Re: [PATCH] vfs: new O_NODE open flag

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, 28 Sep 2009, Andreas Dilger wrote:
> On Sep 28, 2009  12:25 +0200, Miklos Szeredi wrote:
> > BTW I just checked, and it is possible to re-open or promote an fd
> > opened with O_NODE like this:
> > 
> > 	char tmp[64];
> > 
> > 	fd = open(filename, O_NODE | O_NOACCESS);
> > 	/* ... */
> > 	sprintf(tmp, "/proc/self/fd/%i", fd);
> > 	fd_rw = open(tmp, O_RDWR);
> > 
> > Now fd_rw is guaranteed to refer to the same inode as fd.
> 
> It seems very unpleasant to require applications using O_NODE to
> reopen files using /proc.

The point of the above example was that reopening a file descriptor
with upgraded (or downgraded) access mode is even now possible.  Which
either means:

 a) the current permission model under /proc/PID/fd has a security
    hole (which Jamie is worried about)

 b) we can safely implement this with by changing openat() semantics,
    or even with a new reopen() syscall

I'm not too worried about the security aspect of this, but it's
something to keep in mind.

Thanks,
Miklos
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux