On Tue, Aug 28, 2018 at 12:36:22PM +0000, Ahmed S. Darwish wrote:
> On Tue, Aug 28, 2018 at 02:15:01AM +0300, Alexey Dobriyan wrote:
> > ---
> > fs/proc/base.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
>
> Missing description and S-o-b. Further comments below..
>
> > diff --git a/fs/proc/base.c b/fs/proc/base.c
> > index 33f444721965..668e465c86b3 100644
> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> > @@ -3549,11 +3549,11 @@ static int proc_task_readdir(struct file *file,
> > struct dir_context *ctx)
> > for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
> > task;
> > task = next_tid(task), ctx->pos++) {
> > - char name[10 + 1];
> > - unsigned int len;
> > + char name[10], *p = name + sizeof(name);
> > +
>
> Multiple issues:
>
> - len should be 11, as was in the original code
> (0xffffffff = 4294967295, 10 letters)
len should be 10.
> - while we're at it, let's use a constant for the '11' instead of
> mysterious magic numbers
>
> - 'p' is clearly overflowing the stack here
>
> > tid = task_pid_nr_ns(task, ns);
> > - len = snprintf(name, sizeof(name), "%u", tid);
> > - if (!proc_fill_cache(file, ctx, name, len,
> > + p = _print_integer_u32(p, tid);
> > + if (!proc_fill_cache(file, ctx, p, name + sizeof(name) - p,
>
> You're replacing snprintf() code __that did proper len checking__
> with code that does not. That's not good.
Yes, the whole point of the patch is to skip length checking.
> I can't see how the fourth proc_fill_cache() parameter, ``name +
> sizeof(name)'' safely ever replace the original 'len' parameter.
> It's a pointer value .. (!)
>
> Overall this looks like a broken patch submitted by mistake.
