Re: [Qemu-devel] [PATCH V2] block/vhdx: add check for truncated image files

[Peter Lieven <pl@kamp.de>]

Am 02.09.19 um 17:24 schrieb Peter Lieven:
> qemu is currently not able to detect truncated vhdx image files.
> Add a basic check if all allocated blocks are reachable at open and
> report all errors during bdrv_co_check.
>
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
> V2: - add error reporting [Kevin]
>      - use bdrv_getlength instead of bdrv_get_allocated_file_size [Kevin]
>      - factor out BAT entry check and add error reporting for region
>        overlaps
>      - already check on vhdx_open
>
>   block/vhdx.c | 85 +++++++++++++++++++++++++++++++++++++++++-----------
>   1 file changed, 68 insertions(+), 17 deletions(-)
>
> diff --git a/block/vhdx.c b/block/vhdx.c
> index 6a09d0a55c..6afba5e8c2 100644
> --- a/block/vhdx.c
> +++ b/block/vhdx.c
> @@ -24,6 +24,7 @@
>   #include "qemu/option.h"
>   #include "qemu/crc32c.h"
>   #include "qemu/bswap.h"
> +#include "qemu/error-report.h"
>   #include "vhdx.h"
>   #include "migration/blocker.h"
>   #include "qemu/uuid.h"
> @@ -235,6 +236,9 @@ static int vhdx_region_check(BDRVVHDXState *s, uint64_t start, uint64_t length)
>       end = start + length;
>       QLIST_FOREACH(r, &s->regions, entries) {
>           if (!((start >= r->end) || (end <= r->start))) {
> +            error_report("VHDX region %" PRIu64 "-%" PRIu64 " overlaps with "
> +                         "region %" PRIu64 "-%." PRIu64, start, end, r->start,
> +                         r->end);
>               ret = -EINVAL;
>               goto exit;
>           }
> @@ -877,6 +881,60 @@ static void vhdx_calc_bat_entries(BDRVVHDXState *s)
>   
>   }
>   
> +static int vhdx_check_bat_entries(BlockDriverState *bs, int *errcnt)
> +{
> +    BDRVVHDXState *s = bs->opaque;
> +    int64_t image_file_size = bdrv_getlength(bs->file->bs);
> +    uint64_t payblocks = s->chunk_ratio;
> +    int i, ret = 0;
> +
> +    for (i = 0; i < s->bat_entries; i++) {
> +        if ((s->bat[i] & VHDX_BAT_STATE_BIT_MASK) ==
> +            PAYLOAD_BLOCK_FULLY_PRESENT) {
> +            /*
> +             * Check if fully allocated BAT entries do not reside after
> +             * end of the image file.
> +             */
> +            if ((s->bat[i] & VHDX_BAT_FILE_OFF_MASK) + s->block_size >
> +                image_file_size) {
> +                error_report("VHDX BAT entry %d offset points after end of "
> +                             "file. Image has probably been truncated.", i);
> +                ret = -EINVAL;
> +                if (!errcnt) {
> +                    break;
> +                }
> +                (*errcnt)++;
> +            }
> +
> +            /*
> +             * verify populated BAT field file offsets against
> +             * region table and log entries
> +             */
> +            if (payblocks--) {
> +                /* payload bat entries */
> +                int ret2;
> +                ret2 = vhdx_region_check(s, s->bat[i] & VHDX_BAT_FILE_OFF_MASK,
> +                                         s->block_size);
> +                if (ret2 < 0) {
> +                    ret = -EINVAL;
> +                    if (errcnt) {
> +                        break;
> +                    }


This should be if (!errcnt) ...


I will respin, but wait for feedback regarding the remainder of the patch.


Peter