Patch "loop: loop_set_status_from_info() check before assignment" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    loop: loop_set_status_from_info() check before assignment

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     loop-loop_set_status_from_info-check-before-assignme.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit ae8f0e0e5ec6983e634a8af4a64c0f62a0c162c0
Author: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
Date:   Tue Feb 21 17:50:27 2023 +0800

    loop: loop_set_status_from_info() check before assignment
    
    [ 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@xxxxxxxxxx>
    Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230221095027.3656193-1-zhongjinghua@xxxxxxxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 68a0c0fe64dd8..58a38e61de535 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1152,13 +1152,13 @@ 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;