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Subject[PATCH] zram: fix invalid memory access
Date
[1] tried to fix invalid memory access on zram->disk but it didn't
fix properly because get_disk failed during module exit path.

Actually, we don't need to reset zram->disk's capacity to zero
in module exit path so that this patch introduces new argument
"reset_capacity" on zram_reset_divice and it only reset it when
reset_store is called.

[1] 6030ea9b, zram: avoid invalid memory access in zram_exit()

Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
drivers/staging/zram/zram_drv.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 7ebf91d..ebf9d6c 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -523,7 +523,7 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
return ret;
}

-static void zram_reset_device(struct zram *zram)
+static void zram_reset_device(struct zram *zram, bool reset_capacity)
{
size_t index;
struct zram_meta *meta;
@@ -552,7 +552,8 @@ static void zram_reset_device(struct zram *zram)
memset(&zram->stats, 0, sizeof(zram->stats));

zram->disksize = 0;
- set_capacity(zram->disk, 0);
+ if (reset_capacity)
+ set_capacity(zram->disk, 0);
up_write(&zram->init_lock);
}

@@ -636,7 +637,7 @@ static ssize_t reset_store(struct device *dev,
if (bdev)
fsync_bdev(bdev);

- zram_reset_device(zram);
+ zram_reset_device(zram, true);
return len;
}

@@ -903,10 +904,12 @@ static void __exit zram_exit(void)
for (i = 0; i < num_devices; i++) {
zram = &zram_devices[i];

- get_disk(zram->disk);
destroy_device(zram);
- zram_reset_device(zram);
- put_disk(zram->disk);
+ /*
+ * Shouldn't access zram->disk after destroy_device
+ * because destroy_device already released zram->disk.
+ */
+ zram_reset_device(zram, false);
}

unregister_blkdev(zram_major, "zram");
--
1.7.9.5


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