linux-kernel - Re: O_TMPFILE fs corruption (Re: Linux 3.11-rc4)

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Date:	Sun, 4 Aug 2013 20:45:16 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@....edu>, Al Viro <viro@...iv.linux.org.uk>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: O_TMPFILE fs corruption (Re: Linux 3.11-rc4)

The patch looks right to me - we should pass in similar flags for the
create case as for tmpfile to the filesystem.

But let's make sure we're all on the same page. Al?

                 Linus

On Sun, Aug 4, 2013 at 7:34 PM, Andy Lutomirski <luto@....edu> wrote:
> On 08/04/2013 02:09 PM, Linus Torvalds wrote:
>>
>> It's that time of the week again..
>
>
> I still get filesystem corruption with O_TMPFILE.  The program below, run as
> flinktest foo proc (or flinktest foo linkat if you're root) will produce a
> bogus inode.  On ext4, once the inode is gone from cache, the inode will be
> impossible to delete and will require a fsck to fix
>
> A patch (not necessarily the appropriate fix) is here:
>
> http://article.gmane.org/gmane.linux.kernel/1537088
>
> --- cut here ---
>
> #include <stdio.h>
> #include <err.h>
> #include <fcntl.h>
> #include <unistd.h>
> #include <string.h>
>
> #define __O_TMPFILE 020000000
> #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
> #define AT_EMPTY_PATH 0x1000
>
> int main(int argc, char **argv)
> {
>   char buf[128];
>
>   if (argc != 3)
>     errx(1, "Usage: flinktest PATH linkat|proc");
>
>   int fd = open(".", O_TMPFILE | O_RDWR, 0600);
>   if (fd == -1)
>     err(1, "O_TMPFILE");
>   write(fd, "test", 4);
>
>   if (!strcmp(argv[2], "linkat")) {
>     if (linkat(fd, "", AT_FDCWD, argv[1], AT_EMPTY_PATH) != 0)
>       err(1, "linkat");
>   } else if (!strcmp(argv[2], "proc")) {
>     sprintf(buf, "/proc/self/fd/%d", fd);
>     if (linkat(AT_FDCWD, buf, AT_FDCWD, argv[1], AT_SYMLINK_FOLLOW) != 0)
>       err(1, "linkat");
>   } else {
>     errx(1, "invalid mode");
>   }
>   return 0;
> }
>
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