From: Doug Berger <opendmb@xxxxxxxxx> Subject: 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/1561422051-16142-1-git-send-email-opendmb@xxxxxxxxx Fixes: 5ea3b1b2f8ad ("cma: add placement specifier for "cma=" kernel parameter") Signed-off-by: Doug Berger <opendmb@xxxxxxxxx> Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx> Cc: Yue Hu <huyue2@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: Laura Abbott <labbott@xxxxxxxxxx> Cc: Peng Fan <peng.fan@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/cma.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- a/mm/cma.c~cma-fail-if-fixed-declaration-cant-be-honored +++ a/mm/cma.c @@ -278,6 +278,12 @@ int __init cma_declare_contiguous(phys_a */ 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_a 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) || _
