[PATCH v2 1/4] ublk: check recovery flags for validity

[Uday Shankar <ushankar@purestorage.com>]

Setting UBLK_F_USER_RECOVERY_REISSUE without also setting
UBLK_F_USER_RECOVERY is currently silently equivalent to not setting any
recovery flags at all, even though that's obviously not intended. Check
for this case and fail add_dev (with a paranoid warning to aid debugging
any program which might rely on the old behavior) with EINVAL if it is
detected.

Signed-off-by: Uday Shankar <ushankar@purestorage.com>
---
Changes since v1 (https://lore.kernel.org/linux-block/20240617194451.435445-2-ushankar@purestorage.com/):
- Replace switch statement with if statement

 drivers/block/ublk_drv.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index bca06bfb4bc3..5e04a0fcd0b7 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -62,6 +62,9 @@
 		| UBLK_F_USER_COPY \
 		| UBLK_F_ZONED)
 
+#define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
+		| UBLK_F_USER_RECOVERY_REISSUE)
+
 /* All UBLK_PARAM_TYPE_* should be included here */
 #define UBLK_PARAM_TYPE_ALL                                \
 	(UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD | \
@@ -2373,6 +2376,14 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
 	else if (!(info.flags & UBLK_F_UNPRIVILEGED_DEV))
 		return -EPERM;
 
+	/* forbid nonsense combinations of recovery flags */
+	if ((info.flags & UBLK_F_USER_RECOVERY_REISSUE) &&
+	    !(info.flags & UBLK_F_USER_RECOVERY)) {
+		pr_warn("%s: invalid recovery flags %llx\n", __func__,
+			info.flags & UBLK_F_ALL_RECOVERY_FLAGS);
+		return -EINVAL;
+	}
+
 	/*
 	 * unprivileged device can't be trusted, but RECOVERY and
 	 * RECOVERY_REISSUE still may hang error handling, so can't
-- 
2.34.1