLUScoFRYuztTPMHBHji7KSLdFpVhd/Tx+sx38RRdiw1R4paOOW2h3dmX4eBrKfiuLRA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790795610; c=relaxed/simple; bh=2fc2EdBI8vQ/MsB+bbh/yRl5j/anDkrdhelZoHmtCrM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mgQQkaMQvxUhFDqW8+udbFIlf47wY+O1QaZk/cg18ju19wRbgdePiu8qDDhg734HPzBaYU2lCruTHQWa1/oPgsM9AS1a8tFBK98IgPnC+STBcnQo4Z21pQWk+DiU95i85a/x5+xoBsmo78l+rb/d4pcsKxkgkNY1Q4HogLwoDqs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gQyAufrD; 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="gQyAufrD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6B291F000FF; Wed, 30 Sep 2026 19:13:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790795609; bh=0CZ9MA7wxegabbKJUPSyj+gpWm2J65S/hGHeipMwVr4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gQyAufrDN1y0VM+2aAhgRM4FnqMmPqx/5LiBao0jSQAcsMc/eBOuMmIVeC8OdLzI0 qK6Tm/eTP9dcuQ5T+DGR7MxJaVRM2lvGCsie8p7E5GoWPIeyu/RDYFprg2whA4V8JH C+TsiIFaRsg9kzkHD18PRrnyoTDPuElwZutqr+7I= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Benjamin Peterson , Jann Horn , Jan Kara , "Christian Brauner (Amutable)" Subject: [PATCH 6.6 0622/1193] exec: do_close_on_exec() before taking exec_update_lock Date: Wed, 30 Sep 2026 17:21:46 +0200 Message-ID: <20260930152448.063095215@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit e780259b54e618ceb4763fbc21314acf3565e813 upstream. do_close_on_exec() currently happens while holding the exec_update_lock, which is used in a lot of places that access process state to synchronize access checks. I recently added another such use of exec_update_lock, causing a regression. do_close_on_exec() can block waiting for a reply from a filesystem. That means a hung filesystem can block codepaths that use exec_update_lock; and it also means that a FUSE filesystem which attempts to inspect the calling process can deadlock. To avoid such problems, move do_close_on_exec() before the exec_update_lock is taken, but after the FD table has been copied if necessary. I have looked through all the calls between the old and new position of the do_close_on_exec() call; there seems to be no file descriptor table access in between. Reported-by: Benjamin Peterson Closes: https://lore.kernel.org/r/f5e8166a-88be-46c5-8939-1e5227ffe4c2@app.fastmail.com Fixes: 6650527444da ("proc: protect ptrace_may_access() with exec_update_lock (part 1)") Cc: stable@vger.kernel.org Signed-off-by: Jann Horn Link: https://patch.msgid.link/20260907-cloexec-before-exec-update-lock-v1-1-8018c201a7df@google.com Tested-by: Benjamin Peterson Reviewed-by: Jan Kara Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -1274,6 +1274,20 @@ int begin_new_exec(struct linux_binprm * goto out; /* + * We have to apply CLOEXEC before we change whether the process is + * dumpable (in setup_new_exec) to avoid a race with a process in userspace + * trying to access the should-be-closed file descriptors of a process + * undergoing exec(2). + * + * This can block on filesystem ->flush() handlers, including waiting + * for FUSE daemons, so do it before exec_mmap takes the + * exec_update_lock. + * This must happen after the point of no return, and after unsharing + * the FD table. + */ + do_close_on_exec(me->files); + + /* * Must be called _before_ exec_mmap() as bprm->mm is * not visible until then. Doing it here also ensures * we don't race against replace_mm_exe_file(). @@ -1323,14 +1337,6 @@ int begin_new_exec(struct linux_binprm * clear_syscall_work_syscall_user_dispatch(me); - /* - * We have to apply CLOEXEC before we change whether the process is - * dumpable (in setup_new_exec) to avoid a race with a process in userspace - * trying to access the should-be-closed file descriptors of a process - * undergoing exec(2). - */ - do_close_on_exec(me->files); - if (bprm->secureexec) { /* Make sure parent cannot signal privileged process. */ me->pdeath_signal = 0;