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. > > 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 >
