[Devel] [PATCH RHEL10 COMMIT] dm-qcow2: forbid unaligned virtual size for images

[Konstantin Khorenko]

The commit is pushed to "branch-rh10-6.12.0-211.39.1.16.x.vz10-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh10-6.12.0-211.39.1.16.9.vz10
------>
commit ad515b7f0e026dbec6cb947562e21f7f014543c7
Author: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
Date:   Wed Aug 19 03:07:45 2026 +0300

    dm-qcow2: forbid unaligned virtual size for images
    
    There are a few places where we do to_sector() conversions which
    may cause us bugs when the image size is not aligned. For example,
    advance_and_spawn_lower_seek_qio() advances old_qio to
    to_sector(end). If end is not aliged, it may round down to the
    same sector already set in old_qio. Thus we will endlessly loop.
    
    It is OK to forbid such images since QEMU rounds up virtual size
    on qcow2 creation and rejects unaligned resizes.
    
    https://virtuozzo.atlassian.net/browse/VSTOR-139407
    Feature: dm-qcow2: block device over QCOW2 files driver
    Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
    Reviewed-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
    Reviewed-by: Vasileios Almpanis <vasileios.almpanis at virtuozzo.com>
---
 drivers/md/dm-qcow2-target.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/dm-qcow2-target.c b/drivers/md/dm-qcow2-target.c
index de1fb628735b7..2877de6f11c12 100644
--- a/drivers/md/dm-qcow2-target.c
+++ b/drivers/md/dm-qcow2-target.c
@@ -541,6 +541,7 @@ static int qcow2_check_convert_hdr(struct dm_target *ti,
 
 	clu_size = 1 << hdr->cluster_bits;
 	if (hdr->size < min_len || hdr->size > max_len ||
+	    !IS_ALIGNED(hdr->size, SECTOR_SIZE) ||
 	    /* Note, we do not extend L1 table: */
 	    (u64)hdr->l1_size * clu_size / sizeof(u64) * clu_size < min_len)
 		return -EBADSLT;