nbd/server: Hoist length check to qmp_nbd_server_add
We only had two callers to nbd_export_new; qemu-nbd.c always
passed a valid offset/length pair (because it already checked
the file length, to ensure that offset was in bounds), while
blockdev-nbd.c always passed 0/-1. Then nbd_export_new reduces
the size to a multiple of BDRV_SECTOR_SIZE (can only happen
when offset is not sector-aligned, since bdrv_getlength()
currently rounds up) (someday, it would be nice to have
byte-accurate lengths - but not today).
However, I'm finding it easier to work with the code if we are
consistent on having both callers pass in a valid length, and
just assert that things are sane in nbd_export_new, meaning
that no negative values were passed, and that offset+size does
not exceed 63 bits (as that really is a fundamental limit to
later operations, whether we use off_t or uint64_t).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190117193658.16413-6-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index c76d541..d73ac1b 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -146,6 +146,7 @@
BlockDriverState *bs = NULL;
BlockBackend *on_eject_blk;
NBDExport *exp;
+ int64_t len;
if (!nbd_server) {
error_setg(errp, "NBD server not running");
@@ -168,6 +169,13 @@
return;
}
+ len = bdrv_getlength(bs);
+ if (len < 0) {
+ error_setg_errno(errp, -len,
+ "Failed to determine the NBD export's length");
+ return;
+ }
+
if (!has_writable) {
writable = false;
}
@@ -175,7 +183,7 @@
writable = false;
}
- exp = nbd_export_new(bs, 0, -1, name, NULL, bitmap,
+ exp = nbd_export_new(bs, 0, len, name, NULL, bitmap,
writable ? 0 : NBD_FLAG_READ_ONLY,
NULL, false, on_eject_blk, errp);
if (!exp) {
diff --git a/nbd/server.c b/nbd/server.c
index 6b13601..51ee809 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1495,17 +1495,13 @@
exp->refcount = 1;
QTAILQ_INIT(&exp->clients);
exp->blk = blk;
+ assert(dev_offset >= 0 && dev_offset <= INT64_MAX);
exp->dev_offset = dev_offset;
exp->name = g_strdup(name);
exp->description = g_strdup(description);
exp->nbdflags = nbdflags;
- exp->size = size < 0 ? blk_getlength(blk) : size;
- if (exp->size < 0) {
- error_setg_errno(errp, -exp->size,
- "Failed to determine the NBD export's length");
- goto fail;
- }
- exp->size -= exp->size % BDRV_SECTOR_SIZE;
+ assert(size >= 0 && size <= INT64_MAX - dev_offset);
+ exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE);
if (bitmap) {
BdrvDirtyBitmap *bm = NULL;