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Date: Fri, 1 Dec 2023 08:24:10 -0800
From: "Darrick J. Wong" <djwong@kernel.org>
To: Brian Norris <briannorris@chromium.org>
Cc: Theodore Ts'o <tytso@mit.edu>, linux-ext4@vger.kernel.org
Subject: Re: [PATCH] lib/ext2fs: Validity checks for
 ext2fs_inode_scan_goto_blockgroup()
Message-ID: <20231201162410.GA36164@frogsfrogsfrogs>
References: <20231201000126.335263-1-briannorris@chromium.org>
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On Thu, Nov 30, 2023 at 04:01:18PM -0800, Brian Norris wrote:
> We don't validate the 'group' argument, so it's easy to get underflows
> or crashes here.
> 
> This resolves issues seen in ureadahead, when it uses an old packfile
> (with mismatching group indices) with a new filesystem.

Say what now?  The boot time pre-caching thing Ubuntu used to have?
https://manpages.ubuntu.com/manpages/trusty/man8/ureadahead.8.html

--D

> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
> 
>  lib/ext2fs/inode.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/lib/ext2fs/inode.c b/lib/ext2fs/inode.c
> index 957d5aa9f9d6..96d854b5fb69 100644
> --- a/lib/ext2fs/inode.c
> +++ b/lib/ext2fs/inode.c
> @@ -313,6 +313,9 @@ static errcode_t get_next_blockgroup(ext2_inode_scan scan)
>  errcode_t ext2fs_inode_scan_goto_blockgroup(ext2_inode_scan scan,
>  					    int	group)
>  {
> +	if (group <= 0 || group >= scan->fs->group_desc_count)
> +		return EXT2_ET_INVALID_ARGUMENT;
> +
>  	scan->current_group = group - 1;
>  	scan->groups_left = scan->fs->group_desc_count - group;
>  	scan->bad_block_ptr = 0;
> -- 
> 2.43.0.rc2.451.g8631bc7472-goog
> 
>