The patch titled
Subject: cma: enforce non-zero pageblock_order during cma_init_reserved_mem()
has been added to the -mm mm-unstable branch. Its filename is
cma-enforce-non-zero-pageblock_order-during-cma_init_reserved_mem.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/cma-enforce-non-zero-pageblock_order-during-cma_init_reserved_mem.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Ritesh Harjani (IBM)" <ritesh.list@xxxxxxxxx>
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@xxxxxxxxx/
[2]: https://lore.kernel.org/all/83eb128e-4f06-4725-a843-a4563f246a44@xxxxxxxxxx/
Link: https://lkml.kernel.org/r/e274344b44d5f80fa54c52f530387257fe99ec65.1731505681.git.ritesh.list@xxxxxxxxx
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/cma.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/mm/cma.c~cma-enforce-non-zero-pageblock_order-during-cma_init_reserved_mem
+++ a/mm/cma.c
@@ -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 ritesh.list@xxxxxxxxx are
cma-enforce-non-zero-pageblock_order-during-cma_init_reserved_mem.patch
