Messages in this thread | | | From | Leon Yu <> | Date | Fri, 21 Oct 2016 20:47:27 +0800 | Subject | Re: [PATCH v2] proc: fix NULL dereference when reading /proc/<pid>/auxv |
| |
On Fri, Oct 21, 2016 at 3:21 AM, Michal Hocko <mhocko@kernel.org> wrote: > On Thu 20-10-16 19:04:39, Oleg Nesterov wrote: >> On 10/20, Leon Yu wrote: >> > >> > --- a/fs/proc/base.c >> > +++ b/fs/proc/base.c >> > @@ -1014,6 +1014,9 @@ static ssize_t auxv_read(struct file *file, char __user *buf, >> > { >> > struct mm_struct *mm = file->private_data; >> > unsigned int nwords = 0; >> > + >> > + if (!mm) >> > + return 0; >> > do { >> > nwords += 2; >> > } while (mm->saved_auxv[nwords - 2] != 0); /* AT_NULL */ >> >> Michal disagrees and I won't argue with his patch which makes __mem_open() >> fail if ->mm == NULL. Even if I don't really understand why should we change >> the old behaviour, this _can_ break or at least confuse something/someone. >> >> However, even if we do the change above, personally I do think we should >> fix the trivial bug first, then surprise the user-space. > > I am not objecting to this particular patch as it is obviously correct. > I was just hoping to have a more generic solution. The issue was > introduced in this merge window so it is not like we would need as > minimalistic approach possible. If the __mem_open approach sounds too > dangerous I will not pursue it. > > Anyway feel free to add > Acked-by: Michal Hocko <mhocko@suse.com> > for this patch.
Many thanks to all reviewers involved in this discussion for your valueable time and feedback.
-Leon
| |