On 17.12.20 17:19, Markus Armbruster wrote:
The dynamic header's size is 1024 bytes.
vpc_open() reads only the 512 bytes of the dynamic header into buf[].
Works, because it doesn't actually access the second half. However, a
colleague told me that GCC 11 warns:
../block/vpc.c:358:51: error: array subscript 'struct VHDDynDiskHeader[0]'
is partly outside array bounds of 'uint8_t[512]' [-Werror=array-bounds]
Clean up to read the full header.
Rename buf[] to dyndisk_header_buf[] while there.
Signed-off-by: Markus Armbruster <arm...@redhat.com>
---
block/vpc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/block/vpc.c b/block/vpc.c
index 1ab55f9287..2fcf3f6283 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -220,7 +220,7 @@ static int vpc_open(BlockDriverState *bs, QDict *options,
int flags,
QemuOpts *opts = NULL;
Error *local_err = NULL;
bool use_chs;
- uint8_t buf[HEADER_SIZE];
+ uint8_t dyndisk_header_buf[1024];
Perhaps this should be heap-allocated, but I don’t know whether qemu has
ever established a (perhaps just inofficial) threshold on what goes on
the stack and what goes on the heap.
uint32_t checksum;
uint64_t computed_size;
uint64_t pagetable_size;
@@ -340,14 +340,14 @@ static int vpc_open(BlockDriverState *bs, QDict *options,
int flags,
}
if (disk_type == VHD_DYNAMIC) {
- ret = bdrv_pread(bs->file, be64_to_cpu(footer->data_offset), buf,
- HEADER_SIZE);
+ ret = bdrv_pread(bs->file, be64_to_cpu(footer->data_offset),
+ dyndisk_header_buf, 1024);
sizeof() would be better, but I see that’s what patch 6 is for.
if (ret < 0) {
error_setg(errp, "Error reading dynamic VHD header");
goto fail;
}
- dyndisk_header = (VHDDynDiskHeader *) buf;
+ dyndisk_header = (VHDDynDiskHeader *)dyndisk_header_buf;
if (strncmp(dyndisk_header->magic, "cxsparse", 8)) {
error_setg(errp, "Invalid header magic");
Reviewed-by: Max Reitz <mre...@redhat.com>
