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    Subject[PATCH] zram: fix random data read
    Date
    fd1a30de makes a bug that it uses (struct page *) as zsmalloc's handle
    although it's a uncompressed page so that it can access random page,
    return random data or even crashed by get_first_page in zs_map_object.

    Cc: Nitin Gupta <ngupta@vflare.org>
    Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
    Cc: Jerome Marchand <jmarchan@redhat.com>
    Signed-off-by: Minchan Kim <minchan@kernel.org>
    ---
    drivers/staging/zram/zram_drv.c | 15 ++++++++-------
    1 file changed, 8 insertions(+), 7 deletions(-)

    diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
    index abd69d1..0cdc303 100644
    --- a/drivers/staging/zram/zram_drv.c
    +++ b/drivers/staging/zram/zram_drv.c
    @@ -280,26 +280,27 @@ static int zram_read_before_write(struct zram *zram, char *mem, u32 index)
    size_t clen = PAGE_SIZE;
    struct zobj_header *zheader;
    unsigned char *cmem;
    + unsigned long handle = zram->table[index].handle;

    - if (zram_test_flag(zram, index, ZRAM_ZERO) ||
    - !zram->table[index].handle) {
    + if (zram_test_flag(zram, index, ZRAM_ZERO) || !handle) {
    memset(mem, 0, PAGE_SIZE);
    return 0;
    }

    - cmem = zs_map_object(zram->mem_pool, zram->table[index].handle);
    -
    /* Page is stored uncompressed since it's incompressible */
    if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
    - memcpy(mem, cmem, PAGE_SIZE);
    - kunmap_atomic(cmem);
    + char *src = kmap_atomic((struct page *)handle);
    + memcpy(mem, src, PAGE_SIZE);
    + kunmap_atomic(src);
    return 0;
    }

    + cmem = zs_map_object(zram->mem_pool, handle);
    +
    ret = lzo1x_decompress_safe(cmem + sizeof(*zheader),
    zram->table[index].size,
    mem, &clen);
    - zs_unmap_object(zram->mem_pool, zram->table[index].handle);
    + zs_unmap_object(zram->mem_pool, handle);

    /* Should NEVER happen. Return bio error if it does. */
    if (unlikely(ret != LZO_E_OK)) {
    --
    1.7.9.5


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