Re: [Qemu-block] [PATCH 1/2] qcow2: add overlap check for bitmap directory

[Vladimir Sementsov-Ogievskiy]

29.01.2018 18:34, Max Reitz wrote:
> On 2017-11-30 17:47, Vladimir Sementsov-Ogievskiy wrote:
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> > ---
> >   block/qcow2.h          |  7 +++++--
> >   block/qcow2-refcount.c | 12 ++++++++++++
> >   block/qcow2.c          |  6 ++++++
> >   3 files changed, 23 insertions(+), 2 deletions(-)
> >
> > diff --git a/block/qcow2.h b/block/qcow2.h
> > index 6f0ff15dd0..8f226a3609 100644
> > --- a/block/qcow2.h
> > +++ b/block/qcow2.h
> > @@ -98,6 +98,7 @@
> >   #define QCOW2_OPT_OVERLAP_SNAPSHOT_TABLE "overlap-check.snapshot-table"
> >   #define QCOW2_OPT_OVERLAP_INACTIVE_L1 "overlap-check.inactive-l1"
> >   #define QCOW2_OPT_OVERLAP_INACTIVE_L2 "overlap-check.inactive-l2"
> > +#define QCOW2_OPT_OVERLAP_BITMAP_DIRECTORY "overlap-check.bitmap-directory"
> >   #define QCOW2_OPT_CACHE_SIZE "cache-size"
> >   #define QCOW2_OPT_L2_CACHE_SIZE "l2-cache-size"
> >   #define QCOW2_OPT_REFCOUNT_CACHE_SIZE "refcount-cache-size"
> > @@ -406,8 +407,9 @@ typedef enum QCow2MetadataOverlap {
> >       QCOW2_OL_SNAPSHOT_TABLE_BITNR = 5,
> >       QCOW2_OL_INACTIVE_L1_BITNR    = 6,
> >       QCOW2_OL_INACTIVE_L2_BITNR    = 7,
> > +    QCOW2_OL_BITMAP_DIRECTORY_BITNR = 8,
> >   
> > -    QCOW2_OL_MAX_BITNR            = 8,
> > +    QCOW2_OL_MAX_BITNR              = 9,
> >   
> >       QCOW2_OL_NONE           = 0,
> >       QCOW2_OL_MAIN_HEADER    = (1 << QCOW2_OL_MAIN_HEADER_BITNR),
> > @@ -420,12 +422,13 @@ typedef enum QCow2MetadataOverlap {
> >       /* NOTE: Checking overlaps with inactive L2 tables will result in bdrv
> >        * reads. */
> >       QCOW2_OL_INACTIVE_L2    = (1 << QCOW2_OL_INACTIVE_L2_BITNR),
> > +    QCOW2_OL_BITMAP_DIRECTORY = (1 << QCOW2_OL_BITMAP_DIRECTORY_BITNR),
> >   } QCow2MetadataOverlap;
> >   
> >   /* Perform all overlap checks which can be done in constant time */
> >   #define QCOW2_OL_CONSTANT \
> >       (QCOW2_OL_MAIN_HEADER | QCOW2_OL_ACTIVE_L1 | QCOW2_OL_REFCOUNT_TABLE | \
> > -     QCOW2_OL_SNAPSHOT_TABLE)
> > +     QCOW2_OL_SNAPSHOT_TABLE | QCOW2_OL_BITMAP_DIRECTORY)
> >   
> >   /* Perform all overlap checks which don't require disk access */
> >   #define QCOW2_OL_CACHED \
> > diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> > index 3de1ab51ba..a7a2703f26 100644
> > --- a/block/qcow2-refcount.c
> > +++ b/block/qcow2-refcount.c
> > @@ -2585,6 +2585,18 @@ int qcow2_check_metadata_overlap(BlockDriverState *bs, 
> > int ign, int64_t offset,
> >           }
> >       }
> >   
> > +    if ((chk & QCOW2_OL_BITMAP_DIRECTORY) &&
> > +        (s->autoclear_features & QCOW2_AUTOCLEAR_BITMAPS))
> > +    {
> > +        /* update_ext_header_and_dir_in_place firstly drop autoclear flag,
> > +         * so it will not fail */
> That's really not an argument.  bitmap_list_store() has to pass
> QCOW2_OL_BITMAP_DIRECTORY to @ign anyway.  (Because there is no reason
> not to.)

in_place is a reason. When we store directory in_place, it definitely 
overlaps with current directory.
But this is done with cleared autoclear flag (to make it safe), so we 
will skip this check and will not
fail.

> Max
>
> > +        if (overlaps_with(s->bitmap_directory_offset,
> > +                          s->bitmap_directory_size))
> > +        {
> > +            return QCOW2_OL_BITMAP_DIRECTORY;
> > +        }
> > +    }
> > +
> >       return 0;
> >   }
> >   
> > diff --git a/block/qcow2.c b/block/qcow2.c
> > index 1914a940e5..8278c0e124 100644
> > --- a/block/qcow2.c
> > +++ b/block/qcow2.c
> > @@ -655,6 +655,11 @@ static QemuOptsList qcow2_runtime_opts = {
> >               .help = "Check for unintended writes into an inactive L2 table",
> >           },
> >           {
> > +            .name = QCOW2_OPT_OVERLAP_BITMAP_DIRECTORY,
> > +            .type = QEMU_OPT_BOOL,
> > +            .help = "Check for unintended writes into the bitmap directory",
> > +        },
> > +        {
> >               .name = QCOW2_OPT_CACHE_SIZE,
> >               .type = QEMU_OPT_SIZE,
> >               .help = "Maximum combined metadata (L2 tables and refcount blocks) 
> > "
> > @@ -690,6 +695,7 @@ static const char 
> > *overlap_bool_option_names[QCOW2_OL_MAX_BITNR] = {
> >       [QCOW2_OL_SNAPSHOT_TABLE_BITNR] = QCOW2_OPT_OVERLAP_SNAPSHOT_TABLE,
> >       [QCOW2_OL_INACTIVE_L1_BITNR]    = QCOW2_OPT_OVERLAP_INACTIVE_L1,
> >       [QCOW2_OL_INACTIVE_L2_BITNR]    = QCOW2_OPT_OVERLAP_INACTIVE_L2,
> > +    [QCOW2_OL_BITMAP_DIRECTORY_BITNR] = QCOW2_OPT_OVERLAP_BITMAP_DIRECTORY,
> >   };
> >   
> >   static void cache_clean_timer_cb(void *opaque)


--
Best regards,
Vladimir