[PATCH v2 wireless-next] wifi: ath12k: Fix out-of-bounds read in ath12k_mac_vdev_create

[Dheeraj Reddy Jonnalagadda <dheeraj.linuxdev@gmail.com>]

Add a bounds check to ath12k_mac_vdev_create() to prevent an out-of-bounds
read in the vif->link_conf array. The function uses link_id, derived from
arvif->link_id, to index the array. When link_id equals 15, the index
exceeds the bounds of the array, which contains only 15 elements.

This issue occurs in the following code branch:

    if (arvif->link_id == ATH12K_DEFAULT_SCAN_LINK && vif->valid_links)
        link_id = ffs(vif->valid_links) - 1;
    else
        link_id = arvif->link_id;

When the first condition in the if statement is true and the second
condition is false, it implies that arvif->link_id equals 15 and
the else branch is taken, where link_id is set to 15, causing an
out-of-bounds access when vif->link_conf array is read using link_id
as index.

Add a check to ensure that link_id does not exceed the valid range of the
vif->link_conf array. Log a warning and return -EINVAL if the check fails
to prevent undefined behavior.

Changelog:

v2:
	- Updated the commit message as per the reviewer's suggestions
	- Clarified the description of the bug in the commit message
	- Added Fixes and Closes tags with relevant information

Fixes: 90570ba4610 ("wifi: ath12k: do not return invalid link id for scan link")
Closes: https://scan7.scan.coverity.com/#/project-view/52337/11354?selectedIssue=1602214

Signed-off-by: Dheeraj Reddy Jonnalagadda <dheeraj.linuxdev@gmail.com>
---
 drivers/net/wireless/ath/ath12k/mac.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
index 129607ac6c1a..c19b10e66f4a 100644
--- a/drivers/net/wireless/ath/ath12k/mac.c
+++ b/drivers/net/wireless/ath/ath12k/mac.c
@@ -7725,6 +7725,12 @@ int ath12k_mac_vdev_create(struct ath12k *ar, struct ath12k_link_vif *arvif)
 	else
 		link_id = arvif->link_id;
 
+	if (link_id >= ARRAY_SIZE(vif->link_conf)) {
+		ath12k_warn(ar->ab, "link_id %u exceeds max valid links for vif %pM\n",
+			    link_id, vif->addr);
+		return -EINVAL;
+	}
+
 	link_conf = wiphy_dereference(hw->wiphy, vif->link_conf[link_id]);
 	if (!link_conf) {
 		ath12k_warn(ar->ab, "unable to access bss link conf in vdev create for vif %pM link %u\n",
-- 
2.34.1