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[linux-5.4.y,8/8] loop: loop_set_status_from_info() check before assignment

Message ID 20240307041411.3792061-9-zhanggenjian@126.com (mailing list archive)
State New, archived
Headers show
Series Fix the UAF issue caused by the loop driver | expand

Commit Message

Genjian March 7, 2024, 4:14 a.m. UTC 
From: Zhong Jinghua <zhongjinghua@huawei.com>

[ Upstream commit 9f6ad5d533d1c71e51bdd06a5712c4fbc8768dfa ]

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: c490a0b5a4f3 ("loop: Check for overflow while configuring loop")
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20230221095027.3656193-1-zhongjinghua@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Genjian Zhang <zhanggenjian@kylinos.cn>
---
 drivers/block/loop.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
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Patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c999eef4e345..ff452c02b61f 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1296,13 +1296,13 @@  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;