OpenE2K/qemu-e2k
13
4
Fork 0
Code Issues 4 Pull Requests Projects 2 Releases Activity

qemu-io: Allow larger write zeroes under no fallback

Browse Source 
When writing zeroes can fall back to a slow write, permitting an
overly large request can become an amplification denial of service
attack in triggering a large amount of work from a small request.  But
the whole point of the no fallback flag is to quickly determine if
writing an entire device to zero can be done quickly (such as when it
is already known that the device started with zero contents); in those
cases, artificially capping things at 2G in qemu-io itself doesn't
help us.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20211203231539.3900865-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
This commit is contained in:
Eric Blake 2021-12-03 17:15:28 -06:00
parent 087f2fb376
commit 395aecd037
1 changed files with 3 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
qemu-io-cmds.c
View File

@ -603,10 +603,6 @@ static int do_co_pwrite_zeroes(BlockBackend *blk, int64_t offset,
.done = false, .done = false,
}; };
if (bytes > INT_MAX) {
return -ERANGE;
}
co = qemu_coroutine_create(co_pwrite_zeroes_entry, &data); co = qemu_coroutine_create(co_pwrite_zeroes_entry, &data);
bdrv_coroutine_enter(blk_bs(blk), co); bdrv_coroutine_enter(blk_bs(blk), co);
while (!data.done) { while (!data.done) {
@ -1160,8 +1156,9 @@ static int write_f(BlockBackend *blk, int argc, char **argv)
if (count < 0) { if (count < 0) {
print_cvtnum_err(count, argv[optind]); print_cvtnum_err(count, argv[optind]);
return count; return count;
} else if (count > BDRV_REQUEST_MAX_BYTES) { } else if (count > BDRV_REQUEST_MAX_BYTES &&
printf("length cannot exceed %" PRIu64 ", given %s\n", !(flags & BDRV_REQ_NO_FALLBACK)) {
printf("length cannot exceed %" PRIu64 " without -n, given %s\n",
(uint64_t)BDRV_REQUEST_MAX_BYTES, argv[optind]); (uint64_t)BDRV_REQUEST_MAX_BYTES, argv[optind]);
return -EINVAL; return -EINVAL;
} }