From: Al Viro <viro@zeniv.linux.org.uk>
To: Aleksa Sarai <cyphar@cyphar.com>
Cc: Song Liu <songliubraving@fb.com>,
linux-ia64@vger.kernel.org, linux-doc@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Alexei Starovoitov <ast@kernel.org>,
linux-kernel@vger.kernel.org, David Howells <dhowells@redhat.com>,
linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org,
containers@lists.linux-foundation.org,
Christian Brauner <christian.brauner@ubuntu.com>,
linux-api@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
linux-arch@vger.kernel.org, linux-s390@vger.kernel.org,
Tycho Andersen <tycho@tycho.ws>,
Daniel Borkmann <daniel@iogearbox.net>,
Jonathan Corbet <corbet@lwn.net>, Jiri Olsa <jolsa@redhat.com>,
linux-sh@vger.kernel.org,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
linux-arm-kernel@lists.infradead.org, Yonghong Song <yhs@fb.com>,
linux-mips@vger.kernel.o
Subject: Re: [PATCH v17 10/13] namei: LOOKUP_{IN_ROOT,BENEATH}: permit limited ".." resolution
Date: Mon, 25 Nov 2019 00:35:01 +0000 [thread overview]
Message-ID: <20191125003501.GF4203@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20191117011713.13032-11-cyphar@cyphar.com>
On Sun, Nov 17, 2019 at 12:17:10PM +1100, Aleksa Sarai wrote:
> + if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
> + /*
> + * If there was a racing rename or mount along our
> + * path, then we can't be sure that ".." hasn't jumped
> + * above nd->root (and so userspace should retry or use
> + * some fallback).
> + */
> + if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
> + return -EAGAIN;
> + if (unlikely(read_seqretry(&rename_lock, nd->r_seq)))
> + return -EAGAIN;
> + }
Looks like excessive barriers to me - it's
rmb
check mount_lock.sequence
rmb
check rename_lock.sequence
> @@ -2266,6 +2274,10 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
> nd->last_type = LAST_ROOT; /* if there are only slashes... */
> nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
> nd->depth = 0;
> +
> + nd->m_seq = read_seqbegin(&mount_lock);
> + nd->r_seq = read_seqbegin(&rename_lock);
Same here, pretty much (fetch/rmb/fetch/rmb)
next prev parent reply other threads:[~2019-11-25 0:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-17 1:17 [PATCH v17 00/13] open: introduce openat2(2) syscall Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 01/13] namei: only return -ECHILD from follow_dotdot_rcu() Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 02/13] nsfs: clean-up ns_get_path() signature to return int Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 03/13] namei: allow nd_jump_link() to produce errors Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 04/13] namei: allow set_root() " Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 05/13] namei: LOOKUP_NO_SYMLINKS: block symlink resolution Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 06/13] namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 07/13] namei: LOOKUP_NO_XDEV: block mountpoint crossing Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 08/13] namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution Aleksa Sarai
2019-11-25 0:26 ` Al Viro
2019-11-25 6:03 ` Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 09/13] namei: LOOKUP_IN_ROOT: chroot-like " Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 10/13] namei: LOOKUP_{IN_ROOT,BENEATH}: permit limited ".." resolution Aleksa Sarai
2019-11-25 0:35 ` Al Viro [this message]
2019-11-25 13:21 ` Aleksa Sarai
2019-11-28 10:10 ` Aleksa Sarai
2019-11-17 1:17 ` [PATCH v17 11/13] open: introduce openat2(2) syscall Aleksa Sarai
2019-11-25 0:37 ` Al Viro
2019-11-17 1:17 ` [PATCH v17 12/13] selftests: add openat2(2) selftests Aleksa Sarai
2019-11-17 1:28 ` [PATCH v17 13/13] Documentation: path-lookup: include new LOOKUP flags Aleksa Sarai
2019-11-25 0:39 ` [PATCH v17 00/13] open: introduce openat2(2) syscall Al Viro
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