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Subject: Re: [PATCH] ext4: catch integer overflow in ext4_cache_extents
To:     Jan Kara <jack@suse.cz>, Ted Tso <tytso@mit.edu>
Cc:     linux-ext4@vger.kernel.org,
        Wolfgang Frisch <wolfgang.frisch@suse.com>
References: <20200713125818.21918-1-jack@suse.cz>
From:   Ritesh Harjani <riteshh@linux.ibm.com>
Date:   Mon, 13 Jul 2020 19:14:47 +0530
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On 7/13/20 6:28 PM, Jan Kara wrote:
> From: Wolfgang Frisch <wolfgang.frisch@suse.com>
> 
> When extent tree is corrupted we can hit BUG_ON in
> ext4_es_cache_extent(). Check for this and abort caching instead of
> crashing the machine.

Was it intentionally made corrupted by crafting a corrupted disk image?
Are there more such logic in place which checks for such corruption at 
other places? Maybe a background over the issue which you saw may help.
Also how did it recover out of it?

Do you think it make sense to still emit a WARN_ON() here and then
return which warns that this could possibly a corrupted extent
entry? (maybe WARN_ON_ONCE() or via some ratelimiting if multiple extent 
entries are corrupted for that inode).

-ritesh