* [PATCH v3] qcow2-bitmap: Fix uint64_t left-shift overflow
@ 2019-10-30 11:46 Tuguoyi
2019-10-31 13:04 ` Vladimir Sementsov-Ogievskiy
0 siblings, 1 reply; 2+ messages in thread
From: Tuguoyi @ 2019-10-30 11:46 UTC (permalink / raw)
To: vsementsov, kwolf, mreitz, qemu-block
Cc: Chengchiwen, qemu-devel, Wangyongqing, Changlimin, Gaoliang, Wangyong
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.
Signed-off-by: Guoyi Tu <tu.guoyi@h3c.com>
---
block/qcow2-bitmap.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 98294a7..34935bb 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -142,6 +142,14 @@ static int check_table_entry(uint64_t entry, int cluster_size)
return 0;
}
+static inline 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 +158,7 @@ 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 +180,9 @@ 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");
--
2.7.4
[Patch v2]: https://lists.gnu.org/archive/html/qemu-devel/2019-10/msg07490.html
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] qcow2-bitmap: Fix uint64_t left-shift overflow
2019-10-30 11:46 [PATCH v3] qcow2-bitmap: Fix uint64_t left-shift overflow Tuguoyi
@ 2019-10-31 13:04 ` Vladimir Sementsov-Ogievskiy
0 siblings, 0 replies; 2+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2019-10-31 13:04 UTC (permalink / raw)
To: Tuguoyi, kwolf, mreitz, qemu-block
Cc: Chengchiwen, qemu-devel, Wangyongqing, Changlimin, Gaoliang, Wangyong
30.10.2019 14:46, Tuguoyi wrote:
> 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.
>
> Signed-off-by: Guoyi Tu <tu.guoyi@h3c.com>
Please, where possible, mention commit where bug was introduced in
commit message. Also, add qemu-stable@nongnu.org to CC when fixing
released bugs.
Fixes: 5f72826e7fc62167cf3a
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Thanks for fixing!
> ---
> block/qcow2-bitmap.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
> index 98294a7..34935bb 100644
> --- a/block/qcow2-bitmap.c
> +++ b/block/qcow2-bitmap.c
> @@ -142,6 +142,14 @@ static int check_table_entry(uint64_t entry, int cluster_size)
> return 0;
> }
>
> +static inline int64_t get_bitmap_bytes_needed(int64_t len,
AFAIK "inline" is no-op in this context, compiler will most probably inline it anyway,
and "inline" word don't influence on this probability. So, better drop it.
> + 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 +158,7 @@ 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 +180,9 @@ 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");
>
--
Best regards,
Vladimir
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