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

[Peter Lieven]

Am 03.09.19 um 15:02 schrieb Kevin Wolf:
> Am 02.09.2019 um 17:24 hat Peter Lieven geschrieben:
> > 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 <address@hidden>
> > ---
> > 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;
> bdrv_getlength() can fail. It's probably better to error out immediately
> instead of reporting that every BAT entry is > -1.
>
> > +    for (i = 0; i < s->bat_entries; i++) {
> s->bat_entries is uint32_t, so i should probably be the same.
>
> > +        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) {
> Didn't we want to introduce an overflow check before making this check?
> Something like if (bat_offset > UINT64_MAX - s->block_size)?


Sorry, i missed that.


The bat entries are UINT64_T so this check will always be false for the

default block size of 1MB. In fact we should check for


bat_offset > INT64_MAX - s->block_size


right?


Peter