linux-ext4 - Re: [PATCH 2/2] ext2fs: Fix off-by-one in dx_grow

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Message-ID: <20200410043321.GM45598@mit.edu>
Date:   Fri, 10 Apr 2020 00:33:21 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] ext2fs: Fix off-by-one in dx_grow_tree()

On Tue, Mar 31, 2020 at 04:30:35PM +0200, Jan Kara wrote:
> > > > Don't we have basically the same off-by-one in
> > > > e2fsck/pass1.c handle_htree() ?
> > > > 
> > > >        if ((root->indirect_levels > ext2_dir_htree_level(fs)) &&
> > > >            fix_problem(ctx, PR_1_HTREE_DEPTH, pctx))
> > > 
> > 
> > root->indirect_levels is zero based, while ext2_dir_htree_level()
> > returns the maximum number of levels (that is 3 by default). If I am
> > right then indirect_levels must always be smaller then
> > ext2_dir_htree_level() and that is how we use it everywhere else - the
> > palce I am pointing out is an exception and I think it's a bug.
> > 
> > Indeed it looks like the bug got introduced in
> > 3f0cf647539970474be8f607017ca7eccfc2fbbe
> > 
> > -       if ((root->indirect_levels > 1) &&
> > +       if ((root->indirect_levels > ext2_dir_htree_level(fs)) &&
> > 
> > Or am I missing something ?
> 
> Ah, you're indeed right! e2fsck/pass2.c even has a correct version of the
> condition. Just the condition in pass1.c is wrong.

I've applied the following fix on the maint branch.

     	     	 	       	      	    - Ted

commit 759b387775bfd5c9d3692680e5e4b929c3848d51
Author: Theodore Ts'o <tytso@....edu>
Date:   Fri Apr 10 00:30:52 2020 -0400

    e2fsck: fix off-by-one check when validating depth of an htree
    
    Fixes: 3f0cf6475399 ("e2fsprogs: add support for 3-level htree")
    
    Signed-off-by: Theodore Ts'o <tytso@....edu>

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index c9e8bf82..38afda48 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -2685,7 +2685,7 @@ static int handle_htree(e2fsck_t ctx, struct problem_context *pctx,
 		return 1;
 
 	pctx->num = root->indirect_levels;
-	if ((root->indirect_levels > ext2_dir_htree_level(fs)) &&
+	if ((root->indirect_levels >= ext2_dir_htree_level(fs)) &&
 	    fix_problem(ctx, PR_1_HTREE_DEPTH, pctx))
 		return 1;