[PATCH v4 00/10] qcow2 check: check some reserved bits and subcluster bitmaps

[PATCH v4 00/10] qcow2 check: check some reserved bits and subcluster bitmaps

[Vladimir Sementsov-Ogievskiy]

Hi all!

Here are some good refactorings and new (qemu-img check) checks for
qcow2.

06  qcow2-refcount: check_refcounts_l2(): check l2_bitmap
      don't fix unallocated cluster with allocated subclusters (no strong opinion how to do it correctly)
      drop Eric's r-b
      keep Kirill's t-b (I believe it still applies, my original task didn't include error fixing)
      define l2_bitmap near l2_entry
      add separate assertion and "break;" for QCOW2_CLUSTER_ZERO_PLAIN
others: add r-b: Hanna


Vladimir Sementsov-Ogievskiy (10):
  qcow2-refcount: improve style of check_refcounts_l2()
  qcow2: compressed read: simplify cluster descriptor passing
  qcow2: introduce qcow2_parse_compressed_l2_entry() helper
  qcow2-refcount: introduce fix_l2_entry_by_zero()
  qcow2-refcount: fix_l2_entry_by_zero(): also zero L2 entry bitmap
  qcow2-refcount: check_refcounts_l2(): check l2_bitmap
  qcow2-refcount: check_refcounts_l2(): check reserved bits
  qcow2-refcount: improve style of check_refcounts_l1()
  qcow2-refcount: check_refcounts_l1(): check reserved bits
  qcow2-refcount: check_refblocks(): add separate message for reserved

 block/qcow2.h          |   7 +-
 block/qcow2-cluster.c  |  20 ++-
 block/qcow2-refcount.c | 324 ++++++++++++++++++++++++++---------------
 block/qcow2.c          |  13 +-
 4 files changed, 236 insertions(+), 128 deletions(-)

-- 
2.29.2

[PATCH v4 01/10] qcow2-refcount: improve style of check_refcounts_l2()

[Vladimir Sementsov-Ogievskiy]

 - don't use same name for size in bytes and in entries
 - use g_autofree for l2_table
 - add whitespace
 - fix block comment style

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2-refcount.c | 47 +++++++++++++++++++++---------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 8e649b008e..2734338625 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1601,23 +1601,22 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                               int flags, BdrvCheckMode fix, bool active)
 {
     BDRVQcow2State *s = bs->opaque;
-    uint64_t *l2_table, l2_entry;
+    uint64_t l2_entry;
     uint64_t next_contiguous_offset = 0;
-    int i, l2_size, nb_csectors, ret;
+    int i, nb_csectors, ret;
+    size_t l2_size_bytes = s->l2_size * l2_entry_size(s);
+    g_autofree uint64_t *l2_table = g_malloc(l2_size_bytes);
 
     /* Read L2 table from disk */
-    l2_size = s->l2_size * l2_entry_size(s);
-    l2_table = g_malloc(l2_size);
-
-    ret = bdrv_pread(bs->file, l2_offset, l2_table, l2_size);
+    ret = bdrv_pread(bs->file, l2_offset, l2_table, l2_size_bytes);
     if (ret < 0) {
         fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n");
         res->check_errors++;
-        goto fail;
+        return ret;
     }
 
     /* Do the actual checks */
-    for(i = 0; i < s->l2_size; i++) {
+    for (i = 0; i < s->l2_size; i++) {
         l2_entry = get_l2_entry(s, l2_table, i);
 
         switch (qcow2_get_cluster_type(bs, l2_entry)) {
@@ -1647,14 +1646,15 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                 l2_entry & QCOW2_COMPRESSED_SECTOR_MASK,
                 nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE);
             if (ret < 0) {
-                goto fail;
+                return ret;
             }
 
             if (flags & CHECK_FRAG_INFO) {
                 res->bfi.allocated_clusters++;
                 res->bfi.compressed_clusters++;
 
-                /* Compressed clusters are fragmented by nature.  Since they
+                /*
+                 * Compressed clusters are fragmented by nature.  Since they
                  * take up sub-sector space but we only have sector granularity
                  * I/O we need to re-read the same sectors even for adjacent
                  * compressed clusters.
@@ -1700,9 +1700,11 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                         if (ret < 0) {
                             fprintf(stderr, "ERROR: Overlap check failed\n");
                             res->check_errors++;
-                            /* Something is seriously wrong, so abort checking
-                             * this L2 table */
-                            goto fail;
+                            /*
+                             * Something is seriously wrong, so abort checking
+                             * this L2 table.
+                             */
+                            return ret;
                         }
 
                         ret = bdrv_pwrite_sync(bs->file, l2e_offset,
@@ -1712,13 +1714,17 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                             fprintf(stderr, "ERROR: Failed to overwrite L2 "
                                     "table entry: %s\n", strerror(-ret));
                             res->check_errors++;
-                            /* Do not abort, continue checking the rest of this
-                             * L2 table's entries */
+                            /*
+                             * Do not abort, continue checking the rest of this
+                             * L2 table's entries.
+                             */
                         } else {
                             res->corruptions--;
                             res->corruptions_fixed++;
-                            /* Skip marking the cluster as used
-                             * (it is unused now) */
+                            /*
+                             * Skip marking the cluster as used
+                             * (it is unused now).
+                             */
                             continue;
                         }
                     }
@@ -1743,7 +1749,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                                                refcount_table_size,
                                                offset, s->cluster_size);
                 if (ret < 0) {
-                    goto fail;
+                    return ret;
                 }
             }
             break;
@@ -1758,12 +1764,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         }
     }
 
-    g_free(l2_table);
     return 0;
-
-fail:
-    g_free(l2_table);
-    return ret;
 }
 
 /*
-- 
2.29.2

[PATCH v4 02/10] qcow2: compressed read: simplify cluster descriptor passing

[Vladimir Sementsov-Ogievskiy]

Let's pass the whole L2 entry and not bother with
L2E_COMPRESSED_OFFSET_SIZE_MASK.

It also helps further refactoring that adds generic
qcow2_parse_compressed_l2_entry() helper.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2.h         |  1 -
 block/qcow2-cluster.c |  5 ++---
 block/qcow2.c         | 12 +++++++-----
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 0fe5f74ed3..42a0058ab7 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -588,7 +588,6 @@ typedef enum QCow2MetadataOverlap {
 
 #define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
 #define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
-#define L2E_COMPRESSED_OFFSET_SIZE_MASK 0x3fffffffffffffffULL
 
 #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
 
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index bd0597842f..04735ee439 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -556,8 +556,7 @@ static int coroutine_fn do_perform_cow_write(BlockDriverState *bs,
  * offset needs to be aligned to a cluster boundary.
  *
  * If the cluster is unallocated then *host_offset will be 0.
- * If the cluster is compressed then *host_offset will contain the
- * complete compressed cluster descriptor.
+ * If the cluster is compressed then *host_offset will contain the l2 entry.
  *
  * On entry, *bytes is the maximum number of contiguous bytes starting at
  * offset that we are interested in.
@@ -660,7 +659,7 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
             ret = -EIO;
             goto fail;
         }
-        *host_offset = l2_entry & L2E_COMPRESSED_OFFSET_SIZE_MASK;
+        *host_offset = l2_entry;
         break;
     case QCOW2_SUBCLUSTER_ZERO_PLAIN:
     case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
diff --git a/block/qcow2.c b/block/qcow2.c
index 9f1b6461c8..e5d8ab679e 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -74,7 +74,7 @@ typedef struct {
 
 static int coroutine_fn
 qcow2_co_preadv_compressed(BlockDriverState *bs,
-                           uint64_t cluster_descriptor,
+                           uint64_t l2_entry,
                            uint64_t offset,
                            uint64_t bytes,
                            QEMUIOVector *qiov,
@@ -2205,7 +2205,7 @@ typedef struct Qcow2AioTask {
 
     BlockDriverState *bs;
     QCow2SubclusterType subcluster_type; /* only for read */
-    uint64_t host_offset; /* or full descriptor in compressed clusters */
+    uint64_t host_offset; /* or l2_entry for compressed read */
     uint64_t offset;
     uint64_t bytes;
     QEMUIOVector *qiov;
@@ -4693,7 +4693,7 @@ qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
 
 static int coroutine_fn
 qcow2_co_preadv_compressed(BlockDriverState *bs,
-                           uint64_t cluster_descriptor,
+                           uint64_t l2_entry,
                            uint64_t offset,
                            uint64_t bytes,
                            QEMUIOVector *qiov,
@@ -4705,8 +4705,10 @@ qcow2_co_preadv_compressed(BlockDriverState *bs,
     uint8_t *buf, *out_buf;
     int offset_in_cluster = offset_into_cluster(s, offset);
 
-    coffset = cluster_descriptor & s->cluster_offset_mask;
-    nb_csectors = ((cluster_descriptor >> s->csize_shift) & s->csize_mask) + 1;
+    assert(qcow2_get_cluster_type(bs, l2_entry) == QCOW2_CLUSTER_COMPRESSED);
+
+    coffset = l2_entry & s->cluster_offset_mask;
+    nb_csectors = ((l2_entry >> s->csize_shift) & s->csize_mask) + 1;
     csize = nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE -
         (coffset & ~QCOW2_COMPRESSED_SECTOR_MASK);
 
-- 
2.29.2

[PATCH v4 03/10] qcow2: introduce qcow2_parse_compressed_l2_entry() helper

[Vladimir Sementsov-Ogievskiy]

Add helper to parse compressed l2_entry and use it everywhere instead
of open-coding.

Note, that in most places we move to precise coffset/csize instead of
sector-aligned. Still it should work good enough for updating
refcounts.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2.h          |  3 ++-
 block/qcow2-cluster.c  | 15 +++++++++++++++
 block/qcow2-refcount.c | 36 +++++++++++++++++-------------------
 block/qcow2.c          |  9 ++-------
 4 files changed, 36 insertions(+), 27 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 42a0058ab7..c0e1e83796 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -110,7 +110,6 @@
 
 /* Defined in the qcow2 spec (compressed cluster descriptor) */
 #define QCOW2_COMPRESSED_SECTOR_SIZE 512U
-#define QCOW2_COMPRESSED_SECTOR_MASK (~(QCOW2_COMPRESSED_SECTOR_SIZE - 1ULL))
 
 /* Must be at least 2 to cover COW */
 #define MIN_L2_CACHE_SIZE 2 /* cache entries */
@@ -913,6 +912,8 @@ int qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
                                           uint64_t offset,
                                           int compressed_size,
                                           uint64_t *host_offset);
+void qcow2_parse_compressed_l2_entry(BlockDriverState *bs, uint64_t l2_entry,
+                                     uint64_t *coffset, int *csize);
 
 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m);
 void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m);
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 04735ee439..70d0570a33 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -2462,3 +2462,18 @@ fail:
     g_free(l1_table);
     return ret;
 }
+
+void qcow2_parse_compressed_l2_entry(BlockDriverState *bs, uint64_t l2_entry,
+                                     uint64_t *coffset, int *csize)
+{
+    BDRVQcow2State *s = bs->opaque;
+    int nb_csectors;
+
+    assert(qcow2_get_cluster_type(bs, l2_entry) == QCOW2_CLUSTER_COMPRESSED);
+
+    *coffset = l2_entry & s->cluster_offset_mask;
+
+    nb_csectors = ((l2_entry >> s->csize_shift) & s->csize_mask) + 1;
+    *csize = nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE -
+        (*coffset & (QCOW2_COMPRESSED_SECTOR_SIZE - 1));
+}
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 2734338625..66cbb94ef9 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1177,11 +1177,11 @@ void qcow2_free_any_cluster(BlockDriverState *bs, uint64_t l2_entry,
     switch (ctype) {
     case QCOW2_CLUSTER_COMPRESSED:
         {
-            int64_t offset = (l2_entry & s->cluster_offset_mask)
-                & QCOW2_COMPRESSED_SECTOR_MASK;
-            int size = QCOW2_COMPRESSED_SECTOR_SIZE *
-                (((l2_entry >> s->csize_shift) & s->csize_mask) + 1);
-            qcow2_free_clusters(bs, offset, size, type);
+            uint64_t coffset;
+            int csize;
+
+            qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
+            qcow2_free_clusters(bs, coffset, csize, type);
         }
         break;
     case QCOW2_CLUSTER_NORMAL:
@@ -1247,7 +1247,7 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
     bool l1_allocated = false;
     int64_t old_entry, old_l2_offset;
     unsigned slice, slice_size2, n_slices;
-    int i, j, l1_modified = 0, nb_csectors;
+    int i, j, l1_modified = 0;
     int ret;
 
     assert(addend >= -1 && addend <= 1);
@@ -1318,14 +1318,14 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
 
                     switch (qcow2_get_cluster_type(bs, entry)) {
                     case QCOW2_CLUSTER_COMPRESSED:
-                        nb_csectors = ((entry >> s->csize_shift) &
-                                       s->csize_mask) + 1;
                         if (addend != 0) {
-                            uint64_t coffset = (entry & s->cluster_offset_mask)
-                                & QCOW2_COMPRESSED_SECTOR_MASK;
+                            uint64_t coffset;
+                            int csize;
+
+                            qcow2_parse_compressed_l2_entry(bs, entry,
+                                                            &coffset, &csize);
                             ret = update_refcount(
-                                bs, coffset,
-                                nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE,
+                                bs, coffset, csize,
                                 abs(addend), addend < 0,
                                 QCOW2_DISCARD_SNAPSHOT);
                             if (ret < 0) {
@@ -1603,7 +1603,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
     BDRVQcow2State *s = bs->opaque;
     uint64_t l2_entry;
     uint64_t next_contiguous_offset = 0;
-    int i, nb_csectors, ret;
+    int i, ret;
     size_t l2_size_bytes = s->l2_size * l2_entry_size(s);
     g_autofree uint64_t *l2_table = g_malloc(l2_size_bytes);
 
@@ -1617,6 +1617,8 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
 
     /* Do the actual checks */
     for (i = 0; i < s->l2_size; i++) {
+        uint64_t coffset;
+        int csize;
         l2_entry = get_l2_entry(s, l2_table, i);
 
         switch (qcow2_get_cluster_type(bs, l2_entry)) {
@@ -1638,13 +1640,9 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
             }
 
             /* Mark cluster as used */
-            nb_csectors = ((l2_entry >> s->csize_shift) &
-                           s->csize_mask) + 1;
-            l2_entry &= s->cluster_offset_mask;
+            qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
             ret = qcow2_inc_refcounts_imrt(
-                bs, res, refcount_table, refcount_table_size,
-                l2_entry & QCOW2_COMPRESSED_SECTOR_MASK,
-                nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE);
+                bs, res, refcount_table, refcount_table_size, coffset, csize);
             if (ret < 0) {
                 return ret;
             }
diff --git a/block/qcow2.c b/block/qcow2.c
index e5d8ab679e..02f9f3e636 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4700,17 +4700,12 @@ qcow2_co_preadv_compressed(BlockDriverState *bs,
                            size_t qiov_offset)
 {
     BDRVQcow2State *s = bs->opaque;
-    int ret = 0, csize, nb_csectors;
+    int ret = 0, csize;
     uint64_t coffset;
     uint8_t *buf, *out_buf;
     int offset_in_cluster = offset_into_cluster(s, offset);
 
-    assert(qcow2_get_cluster_type(bs, l2_entry) == QCOW2_CLUSTER_COMPRESSED);
-
-    coffset = l2_entry & s->cluster_offset_mask;
-    nb_csectors = ((l2_entry >> s->csize_shift) & s->csize_mask) + 1;
-    csize = nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE -
-        (coffset & ~QCOW2_COMPRESSED_SECTOR_MASK);
+    qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
 
     buf = g_try_malloc(csize);
     if (!buf) {
-- 
2.29.2

[PATCH v4 04/10] qcow2-refcount: introduce fix_l2_entry_by_zero()

[Vladimir Sementsov-Ogievskiy]

Split fix_l2_entry_by_zero() out of check_refcounts_l2() to be
reused in further patch.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2-refcount.c | 87 +++++++++++++++++++++++++++++-------------
 1 file changed, 60 insertions(+), 27 deletions(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 66cbb94ef9..184b96ad63 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1587,6 +1587,54 @@ enum {
     CHECK_FRAG_INFO = 0x2,      /* update BlockFragInfo counters */
 };
 
+/*
+ * Fix L2 entry by making it QCOW2_CLUSTER_ZERO_PLAIN.
+ *
+ * This function decrements res->corruptions on success, so the caller is
+ * responsible to increment res->corruptions prior to the call.
+ *
+ * On failure in-memory @l2_table may be modified.
+ */
+static int fix_l2_entry_by_zero(BlockDriverState *bs, BdrvCheckResult *res,
+                                uint64_t l2_offset,
+                                uint64_t *l2_table, int l2_index, bool active,
+                                bool *metadata_overlap)
+{
+    BDRVQcow2State *s = bs->opaque;
+    int ret;
+    int idx = l2_index * (l2_entry_size(s) / sizeof(uint64_t));
+    uint64_t l2e_offset = l2_offset + (uint64_t)l2_index * l2_entry_size(s);
+    int ign = active ? QCOW2_OL_ACTIVE_L2 : QCOW2_OL_INACTIVE_L2;
+    uint64_t l2_entry = has_subclusters(s) ? 0 : QCOW_OFLAG_ZERO;
+
+    set_l2_entry(s, l2_table, l2_index, l2_entry);
+    ret = qcow2_pre_write_overlap_check(bs, ign, l2e_offset, l2_entry_size(s),
+                                        false);
+    if (metadata_overlap) {
+        *metadata_overlap = ret < 0;
+    }
+    if (ret < 0) {
+        fprintf(stderr, "ERROR: Overlap check failed\n");
+        goto fail;
+    }
+
+    ret = bdrv_pwrite_sync(bs->file, l2e_offset, &l2_table[idx],
+                           l2_entry_size(s));
+    if (ret < 0) {
+        fprintf(stderr, "ERROR: Failed to overwrite L2 "
+                "table entry: %s\n", strerror(-ret));
+        goto fail;
+    }
+
+    res->corruptions--;
+    res->corruptions_fixed++;
+    return 0;
+
+fail:
+    res->check_errors++;
+    return ret;
+}
+
 /*
  * Increases the refcount in the given refcount table for the all clusters
  * referenced in the L2 table. While doing so, performs some checks on L2
@@ -1606,6 +1654,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
     int i, ret;
     size_t l2_size_bytes = s->l2_size * l2_entry_size(s);
     g_autofree uint64_t *l2_table = g_malloc(l2_size_bytes);
+    bool metadata_overlap;
 
     /* Read L2 table from disk */
     ret = bdrv_pread(bs->file, l2_offset, l2_table, l2_size_bytes);
@@ -1685,19 +1734,10 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                             fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR",
                             offset);
                     if (fix & BDRV_FIX_ERRORS) {
-                        int idx = i * (l2_entry_size(s) / sizeof(uint64_t));
-                        uint64_t l2e_offset =
-                            l2_offset + (uint64_t)i * l2_entry_size(s);
-                        int ign = active ? QCOW2_OL_ACTIVE_L2 :
-                                           QCOW2_OL_INACTIVE_L2;
-
-                        l2_entry = has_subclusters(s) ? 0 : QCOW_OFLAG_ZERO;
-                        set_l2_entry(s, l2_table, i, l2_entry);
-                        ret = qcow2_pre_write_overlap_check(bs, ign,
-                                l2e_offset, l2_entry_size(s), false);
-                        if (ret < 0) {
-                            fprintf(stderr, "ERROR: Overlap check failed\n");
-                            res->check_errors++;
+                        ret = fix_l2_entry_by_zero(bs, res, l2_offset,
+                                                   l2_table, i, active,
+                                                   &metadata_overlap);
+                        if (metadata_overlap) {
                             /*
                              * Something is seriously wrong, so abort checking
                              * this L2 table.
@@ -1705,26 +1745,19 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                             return ret;
                         }
 
-                        ret = bdrv_pwrite_sync(bs->file, l2e_offset,
-                                               &l2_table[idx],
-                                               l2_entry_size(s));
-                        if (ret < 0) {
-                            fprintf(stderr, "ERROR: Failed to overwrite L2 "
-                                    "table entry: %s\n", strerror(-ret));
-                            res->check_errors++;
-                            /*
-                             * Do not abort, continue checking the rest of this
-                             * L2 table's entries.
-                             */
-                        } else {
-                            res->corruptions--;
-                            res->corruptions_fixed++;
+                        if (ret == 0) {
                             /*
                              * Skip marking the cluster as used
                              * (it is unused now).
                              */
                             continue;
                         }
+
+                        /*
+                         * Failed to fix.
+                         * Do not abort, continue checking the rest of this
+                         * L2 table's entries.
+                         */
                     }
                 } else {
                     fprintf(stderr, "ERROR offset=%" PRIx64 ": Data cluster is "
-- 
2.29.2

[PATCH v4 05/10] qcow2-refcount: fix_l2_entry_by_zero(): also zero L2 entry bitmap

[Vladimir Sementsov-Ogievskiy]

We'll reuse the function to fix wrong L2 entry bitmap. Support it now.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2-refcount.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 184b96ad63..f48c5e1b5d 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1588,7 +1588,8 @@ enum {
 };
 
 /*
- * Fix L2 entry by making it QCOW2_CLUSTER_ZERO_PLAIN.
+ * Fix L2 entry by making it QCOW2_CLUSTER_ZERO_PLAIN (or making all its present
+ * subclusters QCOW2_SUBCLUSTER_ZERO_PLAIN).
  *
  * This function decrements res->corruptions on success, so the caller is
  * responsible to increment res->corruptions prior to the call.
@@ -1605,9 +1606,20 @@ static int fix_l2_entry_by_zero(BlockDriverState *bs, BdrvCheckResult *res,
     int idx = l2_index * (l2_entry_size(s) / sizeof(uint64_t));
     uint64_t l2e_offset = l2_offset + (uint64_t)l2_index * l2_entry_size(s);
     int ign = active ? QCOW2_OL_ACTIVE_L2 : QCOW2_OL_INACTIVE_L2;
-    uint64_t l2_entry = has_subclusters(s) ? 0 : QCOW_OFLAG_ZERO;
 
-    set_l2_entry(s, l2_table, l2_index, l2_entry);
+    if (has_subclusters(s)) {
+        uint64_t l2_bitmap = get_l2_bitmap(s, l2_table, l2_index);
+
+        /* Allocated subclusters become zero */
+        l2_bitmap |= l2_bitmap << 32;
+        l2_bitmap &= QCOW_L2_BITMAP_ALL_ZEROES;
+
+        set_l2_bitmap(s, l2_table, l2_index, l2_bitmap);
+        set_l2_entry(s, l2_table, l2_index, 0);
+    } else {
+        set_l2_entry(s, l2_table, l2_index, QCOW_OFLAG_ZERO);
+    }
+
     ret = qcow2_pre_write_overlap_check(bs, ign, l2e_offset, l2_entry_size(s),
                                         false);
     if (metadata_overlap) {
-- 
2.29.2

[PATCH v4 06/10] qcow2-refcount: check_refcounts_l2(): check l2_bitmap

[Vladimir Sementsov-Ogievskiy]

Check subcluster bitmap of the l2 entry for different types of
clusters:

 - for compressed it must be zero
 - for allocated check consistency of two parts of the bitmap
 - for unallocated all subclusters should be unallocated
   (or zero-plain)

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 block/qcow2-refcount.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index f48c5e1b5d..9a5ae3cac4 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1661,7 +1661,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                               int flags, BdrvCheckMode fix, bool active)
 {
     BDRVQcow2State *s = bs->opaque;
-    uint64_t l2_entry;
+    uint64_t l2_entry, l2_bitmap;
     uint64_t next_contiguous_offset = 0;
     int i, ret;
     size_t l2_size_bytes = s->l2_size * l2_entry_size(s);
@@ -1681,6 +1681,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         uint64_t coffset;
         int csize;
         l2_entry = get_l2_entry(s, l2_table, i);
+        l2_bitmap = get_l2_bitmap(s, l2_table, i);
 
         switch (qcow2_get_cluster_type(bs, l2_entry)) {
         case QCOW2_CLUSTER_COMPRESSED:
@@ -1700,6 +1701,14 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                 break;
             }
 
+            if (l2_bitmap) {
+                fprintf(stderr, "ERROR compressed cluster %d with non-zero "
+                        "subcluster allocation bitmap, entry=0x%" PRIx64 "\n",
+                        i, l2_entry);
+                res->corruptions++;
+                break;
+            }
+
             /* Mark cluster as used */
             qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
             ret = qcow2_inc_refcounts_imrt(
@@ -1727,13 +1736,19 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         {
             uint64_t offset = l2_entry & L2E_OFFSET_MASK;
 
+            if ((l2_bitmap >> 32) & l2_bitmap) {
+                res->corruptions++;
+                fprintf(stderr, "ERROR offset=%" PRIx64 ": Allocated "
+                        "cluster has corrupted subcluster allocation bitmap\n",
+                        offset);
+            }
+
             /* Correct offsets are cluster aligned */
             if (offset_into_cluster(s, offset)) {
                 bool contains_data;
                 res->corruptions++;
 
                 if (has_subclusters(s)) {
-                    uint64_t l2_bitmap = get_l2_bitmap(s, l2_table, i);
                     contains_data = (l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC);
                 } else {
                     contains_data = !(l2_entry & QCOW_OFLAG_ZERO);
@@ -1799,7 +1814,16 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         }
 
         case QCOW2_CLUSTER_ZERO_PLAIN:
+            /* Impossible when image has subclusters */
+            assert(!l2_bitmap);
+            break;
+
         case QCOW2_CLUSTER_UNALLOCATED:
+            if (l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC) {
+                res->corruptions++;
+                fprintf(stderr, "ERROR: Unallocated "
+                        "cluster has non-zero subcluster allocation map\n");
+            }
             break;
 
         default:
-- 
2.29.2

Re: [PATCH v4 06/10] qcow2-refcount: check_refcounts_l2(): check l2_bitmap

[Eric Blake]

On Tue, Sep 14, 2021 at 03:24:50PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Check subcluster bitmap of the l2 entry for different types of
> clusters:
> 
>  - for compressed it must be zero
>  - for allocated check consistency of two parts of the bitmap
>  - for unallocated all subclusters should be unallocated
>    (or zero-plain)
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> ---
>  block/qcow2-refcount.c | 28 ++++++++++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
>

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v4 06/10] qcow2-refcount: check_refcounts_l2(): check l2_bitmap

[Vladimir Sementsov-Ogievskiy]

14.09.2021 17:25, Eric Blake wrote:
> On Tue, Sep 14, 2021 at 03:24:50PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Check subcluster bitmap of the l2 entry for different types of
>> clusters:
>>
>>   - for compressed it must be zero
>>   - for allocated check consistency of two parts of the bitmap
>>   - for unallocated all subclusters should be unallocated
>>     (or zero-plain)
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
>> ---
>>   block/qcow2-refcount.c | 28 ++++++++++++++++++++++++++--
>>   1 file changed, 26 insertions(+), 2 deletions(-)
>>
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 

Thanks!

-- 
Best regards,
Vladimir

Re: [PATCH v4 06/10] qcow2-refcount: check_refcounts_l2(): check l2_bitmap

[Hanna Reitz]

On 14.09.21 14:24, Vladimir Sementsov-Ogievskiy wrote:
> Check subcluster bitmap of the l2 entry for different types of
> clusters:
>
>   - for compressed it must be zero
>   - for allocated check consistency of two parts of the bitmap
>   - for unallocated all subclusters should be unallocated
>     (or zero-plain)
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> ---
>   block/qcow2-refcount.c | 28 ++++++++++++++++++++++++++--
>   1 file changed, 26 insertions(+), 2 deletions(-)

Reviewed-by: Hanna Reitz <hreitz@redhat.com>

[PATCH v4 07/10] qcow2-refcount: check_refcounts_l2(): check reserved bits

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2.h          |  1 +
 block/qcow2-refcount.c | 12 +++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index c0e1e83796..b8b1093b61 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -587,6 +587,7 @@ typedef enum QCow2MetadataOverlap {
 
 #define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
 #define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
+#define L2E_STD_RESERVED_MASK 0x3f000000000001feULL
 
 #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
 
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 9a5ae3cac4..5d57e677bc 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1682,8 +1682,18 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         int csize;
         l2_entry = get_l2_entry(s, l2_table, i);
         l2_bitmap = get_l2_bitmap(s, l2_table, i);
+        QCow2ClusterType type = qcow2_get_cluster_type(bs, l2_entry);
 
-        switch (qcow2_get_cluster_type(bs, l2_entry)) {
+        if (type != QCOW2_CLUSTER_COMPRESSED) {
+            /* Check reserved bits of Standard Cluster Descriptor */
+            if (l2_entry & L2E_STD_RESERVED_MASK) {
+                fprintf(stderr, "ERROR found l2 entry with reserved bits set: "
+                        "%" PRIx64 "\n", l2_entry);
+                res->corruptions++;
+            }
+        }
+
+        switch (type) {
         case QCOW2_CLUSTER_COMPRESSED:
             /* Compressed clusters don't have QCOW_OFLAG_COPIED */
             if (l2_entry & QCOW_OFLAG_COPIED) {
-- 
2.29.2

Re: [PATCH v4 07/10] qcow2-refcount: check_refcounts_l2(): check reserved bits

[Hanna Reitz]

On 14.09.21 14:24, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> Reviewed-by: Hanna Reitz <hreitz@redhat.com>
> ---
>   block/qcow2.h          |  1 +
>   block/qcow2-refcount.c | 12 +++++++++++-
>   2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/block/qcow2.h b/block/qcow2.h
> index c0e1e83796..b8b1093b61 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -587,6 +587,7 @@ typedef enum QCow2MetadataOverlap {
>   
>   #define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
>   #define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
> +#define L2E_STD_RESERVED_MASK 0x3f000000000001feULL
>   
>   #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
>   
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index 9a5ae3cac4..5d57e677bc 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -1682,8 +1682,18 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
>           int csize;
>           l2_entry = get_l2_entry(s, l2_table, i);
>           l2_bitmap = get_l2_bitmap(s, l2_table, i);
> +        QCow2ClusterType type = qcow2_get_cluster_type(bs, l2_entry);

Hm, with l2_bitmap being declared next to l2_entry, this is now the 
patch that adds a declaration after a statement here.

(The possible resolutions seem to be the same, either move the 
declaration up to the function’s root block, or move l2_entry and 
l2_bitmap’s declarations here...)

(I don’t think we need a v5 for this, it should be fine if you tell me 
which way you prefer.)

Hanna

Re: [PATCH v4 07/10] qcow2-refcount: check_refcounts_l2(): check reserved bits

[Vladimir Sementsov-Ogievskiy]

14.09.2021 20:15, Hanna Reitz wrote:
> On 14.09.21 14:24, Vladimir Sementsov-Ogievskiy wrote:
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
>> Reviewed-by: Hanna Reitz <hreitz@redhat.com>
>> ---
>>   block/qcow2.h          |  1 +
>>   block/qcow2-refcount.c | 12 +++++++++++-
>>   2 files changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/qcow2.h b/block/qcow2.h
>> index c0e1e83796..b8b1093b61 100644
>> --- a/block/qcow2.h
>> +++ b/block/qcow2.h
>> @@ -587,6 +587,7 @@ typedef enum QCow2MetadataOverlap {
>>   #define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
>>   #define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
>> +#define L2E_STD_RESERVED_MASK 0x3f000000000001feULL
>>   #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
>> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
>> index 9a5ae3cac4..5d57e677bc 100644
>> --- a/block/qcow2-refcount.c
>> +++ b/block/qcow2-refcount.c
>> @@ -1682,8 +1682,18 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
>>           int csize;
>>           l2_entry = get_l2_entry(s, l2_table, i);
>>           l2_bitmap = get_l2_bitmap(s, l2_table, i);
>> +        QCow2ClusterType type = qcow2_get_cluster_type(bs, l2_entry);

Oh :(

> 
> Hm, with l2_bitmap being declared next to l2_entry, this is now the patch that adds a declaration after a statement here.
> 
> (The possible resolutions seem to be the same, either move the declaration up to the function’s root block, or move l2_entry and l2_bitmap’s declarations here...)
> 
> (I don’t think we need a v5 for this, it should be fine if you tell me which way you prefer.)
> 

I'd keep type here:

QCow2ClusterType type;

l2_entry = ...
l2_bitmap = ...
type = qcow2_get_cluster_type(bs, l2_entry);


-- 
Best regards,
Vladimir

[PATCH v4 08/10] qcow2-refcount: improve style of check_refcounts_l1()

[Vladimir Sementsov-Ogievskiy]

 - use g_autofree for l1_table
 - better name for size in bytes variable
 - reduce code blocks nesting
 - whitespaces, braces, newlines

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2-refcount.c | 98 +++++++++++++++++++++---------------------
 1 file changed, 50 insertions(+), 48 deletions(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 5d57e677bc..153e5ca087 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1860,71 +1860,73 @@ static int check_refcounts_l1(BlockDriverState *bs,
                               int flags, BdrvCheckMode fix, bool active)
 {
     BDRVQcow2State *s = bs->opaque;
-    uint64_t *l1_table = NULL, l2_offset, l1_size2;
+    size_t l1_size_bytes = l1_size * L1E_SIZE;
+    g_autofree uint64_t *l1_table = NULL;
+    uint64_t l2_offset;
     int i, ret;
 
-    l1_size2 = l1_size * L1E_SIZE;
+    if (!l1_size) {
+        return 0;
+    }
 
     /* Mark L1 table as used */
     ret = qcow2_inc_refcounts_imrt(bs, res, refcount_table, refcount_table_size,
-                                   l1_table_offset, l1_size2);
+                                   l1_table_offset, l1_size_bytes);
     if (ret < 0) {
-        goto fail;
+        return ret;
+    }
+
+    l1_table = g_try_malloc(l1_size_bytes);
+    if (l1_table == NULL) {
+        res->check_errors++;
+        return -ENOMEM;
     }
 
     /* Read L1 table entries from disk */
-    if (l1_size2 > 0) {
-        l1_table = g_try_malloc(l1_size2);
-        if (l1_table == NULL) {
-            ret = -ENOMEM;
-            res->check_errors++;
-            goto fail;
-        }
-        ret = bdrv_pread(bs->file, l1_table_offset, l1_table, l1_size2);
-        if (ret < 0) {
-            fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
-            res->check_errors++;
-            goto fail;
-        }
-        for(i = 0;i < l1_size; i++)
-            be64_to_cpus(&l1_table[i]);
+    ret = bdrv_pread(bs->file, l1_table_offset, l1_table, l1_size_bytes);
+    if (ret < 0) {
+        fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
+        res->check_errors++;
+        return ret;
+    }
+
+    for (i = 0; i < l1_size; i++) {
+        be64_to_cpus(&l1_table[i]);
     }
 
     /* Do the actual checks */
-    for(i = 0; i < l1_size; i++) {
-        l2_offset = l1_table[i];
-        if (l2_offset) {
-            /* Mark L2 table as used */
-            l2_offset &= L1E_OFFSET_MASK;
-            ret = qcow2_inc_refcounts_imrt(bs, res,
-                                           refcount_table, refcount_table_size,
-                                           l2_offset, s->cluster_size);
-            if (ret < 0) {
-                goto fail;
-            }
+    for (i = 0; i < l1_size; i++) {
+        if (!l1_table[i]) {
+            continue;
+        }
 
-            /* L2 tables are cluster aligned */
-            if (offset_into_cluster(s, l2_offset)) {
-                fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "
-                    "cluster aligned; L1 entry corrupted\n", l2_offset);
-                res->corruptions++;
-            }
+        l2_offset = l1_table[i] & L1E_OFFSET_MASK;
 
-            /* Process and check L2 entries */
-            ret = check_refcounts_l2(bs, res, refcount_table,
-                                     refcount_table_size, l2_offset, flags,
-                                     fix, active);
-            if (ret < 0) {
-                goto fail;
-            }
+        /* Mark L2 table as used */
+        ret = qcow2_inc_refcounts_imrt(bs, res,
+                                       refcount_table, refcount_table_size,
+                                       l2_offset, s->cluster_size);
+        if (ret < 0) {
+            return ret;
+        }
+
+        /* L2 tables are cluster aligned */
+        if (offset_into_cluster(s, l2_offset)) {
+            fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "
+                "cluster aligned; L1 entry corrupted\n", l2_offset);
+            res->corruptions++;
+        }
+
+        /* Process and check L2 entries */
+        ret = check_refcounts_l2(bs, res, refcount_table,
+                                 refcount_table_size, l2_offset, flags,
+                                 fix, active);
+        if (ret < 0) {
+            return ret;
         }
     }
-    g_free(l1_table);
-    return 0;
 
-fail:
-    g_free(l1_table);
-    return ret;
+    return 0;
 }
 
 /*
-- 
2.29.2

[PATCH v4 09/10] qcow2-refcount: check_refcounts_l1(): check reserved bits

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2.h          | 1 +
 block/qcow2-refcount.c | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/block/qcow2.h b/block/qcow2.h
index b8b1093b61..58fd7f1678 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -586,6 +586,7 @@ typedef enum QCow2MetadataOverlap {
     (QCOW2_OL_CACHED | QCOW2_OL_INACTIVE_L2)
 
 #define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
+#define L1E_RESERVED_MASK 0x7f000000000001ffULL
 #define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
 #define L2E_STD_RESERVED_MASK 0x3f000000000001feULL
 
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 153e5ca087..75751a0181 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1900,6 +1900,12 @@ static int check_refcounts_l1(BlockDriverState *bs,
             continue;
         }
 
+        if (l1_table[i] & L1E_RESERVED_MASK) {
+            fprintf(stderr, "ERROR found L1 entry with reserved bits set: "
+                    "%" PRIx64 "\n", l1_table[i]);
+            res->corruptions++;
+        }
+
         l2_offset = l1_table[i] & L1E_OFFSET_MASK;
 
         /* Mark L2 table as used */
-- 
2.29.2

[PATCH v4 10/10] qcow2-refcount: check_refblocks(): add separate message for reserved

[Vladimir Sementsov-Ogievskiy]

Split checking for reserved bits out of aligned offset check.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2.h          |  1 +
 block/qcow2-refcount.c | 10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 58fd7f1678..fd48a89d45 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -591,6 +591,7 @@ typedef enum QCow2MetadataOverlap {
 #define L2E_STD_RESERVED_MASK 0x3f000000000001feULL
 
 #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
+#define REFT_RESERVED_MASK 0x1ffULL
 
 #define INV_OFFSET (-1ULL)
 
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 75751a0181..d70667916b 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -2087,9 +2087,17 @@ static int check_refblocks(BlockDriverState *bs, BdrvCheckResult *res,
 
     for(i = 0; i < s->refcount_table_size; i++) {
         uint64_t offset, cluster;
-        offset = s->refcount_table[i];
+        offset = s->refcount_table[i] & REFT_OFFSET_MASK;
         cluster = offset >> s->cluster_bits;
 
+        if (s->refcount_table[i] & REFT_RESERVED_MASK) {
+            fprintf(stderr, "ERROR refcount table entry %" PRId64 " has "
+                    "reserved bits set\n", i);
+            res->corruptions++;
+            *rebuild = true;
+            continue;
+        }
+
         /* Refcount blocks are cluster aligned */
         if (offset_into_cluster(s, offset)) {
             fprintf(stderr, "ERROR refcount block %" PRId64 " is not "
-- 
2.29.2

Re: [PATCH v4 00/10] qcow2 check: check some reserved bits and subcluster bitmaps

[Hanna Reitz]

On 14.09.21 14:24, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
>
> Here are some good refactorings and new (qemu-img check) checks for
> qcow2.

Thanks, applied to my block branch:

https://gitlab.com/hreitz/qemu/-/commits/block/

(Patch 6 is here: 
https://gitlab.com/hreitz/qemu/-/commit/93c40e7dab205047245028e97f7470d89c3a7ef3 
– just to confirm the resolution fits what you had in mind)

Hanna

Re: [PATCH v4 00/10] qcow2 check: check some reserved bits and subcluster bitmaps

[Vladimir Sementsov-Ogievskiy]

15.09.2021 13:26, Hanna Reitz wrote:
> On 14.09.21 14:24, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Here are some good refactorings and new (qemu-img check) checks for
>> qcow2.
> 
> Thanks, applied to my block branch:
> 
> https://gitlab.com/hreitz/qemu/-/commits/block/
> 
> (Patch 6 is here: https://gitlab.com/hreitz/qemu/-/commit/93c40e7dab205047245028e97f7470d89c3a7ef3 – just to confirm the resolution fits what you had in mind)
> 

It's OK, thanks!


-- 
Best regards,
Vladimir