linux-kernel - [PATCH -1/24] exec: Don't open code get_close_on

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87k0tqr6zi.fsf_-_@x220.int.ebiederm.org>
Date:   Wed, 09 Dec 2020 15:42:57 -0600
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jann@...jh.net>
Subject: [PATCH -1/24] exec: Don't open code get_close_on_exec


Al Viro pointed out that using the phrase "close_on_exec(fd,
rcu_dereference_raw(current->files->fdt))" instead of wrapping it in
rcu_read_lock(), rcu_read_unlock() is a very questionable
optimization[1].

Once wrapped with rcu_read_lock()/rcu_read_unlock() that phrase
becomes equivalent the helper function get_close_on_exec so
simplify the code and make it more robust by simply using
get_close_on_exec.

[1] https://lkml.kernel.org/r/20201207222214.GA4115853@ZenIV.linux.org.uk
Suggested-by: Al Viro <viro@....linux.org.uk>
Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---

I aim to rebase my exec branch and apply this tomorrow.

 fs/exec.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 547a2390baf5..9aabf6e8c904 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1808,8 +1808,7 @@ static int bprm_execve(struct linux_binprm *bprm,
 	 * inaccessible after exec. Relies on having exclusive access to
 	 * current->files (due to unshare_files above).
 	 */
-	if (bprm->fdpath &&
-	    close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
+	if (bprm->fdpath && get_close_on_exec(fd))
 		bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
 
 	/* Set the unchanging part of bprm->cred */
-- 
2.20.1