linux-kernel - [PATCH] zram: unsafe zram_get_element call in zram_read

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Message-ID: <d10cdf1d-4a67-48df-b389-3a51f60e9431@linux.dev>
Date:   Mon, 6 Nov 2023 22:54:28 +0300
From:   Vasily Averin <vasily.averin@...ux.dev>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Minchan Kim <minchan@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        zhouxianrong <zhouxianrong@...wei.com>
Subject: [PATCH] zram: unsafe zram_get_element call in zram_read_page()

Taken lock is required to access the content of zram entry.

Fixes: 8e19d540d107 ("zram: extend zero pages to same element pages")
Signed-off-by: Vasily Averin <vasily.averin@...ux.dev>
---
 drivers/block/zram/zram_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index d77d3664ca08..9ac3d4e51d26 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -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);
 	}
 
 	/* Should NEVER happen. Return bio error if it does. */
-- 
2.34.1