Commit 570542ec authored by Tuguoyi's avatar Tuguoyi Committed by Max Reitz
Browse files

qcow2-bitmap: Fix uint64_t left-shift overflow 



There are two issues in In check_constraints_on_bitmap(),
1) The sanity check on the granularity will cause uint64_t
integer left-shift overflow when cluster_size is 2M and the
granularity is BIGGER than 32K.
2) The way to calculate image size that the maximum bitmap
supported can map to is a bit incorrect.
This patch fix it by add a helper function to calculate the
number of bytes needed by a normal bitmap in image and compare
it to the maximum bitmap bytes supported by qemu.

Fixes: 5f72826e
Signed-off-by: default avatarGuoyi Tu <tu.guoyi@h3c.com>
Message-id: 4ba40cd1e7ee4a708b40899952e49f22@h3c.com
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent d0f90e14

block/qcow2-bitmap.c

+11 −3
Original line number Diff line number Diff line
@@ -142,6 +142,13 @@ static int check_table_entry(uint64_t entry, int cluster_size) 
    return 0;

}



static int64_t get_bitmap_bytes_needed(int64_t len, uint32_t granularity)

{

    int64_t num_bits = DIV_ROUND_UP(len, granularity);



    return DIV_ROUND_UP(num_bits, 8);

}



static int check_constraints_on_bitmap(BlockDriverState *bs,

                                       const char *name,

                                       uint32_t granularity,
@@ -150,6 +157,7 @@ static int check_constraints_on_bitmap(BlockDriverState *bs, 
    BDRVQcow2State *s = bs->opaque;

    int granularity_bits = ctz32(granularity);

    int64_t len = bdrv_getlength(bs);

    int64_t bitmap_bytes;



    assert(granularity > 0);

    assert((granularity & (granularity - 1)) == 0);
@@ -171,9 +179,9 @@ static int check_constraints_on_bitmap(BlockDriverState *bs, 
        return -EINVAL;

    }



    if ((len > (uint64_t)BME_MAX_PHYS_SIZE << granularity_bits) ||

        (len > (uint64_t)BME_MAX_TABLE_SIZE * s->cluster_size <<

               granularity_bits))

    bitmap_bytes = get_bitmap_bytes_needed(len, granularity);

    if ((bitmap_bytes > (uint64_t)BME_MAX_PHYS_SIZE) ||

        (bitmap_bytes > (uint64_t)BME_MAX_TABLE_SIZE * s->cluster_size))

    {

        error_setg(errp, "Too much space will be occupied by the bitmap. "

                   "Use larger granularity");