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[PATCH v3] qcow2-bitmap: Fix uint64_t left-shift overflow
From: |
Tuguoyi |
Subject: |
[PATCH v3] qcow2-bitmap: Fix uint64_t left-shift overflow |
Date: |
Wed, 30 Oct 2019 11:46:08 +0000 |
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 <address@hidden>
---
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
- [PATCH v3] qcow2-bitmap: Fix uint64_t left-shift overflow,
Tuguoyi <=