[Devel] [PATCH RH7] vfs: add warning in guard_bio_eod() if truncated_bytes > bvec->bv_len

[Roman Kagan]

On Sat, Dec 03, 2016 at 11:22:26AM +0300, Dmitry Monakhov wrote:
> 
> Pavel Tikhomirov <ptikhomirov at virtuozzo.com> writes:
> 
> > https://jira.sw.ru/browse/PSBM-55105
> >
> > In bug we crashed in zero_fill_bio when trying to zero memset bio_vec:
> >
> > struct bio_vec {
> >   bv_page = 0xffffea0004437500,
> >   bv_len = 4294948864,
> >   bv_offset = 0
> > }
> >
> > which is bigger than its bio->bi_size = 104448, guard_bio_eod might
> > lead to these bv_len overflow and is suspicious as quiet recently
> > in vz7.19.4 we've ported commit 2573b2539875("vfs: make guard_bh_eod()
> > more generic") which adds bv_len reduction, and before that there
> > were no crash.
> >
> > Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
> > ---
> >  fs/buffer.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/fs/buffer.c b/fs/buffer.c
> > index c45200d..b820080 100644
> > --- a/fs/buffer.c
> > +++ b/fs/buffer.c
> > @@ -3009,6 +3009,7 @@ void guard_bio_eod(int rw, struct bio *bio)
> >  
> >  	/* Truncate the bio.. */
> >  	bio->bi_size -= truncated_bytes;
> > +	WARN_ON(truncated_bytes > bvec->bv_len);
> BUG_ON would be more appropriate here.

Haven't you seen how Linus "critisized" Andrew for doing exactly that?

Roman.