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authorStefan Hajnoczi <stefanha@redhat.com>2021-07-26 13:28:39 +0100
committerHanna Reitz <hreitz@redhat.com>2021-09-01 12:57:31 +0200
commitb68ce824098e4470e5c4f81065896a9ca8a45792 (patch)
tree19a61ef55665bb0d02d94b119bd627d788fe0643 /block
parent8cca0bd289ed8aa1f4f26539bd9450fa04e16fc0 (diff)
raw-format: drop WRITE and RESIZE child perms when possible
The following command-line fails due to a permissions conflict: $ qemu-storage-daemon \ --blockdev driver=nvme,node-name=nvme0,device=0000:08:00.0,namespace=1 \ --blockdev driver=raw,node-name=l1-1,file=nvme0,offset=0,size=1073741824 \ --blockdev driver=raw,node-name=l1-2,file=nvme0,offset=1073741824,size=1073741824 \ --nbd-server addr.type=unix,addr.path=/tmp/nbd.sock,max-connections=2 \ --export type=nbd,id=nbd-l1-1,node-name=l1-1,name=l1-1,writable=on \ --export type=nbd,id=nbd-l1-2,node-name=l1-2,name=l1-2,writable=on qemu-storage-daemon: --export type=nbd,id=nbd-l1-1,node-name=l1-1,name=l1-1,writable=on: Permission conflict on node 'nvme0': permissions 'resize' are both required by node 'l1-1' (uses node 'nvme0' as 'file' child) and unshared by node 'l1-2' (uses node 'nvme0' as 'file' child). The problem is that block/raw-format.c relies on bdrv_default_perms() to set permissions on the nvme node. The default permissions add RESIZE in anticipation of a format driver like qcow2 that needs to grow the image file. This fails because RESIZE is unshared, so we cannot get the RESIZE permission. Max Reitz pointed out that block/crypto.c already handles this case by implementing a custom ->bdrv_child_perm() function that adjusts the result of bdrv_default_perms(). This patch takes the same approach in block/raw-format.c so that RESIZE is only required if it's actually necessary (e.g. the parent is qcow2). Cc: Max Reitz <mreitz@redhat.com> Cc: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20210726122839.822900-1-stefanha@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/raw-format.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/block/raw-format.c b/block/raw-format.c
index 7717578ed6..c26f493688 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -580,6 +580,25 @@ static void raw_cancel_in_flight(BlockDriverState *bs)
bdrv_cancel_in_flight(bs->file->bs);
}
+static void raw_child_perm(BlockDriverState *bs, BdrvChild *c,
+ BdrvChildRole role,
+ BlockReopenQueue *reopen_queue,
+ uint64_t parent_perm, uint64_t parent_shared,
+ uint64_t *nperm, uint64_t *nshared)
+{
+ bdrv_default_perms(bs, c, role, reopen_queue, parent_perm,
+ parent_shared, nperm, nshared);
+
+ /*
+ * bdrv_default_perms() may add WRITE and/or RESIZE (see comment in
+ * bdrv_default_perms_for_storage() for an explanation) but we only need
+ * them if they are in parent_perm. Drop WRITE and RESIZE whenever possible
+ * to avoid permission conflicts.
+ */
+ *nperm &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
+ *nperm |= parent_perm & (BLK_PERM_WRITE | BLK_PERM_RESIZE);
+}
+
BlockDriver bdrv_raw = {
.format_name = "raw",
.instance_size = sizeof(BDRVRawState),
@@ -588,7 +607,7 @@ BlockDriver bdrv_raw = {
.bdrv_reopen_commit = &raw_reopen_commit,
.bdrv_reopen_abort = &raw_reopen_abort,
.bdrv_open = &raw_open,
- .bdrv_child_perm = bdrv_default_perms,
+ .bdrv_child_perm = raw_child_perm,
.bdrv_co_create_opts = &raw_co_create_opts,
.bdrv_co_preadv = &raw_co_preadv,
.bdrv_co_pwritev = &raw_co_pwritev,