[PATCH v2 1/2] of: reserved_mem: prevent OOB when too many dynamic regions are defined

[Sang-Heon Jeon <ekffu200098@gmail.com>]

On boot, fdt_scan_reserved_mem() saves each dynamically-placed
/reserved-memory subnode into a local array of size
MAX_RESERVED_REGIONS.

If the device tree defines more than MAX_RESERVED_REGIONS
dynamically-placed regions, fdt_scan_reserved_mem() writes past the
end of the local array.

Add a bounds check that logs an error and skips the excess regions,
restoring the original behavior.

Fixes: 8a6e02d0c00e ("of: reserved_mem: Restructure how the reserved memory regions are processed")
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
 drivers/of/of_reserved_mem.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 82222bd45ac6..42e3e2d8a2b8 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -359,6 +359,7 @@ int __init fdt_scan_reserved_mem(void)
 		err = __reserved_mem_reserve_reg(child, uname);
 		if (!err)
 			count++;
+
 		/*
 		 * Save the nodes for the dynamically-placed regions
 		 * into an array which will be used for allocation right
@@ -366,10 +367,17 @@ int __init fdt_scan_reserved_mem(void)
 		 * or marked as no-map. This is done to avoid dynamically
 		 * allocating from one of the statically-placed regions.
 		 */
-		if (err == -ENOENT && of_get_flat_dt_prop(child, "size", NULL)) {
-			dynamic_nodes[dynamic_nodes_cnt] = child;
-			dynamic_nodes_cnt++;
+		if (err != -ENOENT || !of_get_flat_dt_prop(child, "size", NULL))
+			continue;
+
+		if (dynamic_nodes_cnt == MAX_RESERVED_REGIONS) {
+			pr_err("too many defined dynamic regions, skip '%s'\n",
+			       uname);
+			continue;
 		}
+
+		dynamic_nodes[dynamic_nodes_cnt] = child;
+		dynamic_nodes_cnt++;
 	}
 	for (int i = 0; i < dynamic_nodes_cnt; i++) {
 		const char *uname;
-- 
2.43.0