From 958a04bd32af18d9a207bcc78046e56a202aebc2 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 30 Apr 2020 16:27:54 +0200 Subject: [PATCH] backup: Make sure that source and target size match Since the introduction of a backup filter node in commit 00e30f05d, the backup block job crashes when the target image is smaller than the source image because it will try to write after the end of the target node without having BLK_PERM_RESIZE. (Previously, the BlockBackend layer would have caught this and errored out gracefully.) We can fix this and even do better than the old behaviour: Check that source and target have the same image size at the start of the block job and unshare BLK_PERM_RESIZE. (This permission was already unshared before the same commit 00e30f05d, but the BlockBackend that was used to make the restriction was removed without a replacement.) This will immediately error out when starting the job instead of only when writing to a block that doesn't exist in the target. Longer target than source would technically work because we would never write to blocks that don't exist, but semantically these are invalid, too, because a backup is supposed to create a copy, not just an image that starts with a copy. Fixes: 00e30f05de1d19586345ec373970ef4c192c6270 Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1778593 Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Message-Id: <20200430142755.315494-4-kwolf@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy Signed-off-by: Kevin Wolf --- block/backup-top.c | 14 +++++++++----- block/backup.c | 14 +++++++++++++- 2 files changed, 22 insertions(+), 6 deletions(-) diff --git a/block/backup-top.c b/block/backup-top.c index 3b50c06e2c..79b268e6dc 100644 --- a/block/backup-top.c +++ b/block/backup-top.c @@ -148,8 +148,10 @@ static void backup_top_child_perm(BlockDriverState *bs, BdrvChild *c, * * Share write to target (child_file), to not interfere * with guest writes to its disk which may be in target backing chain. + * Can't resize during a backup block job because we check the size + * only upfront. */ - *nshared = BLK_PERM_ALL; + *nshared = BLK_PERM_ALL & ~BLK_PERM_RESIZE; *nperm = BLK_PERM_WRITE; } else { /* Source child */ @@ -159,7 +161,7 @@ static void backup_top_child_perm(BlockDriverState *bs, BdrvChild *c, if (perm & BLK_PERM_WRITE) { *nperm = *nperm | BLK_PERM_CONSISTENT_READ; } - *nshared &= ~BLK_PERM_WRITE; + *nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); } } @@ -192,11 +194,13 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source, { Error *local_err = NULL; BDRVBackupTopState *state; - BlockDriverState *top = bdrv_new_open_driver(&bdrv_backup_top_filter, - filter_node_name, - BDRV_O_RDWR, errp); + BlockDriverState *top; bool appended = false; + assert(source->total_sectors == target->total_sectors); + + top = bdrv_new_open_driver(&bdrv_backup_top_filter, filter_node_name, + BDRV_O_RDWR, errp); if (!top) { return NULL; } diff --git a/block/backup.c b/block/backup.c index c4c3b8cd46..4f13bb20a5 100644 --- a/block/backup.c +++ b/block/backup.c @@ -340,7 +340,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, BlockCompletionFunc *cb, void *opaque, JobTxn *txn, Error **errp) { - int64_t len; + int64_t len, target_len; BackupBlockJob *job = NULL; int64_t cluster_size; BdrvRequestFlags write_flags; @@ -405,6 +405,18 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, goto error; } + target_len = bdrv_getlength(target); + if (target_len < 0) { + error_setg_errno(errp, -target_len, "Unable to get length for '%s'", + bdrv_get_device_or_node_name(bs)); + goto error; + } + + if (target_len != len) { + error_setg(errp, "Source and target image have different sizes"); + goto error; + } + cluster_size = backup_calculate_cluster_size(target, errp); if (cluster_size < 0) { goto error; -- 2.11.4.GIT