From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
zhouxianrong <zhouxianrong@huawei.com>,
Vasily Averin <vasily.averin@linux.dev>
Subject: Re: [PATCH] zram: unsafe zram_get_element call in zram_read_page()
Date: Tue, 7 Nov 2023 16:39:11 +0900 [thread overview]
Message-ID: <20231107073911.GB11577@google.com> (raw)
In-Reply-To: <d10cdf1d-4a67-48df-b389-3a51f60e9431@linux.dev>
On (23/11/06 22:54), Vasily Averin wrote:
> @@ -1362,14 +1362,14 @@ static int zram_read_page(struct zram *zram, struct page *page, u32 index,
> ret = zram_read_from_zspool(zram, page, index);
> zram_slot_unlock(zram, index);
> } else {
> + unsigned long entry = zram_get_element(zram, index);
> /*
> * The slot should be unlocked before reading from the backing
> * device.
> */
> zram_slot_unlock(zram, index);
>
> - ret = read_from_bdev(zram, page, zram_get_element(zram, index),
> - parent);
> + ret = read_from_bdev(zram, page, entry, parent);
Hmmm,
We may want to do more here. Basically, we probably need to re-confirm
after read_from_bdev() that the entry at index still has ZRAM_WB set
and, if so, that it points to the same blk_idx. IOW, check that it has
not been free-ed and re-used under us.
Minchan, what do you think? Is that scenario possible?
next prev parent reply other threads:[~2023-11-07 7:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-06 19:54 [PATCH] zram: unsafe zram_get_element call in zram_read_page() Vasily Averin
2023-11-07 7:39 ` Sergey Senozhatsky [this message]
2023-11-07 10:40 ` Sergey Senozhatsky
2023-11-07 18:19 ` Vasily Averin
2023-11-08 1:42 ` Sergey Senozhatsky
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