[PATCH v2 3/5] of: reserved_mem: reject statically placed regions overlapping existing reservations

[Wandun Chen <chenwandun1@gmail.com>]

From: Wandun Chen <chenwandun@lixiang.com>

memblock_reserve() permits overlapping reservations, so a statically
placed region whose 'reg' overlaps an existing one is accepted. When
initialization of a statically placed reserved-memory region
overlapping an existing reservation fails, memblock_phys_free()
returns the overlap to the buddy allocator, corrupting that memory.

Reject the overlap up front. Dynamically allocated regions are
unaffected, as they are allocated from free memory and so cannot
overlap an existing reservation.

Sashiko found this issue in [1].

Fixes: d0b8ed47e83a ("of: reserved_mem: fix reserve memory leak")
Signed-off-by: Wandun Chen <chenwandun@lixiang.com>
Link: https://sashiko.dev/#/message/20260806100605.2C2C01F000E9%40smtp.kernel.org [1]
---
 drivers/of/of_reserved_mem.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 9fb2e4c29443..767ef702392e 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -158,6 +158,11 @@ static int __init early_init_dt_reserve_memory(phys_addr_t base,
 
 		return memblock_mark_nomap(base, size);
 	}
+
+	if (memblock_is_region_reserved(base, size) ||
+	    memblock_overlaps_nomap(base, size))
+		return -EBUSY;
+
 	return memblock_reserve(base, size);
 }
 
-- 
2.43.0