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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>
master
Eric Blake 2019-01-17 13:36:42 -06:00
parent 4485936b6d
commit 7596bbb390
2 changed files with 12 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
blockdev-nbd.c
View File

@ -146,6 +146,7 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
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 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
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 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
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) {

10
nbd/server.c
View File

@ -1495,17 +1495,13 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
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;