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    Subject[PATCH 3.12 025/116] Staging: zram: Fix access of NULL pointer
    Date
    3.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Rashika Kheria <rashika.kheria@gmail.com>

    commit 46a51c80216cb891f271ad021f59009f34677499 upstream.

    This patch fixes the bug in reset_store caused by accessing NULL pointer.

    The bdev gets its value from bdget_disk() which could fail when memory
    pressure is severe and hence can return NULL because allocation of
    inode in bdget could fail.

    Hence, this patch introduces a check for bdev to prevent reference to a
    NULL pointer in the later part of the code. It also removes unnecessary
    check of bdev for fsync_bdev().

    Acked-by: Jerome Marchand <jmarchan@redhat.com>
    Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
    Acked-by: Minchan Kim <minchan@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/staging/zram/zram_drv.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/drivers/staging/zram/zram_drv.c
    +++ b/drivers/staging/zram/zram_drv.c
    @@ -648,6 +648,9 @@ static ssize_t reset_store(struct device
    zram = dev_to_zram(dev);
    bdev = bdget_disk(zram->disk, 0);

    + if (!bdev)
    + return -ENOMEM;
    +
    /* Do not reset an active device! */
    if (bdev->bd_holders)
    return -EBUSY;
    @@ -660,8 +663,7 @@ static ssize_t reset_store(struct device
    return -EINVAL;

    /* Make sure all pending I/O is finished */
    - if (bdev)
    - fsync_bdev(bdev);
    + fsync_bdev(bdev);

    zram_reset_device(zram, true);
    return len;



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