linux-kernel - Re: [PATCH] bcachefs: fix oob in bch2_sb_clean_to

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Date: Wed,  8 May 2024 09:28:47 +0800
From: Edward Adam Davis <eadavis@...com>
To: kent.overstreet@...ux.dev
Cc: bfoster@...hat.com,
	eadavis@...com,
	linux-bcachefs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzbot+c48865e11e7e893ec4ab@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] bcachefs: fix oob in bch2_sb_clean_to_text

On Tue, 7 May 2024 21:21:16 -0400, Kent Overstreet wrote:
> > > > > diff --git a/fs/bcachefs/sb-clean.c b/fs/bcachefs/sb-clean.c
> > > > > index 35ca3f138de6..194e55b11137 100644
> > > > > --- a/fs/bcachefs/sb-clean.c
> > > > > +++ b/fs/bcachefs/sb-clean.c
> > > > > @@ -278,6 +278,17 @@ static int bch2_sb_clean_validate(struct bch_sb *sb,
> > > > >  		return -BCH_ERR_invalid_sb_clean;
> > > > >  	}
> > > > > 
> > > > > +	for (struct jset_entry *entry = clean->start;
> > > > > +	     entry != vstruct_end(&clean->field);
> > > > > +	     entry = vstruct_next(entry)) {
> > > > > +		if ((void *) vstruct_next(entry) > vstruct_end(&clean->field)) {
> > > > > +			prt_str(err, "entry type ");
> > > > > +			bch2_prt_jset_entry_type(err, le16_to_cpu(entry->type));
> > > > > +			prt_str(err, " overruns end of section");
> > > > > +			return -BCH_ERR_invalid_sb_clean;
> > > > > +		}
> > > > > +	}
> > > > > +
> > > > The original judgment here is sufficient, there is no need to add this section of inspection.
> > > 
> > > No, we need to be able to print things that failed to validate so that
> > > we see what went wrong.
> > The follow check work fine, why add above check ?
> >    1         if (vstruct_bytes(&clean->field) < sizeof(*clean)) {
> >   268                 prt_printf(err, "wrong size (got %zu should be %zu)",
> >     1                        vstruct_bytes(&clean->field), sizeof(*clean));
> > 
> 
> You sure you're not inebriated?
Here, is my test log, according to it, I can confirm what went wrong.
[  129.350671][ T7772] bcachefs (/dev/loop0): error validating superblock: Invalid superblock section clean: wrong size (got 8 should be 24)
[  129.350671][ T7772] clean (size 8):
[  129.350671][ T7772] flags:          0
[  129.350671][ T7772] journal_seq:    0