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. Acked-by: David Hildenbrand <da...@redhat.com> Acked-by: Zi Yan <z...@nvidia.com> Reviewed-by: Anshuman Khandual <anshuman.khand...@arm.com> Signed-off-by: Ritesh Harjani (IBM) <ritesh.l...@gmail.com> --- RFCv3 -> v4: 1. Dropped RFC tagged as requested by Andrew. 2. Updated the changelog & added background as requested by Andrew [RFCv3] 3. Added acked-by and RBs tags. 4. Small commit msg update. 5. No functional changes. [RFCv3]: https://lore.kernel.org/all/20241112225902.f20215e5015f4d7cdf502...@linux-foundation.org/ Background - ============ 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.l...@gmail.com/ [2]: https://lore.kernel.org/all/83eb128e-4f06-4725-a843-a4563f246...@redhat.com/ mm/cma.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/cma.c b/mm/cma.c index 3e9724716bad..36d753e7a0bf 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -182,6 +182,15 @@ 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; -- 2.46.0
