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Date:   Tue, 25 Jul 2023 23:00:43 +0530
Message-Id: <87v8e7c30c.fsf@doe.com>
From:   Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To:     Baokun Li <libaokun1@huawei.com>, linux-ext4@vger.kernel.org
Cc:     tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz,
        ojaswin@linux.ibm.com, linux-kernel@vger.kernel.org,
        yi.zhang@huawei.com, yangerkun@huawei.com, yukuai3@huawei.com,
        libaokun1@huawei.com
Subject: Re: [PATCH v2 3/3] ext4: avoid overlapping preallocations due to overflow
In-Reply-To: <20230724121059.11834-4-libaokun1@huawei.com>
Precedence: bulk

Baokun Li <libaokun1@huawei.com> writes:

> Let's say we want to allocate 2 blocks starting from 4294966386, after
> predicting the file size, start is aligned to 4294965248, len is changed
> to 2048, then end = start + size = 0x100000000. Since end is of
> type ext4_lblk_t, i.e. uint, end is truncated to 0.
>
> This causes (pa->pa_lstart >= end) to always hold when checking if the
> current extent to be allocated crosses already preallocated blocks, so the
> resulting ac_g_ex may cross already preallocated blocks. Hence we convert
> the end type to loff_t and use pa_logical_end() to avoid overflow.
>
> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> ---
>  fs/ext4/mballoc.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)

Looks good to me. Feel free to add:

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

-ritesh