mm/cma.c: fail if fixed declaration can't be honored

The description of cma_declare_contiguous() indicates that if the
'fixed' argument is true the reserved contiguous area must be exactly at
the address of the 'base' argument.

However, the function currently allows the 'base', 'size', and 'limit'
arguments to be silently adjusted to meet alignment constraints.  This
commit enforces the documented behavior through explicit checks that
return an error if the region does not fit within a specified region.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 5ea3b1b2f8ad ("cma: add placement specifier for "cma=" kernel parameter")
Signed-off-by: Doug Berger <[email protected]>
Acked-by: Michal Nazarewicz <[email protected]>
Cc: Yue Hu <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Peng Fan <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 13 insertions, 0 deletions

diff --git a/mm/cma.c b/mm/cma.c
index d415dfc0965e..7fe0b8356775 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -278,6 +278,12 @@ int __init cma_declare_contiguous(phys_addr_t base,
 	 */
 	alignment = max(alignment,  (phys_addr_t)PAGE_SIZE <<
 			  max_t(unsigned long, MAX_ORDER - 1, pageblock_order));
+	if (fixed && base & (alignment - 1)) {
+		ret = -EINVAL;
+		pr_err("Region at %pa must be aligned to %pa bytes\n",
+			&base, &alignment);
+		goto err;
+	}
 	base = ALIGN(base, alignment);
 	size = ALIGN(size, alignment);
 	limit &= ~(alignment - 1);
@@ -308,6 +314,13 @@ int __init cma_declare_contiguous(phys_addr_t base,
 	if (limit == 0 || limit > memblock_end)
 		limit = memblock_end;
 
+	if (base + size > limit) {
+		ret = -EINVAL;
+		pr_err("Size (%pa) of region at %pa exceeds limit (%pa)\n",
+			&size, &base, &limit);
+		goto err;
+	}
+
 	/* Reserve memory */
 	if (fixed) {
 		if (memblock_is_region_reserved(base, size) ||