+ mm-execmem-handle-potential-allocation-errors-in-the-maple-tree.patch added to mm-new branch

+ mm-execmem-handle-potential-allocation-errors-in-the-maple-tree.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/execmem: handle potential allocation errors in the maple tree
has been added to the -mm mm-new branch.  Its filename is
     mm-execmem-handle-potential-allocation-errors-in-the-maple-tree.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-execmem-handle-potential-allocation-errors-in-the-maple-tree.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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and is updated there most days

------------------------------------------------------
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Subject: mm/execmem: handle potential allocation errors in the maple tree
Date: Thu, 03 Sep 2026 18:49:59 +0300

execmem_cache_clean() and execmem_cache_alloc_locked() ignore potential
allocation failures in mas_store_gfp().

While in practice they are unlikely to happen, it's better to handle those
errors and ensure the integrity of the ROX cache.

Preallocate the maple tree nodes for the stores that must not fail and
order the maple tree updates so that there won't be any failures once a
tree has been modified.

Assisted-by: copilot:claude-opus-5
Link: https://lore.kernel.org/20260903-execmem-rox-cache-pmd-v1-v1-2-11beb2a3d249@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Benjamin Tissoires <bentiss@kernel.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Luis Chamberalin <mcgrof@kernel.org>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/execmem.c |   32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

--- a/mm/execmem.c~mm-execmem-handle-potential-allocation-errors-in-the-maple-tree
+++ a/mm/execmem.c
@@ -149,7 +149,15 @@ static void execmem_cache_clean(struct w
 		if (vm && get_vm_area_size(vm) == size &&
 		    IS_ALIGNED(size, PMD_SIZE) &&
 		    IS_ALIGNED(mas.index, PMD_SIZE)) {
-			mas_store_gfp(&mas, NULL, GFP_KERNEL);
+			/*
+			 * Preallocate to ensure mas_store does not fail
+			 * If there is no memory for the tree update, bail out,
+			 * next execmem_free() might be more lucky
+			 */
+			if (mas_preallocate(&mas, NULL, GFP_KERNEL))
+				break;
+
+			mas_store_prealloc(&mas, NULL);
 			vfree(area);
 		}
 	}
@@ -219,30 +227,34 @@ static void *execmem_cache_alloc_locked(
 	addr = mas_free.index;
 	last = mas_free.last;
 
+	mas_set_range(&mas_free, addr, addr + size - 1);
+	if (mas_preallocate(&mas_free, NULL, GFP_KERNEL))
+		return NULL;
+
 	/* insert allocated size to busy_areas at range [addr, addr + size) */
 	mas_set_range(&mas_busy, addr, addr + size - 1);
 	err = mas_store_gfp(&mas_busy, (void *)addr, GFP_KERNEL);
 	if (err)
-		return NULL;
+		goto err_destroy_mas_free;
 
-	mas_store_gfp(&mas_free, NULL, GFP_KERNEL);
+	mas_store_prealloc(&mas_free, NULL);
 	if (area_size > size) {
-		void *ptr = (void *)(addr + size);
-
 		/*
 		 * re-insert remaining free size to free_areas at range
 		 * [addr + size, last]
+		 * the range matches an existing entry, so this cannot allocate
 		 */
+		ptr = (void *)(addr + size);
 		mas_set_range(&mas_free, addr + size, last);
-		err = mas_store_gfp(&mas_free, ptr, GFP_KERNEL);
-		if (err) {
-			mas_store_gfp(&mas_busy, NULL, GFP_KERNEL);
-			return NULL;
-		}
+		mas_store_gfp(&mas_free, ptr, GFP_KERNEL);
 	}
 	ptr = (void *)addr;
 
 	return ptr;
+
+err_destroy_mas_free:
+	mas_destroy(&mas_free);
+	return NULL;
 }
 
 static void *__execmem_cache_alloc(struct execmem_range *range, size_t size)
_

Patches currently in -mm which might be from rppt@kernel.org are

set_memory-add-number-of-pages-parameter-to-set_direct_map-apis.patch
mm-vmalloc-set-areas-page_order-after-allocation-succeeds.patch
mm-vmalloc-constify-vm-parameter-of-get_vm_area_page_order.patch
mm-vmalloc-make-set_area_direct_map-huge_vmap-friendly.patch
mm-execmem-use-vm_flush_reset_perms-for-rox-cache-allocations.patch
revert-arch-introduce-set_direct_map_valid_noflush.patch
docs-core-api-memory-allocation-add-kalloc_obj-and-clarify-kmalloc.patch
maintainers-add-memory-related-docs-in-core-mm-to-mm-misc-section.patch
mm-execmem-free-rox-cache-chunks-only-when-they-span-an-entire-vm-area.patch
mm-execmem-handle-potential-allocation-errors-in-the-maple-tree.patch
mm-execmem-make-sure-rox-cache-always-contains-multiples-of-pmd_size.patch
mm-vmalloc-add-define_free-for-vfree.patch
mm-execmem-use-cleanup-infrastructure-in-rox-cache-functions.patch
sh-remove-config_numa-and-realted-configuration-options.patch
sh-mm-remove-numac.patch
sh-mm-drop-allocate_pgdat.patch
sh-remove-setup_bootmem_node-and-plat_mem_setup.patch
sh-drop-dead-code-guarded-by-ifdef-config_numa.patch
sh-drop-include-asm-mmzoneh.patch
init-kconfig-drop-arch_want_numa_variable_locality.patch
sh-init-remove-call-the-memblock_set_node.patch
sh-remove-sparsemem-related-entries-from-kconfig.patch
sh-drop-include-asm-sparsememh.patch