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SubjectRe: [bug] crash when reading /proc/mounts (was: Re: Linux 2.6.23-rc9 and a heads-up for the 2.6.24 series..)
* Al Viro <viro@ftp.linux.org.uk> wrote:

> On Wed, Oct 03, 2007 at 10:46:07AM +0200, Ingo Molnar wrote:
> >
> > hm, i just triggered the procfs crash below with -rc9 on a testbox.
> > Config attached. It's easy to reproduce it via 'service sshd restart'.
> > The crash site is:
> >
> > (gdb) list *0xc017599d
> > 0xc017599d is in seq_path (fs/seq_file.c:354).
> > 349 if (m->count < m->size) {
> > 350 char *s = m->buf + m->count;
> > 351 char *p = d_path(dentry, mnt, s, m->size - m->count);
> > 352 if (!IS_ERR(p)) {
> > 353 while (s <= p) {
> > 354 char c = *p++;
> > 355 if (!c) {
> > 356 p = m->buf + m->count;
> > 357 m->count = s - m->buf;
> > 358 return s - p;
> > (gdb)
> >
> > any ideas? Fortunately i was able to do an strace of the incident:
>
> Charming... So we get d_path() either returning junk or we get
> something that isn't NUL-terminated. Which one it is? I.e. what does
> p look like and what's in s?

could be use-after-free as well, as CONFIG_PAGEALLOC was enabled.

Ingo
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