linux-ext4 - Re: [PATCH] e2fsck: avoid overflow with very large dirs

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Date:   Wed, 4 Mar 2020 18:39:11 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Andreas Dilger <adilger@...mcloud.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e2fsck: avoid overflow with very large dirs

On Tue, Feb 11, 2020 at 06:07:21PM -0700, Andreas Dilger wrote:
> In alloc_size_dir() it multiples signed ints when allocating the
> buffer for rehashing an htree-indexed directory.  This will overflow
> when the directory size is above 4GB, which is possible with largedir
> directories having about 100M entries, assuming an average 3/4 leaf
> fullness and 24-byte filenames, or fewer with longer filenames.
> The same problem exisgs in get_next_block().
> 
> Similarly, the out_dir struct used a signed int for the number of
> blocks in the directory, which may result in a negative size if the
> directory is over 2GB (about 50M entries or fewer).
> 
> Use appropriate unsigned variables for block counts, and use larger
> types for calculating the byte count for memory offsets/sizes.
> 
> Such large directories not been seen yet, but are not too far away.
> The ext2fs_get_array() function will properly calculate the needed
> memory allocation, and detect overflow on 32-bit systems.
> Add ext2fs_resize_array() to do the same for array resize.
> 
> Signed-off-by: Andreas Dilger <adilger@...mcloud.com>
> Lustre-bug-id: https://jira.whamcloud.com/browse/LU-13197

Applied, thanks.  I had to make a slight change to fix a "merge
conflict" with the patch.

					- Ted