On 5/6/26 09:51, Rob Herring wrote:
On Wed, Apr 29, 2026 at 02:58:22PM +0800, Chen Wandun wrote:
early_init_dt_reserve_memory() does not validate whether the region
falls within physical memory. If a device tree incorrectly specifies a
reserved memory region outside the physical address range:
- For the non-nomap path, memblock_reserve() blindly adds the region
to memblock.reserved, creating a stale entry that refers to
non-existent memory.
- For the nomap path, memblock_mark_nomap() silently fails to match
any region in memblock.memory, but still returns success.
Add a memblock_overlaps_region() check at the entry of
early_init_dt_reserve_memory() to reject such regions before any
memblock operation takes place. This also simplifies the existing nomap
guard: the original "overlaps && is_reserved" condition reduces to just
"is_reserved", since the overlap with physical memory is already
guaranteed by the new check.
While I agree, I suspect we already have cases abusing reserved-memory
like this.
Sashiko reviewed this patch and told me:
"Historically, the reserved-memory binding is often used to describe
hardware
SRAM, DSP memory, or IOMEM carveouts that reside outside of system RAM."
IIUC, nowdays using mmio-sram DT binding is more appropriate for SRAM or
IOMEM carveouts.
Should I drop this patch or keep it ?
Thanks.
Signed-off-by: Chen Wandun <[email protected]>
Tested-by: Zhao Meijing <[email protected]>
---
drivers/of/of_reserved_mem.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 9d1b0193864c..03c676052dab 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -112,14 +112,21 @@ static int fdt_fixup_reserved_mem_node(unsigned long node,
static int __init early_init_dt_reserve_memory(phys_addr_t base,
phys_addr_t size, bool nomap)
{
+ if (!memblock_overlaps_region(&memblock.memory, base, size)) {
+ phys_addr_t end = base + size - 1;
+
+ pr_warn("Reserved memory region %pa..%pa is outside of physical
memory\n",
+ &base, &end);
+ return -EINVAL;
+ }
+
if (nomap) {
/*
* If the memory is already reserved (by another region), we
- * should not allow it to be marked nomap, but don't worry
- * if the region isn't memory as it won't be mapped.
+ * should not allow it to be marked nomap. The region being
+ * physical memory is guaranteed by the overlap check above.
*/
- if (memblock_overlaps_region(&memblock.memory, base, size) &&
- memblock_is_region_reserved(base, size))
+ if (memblock_is_region_reserved(base, size))
return -EBUSY;
return memblock_mark_nomap(base, size);
--
2.43.0
