cma-enforce-non-zero-pageblock_order-during-cma_init_reserved_mem.patch removed from -mm tree

The quilt patch titled
Subject: cma: enforce non-zero pageblock_order during cma_init_reserved_mem()
has been removed from the -mm tree. Its filename was
cma-enforce-non-zero-pageblock_order-during-cma_init_reserved_mem.patch

This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "Ritesh Harjani (IBM)" <[email protected]>
Subject: cma: enforce non-zero pageblock_order during cma_init_reserved_mem()
Date: Wed, 13 Nov 2024 19:49:54 +0530

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/[email protected]/

---

 mm/cma.c |    9 +++++++++
 1 file changed, 9 insertions(+)

@@ -181,6 +181,15 @@ int __init cma_init_reserved_mem(phys_ad
 	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;

_

Patches currently in -mm which might be from [email protected] are