linux-ext4 - Re: [1/6] f2fs: check entire encrypted bigname when finding a dentry

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Date:   Sun, 30 Apr 2017 02:19:22 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     linux-fscrypt@...r.kernel.org, Jaegeuk Kim <jaegeuk@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net, linux-ext4@...r.kernel.org,
        linux-mtd@...ts.infradead.org,
        Gwendal Grignou <gwendal@...omium.org>, hashimoto@...omium.org,
        kinaba@...omium.org, stable@...r.kernel.org,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [1/6] f2fs: check entire encrypted bigname when finding a dentry

On Mon, Apr 24, 2017 at 10:00:08AM -0700, Eric Biggers wrote:
> From: Jaegeuk Kim <jaegeuk@...nel.org>
> 
> If user has no key under an encrypted dir, fscrypt gives digested dentries.
> Previously, when looking up a dentry, f2fs only checks its hash value with
> first 4 bytes of the digested dentry, which didn't handle hash collisions fully.
> This patch enhances to check entire dentry bytes likewise ext4.
> 
> Eric reported how to reproduce this issue by:
> 
>  # seq -f "edir/abcdefghijklmnopqrstuvwxyz012345%.0f" 100000 | xargs touch
>  # find edir -type f | xargs stat -c %i | sort | uniq | wc -l
> 100000
>  # sync
>  # echo 3 > /proc/sys/vm/drop_caches
>  # keyctl new_session
>  # find edir -type f | xargs stat -c %i | sort | uniq | wc -l
> 99999
> 
> Cc: <stable@...r.kernel.org>
> Reported-by: Eric Biggers <ebiggers@...gle.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> (fixed f2fs_dentry_hash() to work even when the hash is 0)
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Thanks, applied to the fscrypt tree.

					- Ted