qcow2: Add bounds check to get_refblock_offset()

Reported-by: R. Nageswara Sastry <nasastry@in.ibm.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1728661
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20171110203111.7666-5-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

2 files changed, 68 insertions, 0 deletions

diff --git a/tests/qemu-iotests/060 b/tests/qemu-iotests/060
index 44141f6..c230696 100755
--- a/tests/qemu-iotests/060
+++ b/tests/qemu-iotests/060
@@ -359,6 +359,52 @@ echo '--- Repairing ---'
 _check_test_img -q -r all
 _check_test_img -r all
 
+echo
+echo "=== Discarding an out-of-bounds refblock ==="
+echo
+
+_make_test_img 64M
+
+# Pretend there's a refblock really up high
+poke_file "$TEST_IMG" "$(($rt_offset+8))" "\x00\xff\xff\xff\x00\x00\x00\x00"
+# Let's try to shrink the qcow2 image so that the block driver tries
+# to discard that refblock (and see what happens!)
+$QEMU_IMG resize --shrink "$TEST_IMG" 32M
+
+echo '--- Checking and retrying ---'
+# Image should not be resized
+_img_info | grep 'virtual size'
+# But it should pass this check, because the "partial" resize has
+# already overwritten refblocks past the end
+_check_test_img -r all
+# So let's try again
+$QEMU_IMG resize --shrink "$TEST_IMG" 32M
+_img_info | grep 'virtual size'
+
+echo
+echo "=== Discarding a non-covered in-bounds refblock ==="
+echo
+
+IMGOPTS='refcount_bits=1' _make_test_img 64M
+
+# Pretend there's a refblock somewhere where there is no refblock to
+# cover it (but the covering refblock has a valid index in the
+# reftable)
+# Every refblock covers 65536 * 8 * 65536 = 32 GB, so we have to point
+# to 0x10_0000_0000 (64G) to point to the third refblock
+poke_file "$TEST_IMG" "$(($rt_offset+8))" "\x00\x00\x00\x10\x00\x00\x00\x00"
+$QEMU_IMG resize --shrink "$TEST_IMG" 32M
+
+echo '--- Checking and retrying ---'
+# Image should not be resized
+_img_info | grep 'virtual size'
+# But it should pass this check, because the "partial" resize has
+# already overwritten refblocks past the end
+_check_test_img -r all
+# So let's try again
+$QEMU_IMG resize --shrink "$TEST_IMG" 32M
+_img_info | grep 'virtual size'
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
diff --git a/tests/qemu-iotests/060.out b/tests/qemu-iotests/060.out
index 07dfdca..358e54c 100644
--- a/tests/qemu-iotests/060.out
+++ b/tests/qemu-iotests/060.out
@@ -348,4 +348,26 @@ The following inconsistencies were found and repaired:
 
 Double checking the fixed image now...
 No errors were found on the image.
+
+=== Discarding an out-of-bounds refblock ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+qcow2: Marking image as corrupt: Refblock at 0xffffff00000000 is not covered by the refcount structures; further corruption events will be suppressed
+qemu-img: Failed to discard unused refblocks: Input/output error
+--- Checking and retrying ---
+virtual size: 64M (67108864 bytes)
+No errors were found on the image.
+Image resized.
+virtual size: 32M (33554432 bytes)
+
+=== Discarding a non-covered in-bounds refblock ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+qcow2: Marking image as corrupt: Refblock at 0x1000000000 is not covered by the refcount structures; further corruption events will be suppressed
+qemu-img: Failed to discard unused refblocks: Input/output error
+--- Checking and retrying ---
+virtual size: 64M (67108864 bytes)
+No errors were found on the image.
+Image resized.
+virtual size: 32M (33554432 bytes)
 *** done