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

[ Upstream commit c633324e311243586675e732249339685e5d6faa ]

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@gmail.com
Fixes: 5ea3b1b2f8ad ("cma: add placement specifier for "cma=" kernel parameter")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Yue Hu <huyue2@yulong.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/mm/cma.c b/mm/cma.c
index 4ea0f32761c1a00753e365cdf5d8cd5290a9e436..7cb569a188c488c7780e4b650f25c2fd00d769c7 100644 (file)
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -268,6 +268,12 @@ 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);
@@ -298,6 +304,13 @@ 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) ||