loop: loop_set_status_from_info() check before assignment

stable inclusion
from stable-v5.10.173
commit c79a924ed6afac1708dfd370ba66bcf6a852ced6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7JHOA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c79a924ed6afac1708dfd370ba66bcf6a852ced6

--------------------------------

[ Upstream commit 9f6ad5d5 ]

In loop_set_status_from_info(), lo->lo_offset and lo->lo_sizelimit should
be checked before reassignment, because if an overflow error occurs, the
original correct value will be changed to the wrong value, and it will not
be changed back.

More, the original patch did not solve the problem, the value was set and
ioctl returned an error, but the subsequent io used the value in the loop
driver, which still caused an alarm:

loop_handle_cmd
 do_req_filebacked
  loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
  lo_rw_aio
   cmd->iocb.ki_pos = pos

Fixes: c490a0b5 ("loop: Check for overflow while configuring loop")
Signed-off-by: NZhong Jinghua <zhongjinghua@huawei.com>
Reviewed-by: NChaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20230221095027.3656193-1-zhongjinghua@huaweicloud.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZhong Jinghua <zhongjinghua@huawei.com>
(cherry picked from commit cfb3aa6f)

drivers/block/loop.c

@@ -1029,13 +1029,13 @@ loop_set_status_from_info(struct loop_device *lo,
 	if (err)
 		return err;
 
+	/* Avoid assigning overflow values */
+	if (info->lo_offset > LLONG_MAX || info->lo_sizelimit > LLONG_MAX)
+		return -EOVERFLOW;
+
 	lo->lo_offset = info->lo_offset;
 	lo->lo_sizelimit = info->lo_sizelimit;
 
-	/* loff_t vars have been assigned __u64 */
-	if (lo->lo_offset < 0 || lo->lo_sizelimit < 0)
-		return -EOVERFLOW;
-
 	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
 	memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
 	lo->lo_file_name[LO_NAME_SIZE-1] = 0;