Re: [Qemu-devel] [PATCH 0/6] Multi-level page tables and userland mapping fixes, v3

[Riku Voipio <riku.voipio@iki.fi>]

On Mon, Mar 15, 2010 at 04:08:46PM +0100, Jan-Simon Möller wrote:
> Am Montag, 15. März 2010 15:48:03 schrieb Riku Voipio:
> > On Mon, Mar 15, 2010 at 01:46:10PM +0100, Jan-Simon Möller wrote:
> > > root@frodo:/# qemu-arm -strace /sbin/ldconfig.real
> > > 16359 uname(0x403fef78) = 0
> > > 16359 brk(NULL) = 0x000a9000
> > > 16359 brk(0x000a9d08) = 0x000a9d08
> > > 16359 open("/dev/urandom",O_RDONLY) = 3
> > > 16359 read(3,0x403ff27d,3) = 3
> > > 16359 close(3) = 0
> > > [...]
> > > 16359 stat64("/usr/lib/libgettextlib.so",0x403fdf28) = 0
> > > 16359 stat64("/usr/lib/libgettextpo.so.0",0x403fdec0) = 0
> > > 16359 stat64("/usr/lib/libgettextpo.so.0.4.0",0x403fdf28) = 0
> > > 16359 stat64("/usr/lib/libpython2.6.so.1.0",0x403fdec0) = 0
> > > 16359 stat64("/usr/lib/libpython2.6.so.1.0",0x403fdf28) = 0
> > > 16359 open("/etc/ld.so.cache~",O_WRONLY|O_CREAT|O_NOFOLLOW|O_TRUNC,0600)
> > > = 3 16359 write(3,0xb03d0,1288) = 1288
> > > 16359 write(3,0x403ff0a0,0) = -1 errno=14 (Bad address)
 
> > A zero sized write. According to manpage ok.
 
> > In qemu we do a lock_user to to get the string to write. Richards change
> >  changes the access checks the get called by lock_user:

> > page_check_range:
> > 
> > -    if (start + len < start)
> > -        /* we've wrapped around */
> > ...
> > +    if (start + len - 1 < start) {
> > +        /* We've wrapped around.  */
> > 
> > This now blows up with len = 0;

> Confirmed. A quick test with  if (len > 0) around and ldconfig.real runs.

Richard, would you be ok with that change? Or should we rather have explicit 

if (len == 0) return 0;

?