[PATCH v2 2/2] blk-zoned: allow BLKREPORTZONE without CAP_SYS_ADMIN

[Niklas Cassel]

From: Niklas Cassel <niklas.cassel@xxxxxxx>

Performing a BLKREPORTZONE operation should be allowed under the same
permissions as read(). (read() does not require CAP_SYS_ADMIN).

Remove the CAP_SYS_ADMIN requirement, and instead check that the fd was
successfully opened with FMODE_READ. This way BLKREPORTZONE will match
the access control requirement of read().

Fixes: 3ed05a987e0f ("blk-zoned: implement ioctls")
Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.10+
---
Changes since v1:
- Pick up tag from Damien.
- Add fixes tag and CC stable.

 block/blk-zoned.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 0789e6e9f7db..e05fe8dbb06d 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -288,8 +288,8 @@ int blkdev_report_zones_ioctl(struct block_device *bdev, fmode_t mode,
 	if (!blk_queue_is_zoned(q))
 		return -ENOTTY;
 
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
+	if (!(mode & FMODE_READ))
+		return -EBADF;
 
 	if (copy_from_user(&rep, argp, sizeof(struct blk_zone_report)))
 		return -EFAULT;
-- 
2.31.1