From 2532e6c74a67e65b95f310946e0c0e0a41b3a34b Mon Sep 17 00:00:00 2001 From: "Ritesh Harjani (IBM)" Date: Wed, 13 Nov 2024 19:49:54 +0530 Subject: cma: enforce non-zero pageblock_order during cma_init_reserved_mem() cma_init_reserved_mem() checks base and size alignment with CMA_MIN_ALIGNMENT_BYTES. However, some users might call this during early boot when pageblock_order is 0. That means if base and size does not have pageblock_order alignment, it can cause functional failures during cma activate area. So let's enforce pageblock_order to be non-zero during cma_init_reserved_mem() to catch such wrong usages. 1. This was seen with fadump on PowerPC which was calling cma_init_reserved_mem() before the pageblock_order was initialized. This is now fixed in the fadump on PowerPC itself. The details of that can be found in the patch including the userspace-visible effect of the issue [1]. 2. However it was also decided that we should add a stronger enforcement check within cma_init_reserved_mem() to catch such wrong usages [2]. Hence this patch. This is ok to be in -next and there is no "Fixes" tag required for this patch. [1]: https://lore.kernel.org/all/3ae208e48c0d9cefe53d2dc4f593388067405b7d.1729146153.git.ritesh.list@gmail.com/ [2]: https://lore.kernel.org/all/83eb128e-4f06-4725-a843-a4563f246a44@redhat.com/ Link: https://lkml.kernel.org/r/e274344b44d5f80fa54c52f530387257fe99ec65.1731505681.git.ritesh.list@gmail.com Signed-off-by: Ritesh Harjani (IBM) Acked-by: David Hildenbrand Acked-by: Zi Yan Reviewed-by: Anshuman Khandual Signed-off-by: Andrew Morton --- mm/cma.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'mm') diff --git a/mm/cma.c b/mm/cma.c index c5869d0001ad..de5bc0c81fc2 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -181,6 +181,15 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size, if (!size || !memblock_is_region_reserved(base, size)) return -EINVAL; + /* + * CMA uses CMA_MIN_ALIGNMENT_BYTES as alignment requirement which + * needs pageblock_order to be initialized. Let's enforce it. + */ + if (!pageblock_order) { + pr_err("pageblock_order not yet initialized. Called during early boot?\n"); + return -EINVAL; + } + /* ensure minimal alignment required by mm core */ if (!IS_ALIGNED(base | size, CMA_MIN_ALIGNMENT_BYTES)) return -EINVAL; -- cgit v1.2.3-70-g09d2