[PATCH 2/4] nvme: reject invalid pr_read_keys() num_keys values

[Stefan Hajnoczi <stefanha@redhat.com>]

The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
Reservation Report command has a u32 maximum length. Reject num_keys
values that are too large to fit.

This will become important when pr_read_keys() is exposed to untrusted
userspace via an <linux/pr.h> ioctl.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 drivers/nvme/host/pr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
index ca6a74607b139..476a0518a11ca 100644
--- a/drivers/nvme/host/pr.c
+++ b/drivers/nvme/host/pr.c
@@ -233,6 +233,11 @@ static int nvme_pr_read_keys(struct block_device *bdev,
 	int ret, i;
 	bool eds;
 
+	/* Check that keys fit into u32 rse_len */
+	if (num_keys > -(u32)offsetof(typeof(*rse), regctl_eds) /
+	               sizeof(rse->regctl_eds[0]))
+		return -EINVAL;
+
 	/*
 	 * Assume we are using 128-bit host IDs and allocate a buffer large
 	 * enough to get enough keys to fill the return keys buffer.
-- 
2.52.0