From: Al Viro <viro@ZenIV.linux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Willy Tarreau <w@1wt.eu>,
Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.cz>, yalin wang <yalin.wang2010@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5] fs: clear file privilege bits when mmap writing
Date: Thu, 10 Dec 2015 20:27:49 +0000 [thread overview]
Message-ID: <20151210202749.GF20997@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAGXu5jLF5-jbQ8tEHWnTZKqWj5_kmrqdKcJMb_B_HdN34RwCqA@mail.gmail.com>
On Thu, Dec 10, 2015 at 11:47:18AM -0800, Kees Cook wrote:
> In open, sure, but what about under mm/memory.c where we're trying to
> twiddle it from vma->file->f_flags as in my patch? That seemed like it
> would want atomic safety.
Sigh... Again, I'm not at all convinced that this is the right approach,
but generally you need ->f_lock. And in situations where the bit can
go only off->on, check it lockless, skip the whole thing entirely if it's
already set and grab the spinlock otherwise.
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WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Willy Tarreau <w@1wt.eu>,
Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.cz>, yalin wang <yalin.wang2010@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5] fs: clear file privilege bits when mmap writing
Date: Thu, 10 Dec 2015 20:27:49 +0000 [thread overview]
Message-ID: <20151210202749.GF20997@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAGXu5jLF5-jbQ8tEHWnTZKqWj5_kmrqdKcJMb_B_HdN34RwCqA@mail.gmail.com>
On Thu, Dec 10, 2015 at 11:47:18AM -0800, Kees Cook wrote:
> In open, sure, but what about under mm/memory.c where we're trying to
> twiddle it from vma->file->f_flags as in my patch? That seemed like it
> would want atomic safety.
Sigh... Again, I'm not at all convinced that this is the right approach,
but generally you need ->f_lock. And in situations where the bit can
go only off->on, check it lockless, skip the whole thing entirely if it's
already set and grab the spinlock otherwise.
next prev parent reply other threads:[~2015-12-10 20:27 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-09 22:51 [PATCH v5] fs: clear file privilege bits when mmap writing Kees Cook
2015-12-09 22:51 ` Kees Cook
2015-12-10 1:21 ` Christoph Hellwig
2015-12-10 1:21 ` Christoph Hellwig
2015-12-10 3:25 ` Kees Cook
2015-12-10 3:25 ` Kees Cook
2015-12-10 4:14 ` Al Viro
2015-12-10 4:14 ` Al Viro
2015-12-10 7:06 ` Willy Tarreau
2015-12-10 7:06 ` Willy Tarreau
2015-12-10 7:10 ` Willy Tarreau
2015-12-10 7:10 ` Willy Tarreau
2015-12-10 18:05 ` Kees Cook
2015-12-10 18:05 ` Kees Cook
2015-12-10 18:16 ` Willy Tarreau
2015-12-10 18:16 ` Willy Tarreau
2015-12-10 18:18 ` Kees Cook
2015-12-10 18:18 ` Kees Cook
2015-12-10 19:33 ` Al Viro
2015-12-10 19:33 ` Al Viro
2015-12-10 19:47 ` Kees Cook
2015-12-10 19:47 ` Kees Cook
2015-12-10 20:27 ` Al Viro [this message]
2015-12-10 20:27 ` Al Viro
2015-12-10 21:45 ` Kees Cook
2015-12-10 21:45 ` Kees Cook
2015-12-10 21:56 ` Al Viro
2015-12-10 21:56 ` Al Viro
2015-12-10 22:00 ` Kees Cook
2015-12-10 22:00 ` Kees Cook
-- strict thread matches above, loose matches on Subject: below --
2015-12-10 22:33 Kees Cook
2016-01-07 19:36 ` Kees Cook
2016-01-08 0:30 ` Andy Lutomirski
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