From d80773cedde2eb66e5702d383b5eff0190e7693d Mon Sep 17 00:00:00 2001 From: "Mike Rapoport (Microsoft)" Date: Thu, 3 Sep 2026 18:49:59 +0300 Subject: [PATCH] mm/execmem: handle potential allocation errors in the maple tree 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. Link: https://lore.kernel.org/20260903-execmem-rox-cache-pmd-v1-v1-2-11beb2a3d249@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Andrew Morton Assisted-by: copilot:claude-opus-5 Cc: Benjamin Tissoires Cc: Jiri Kosina Cc: Luis Chamberalin Cc: "Uladzislau Rezki (Sony)" --- mm/execmem.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/mm/execmem.c b/mm/execmem.c index ba277790e313..00dd6324cae0 100644 --- a/mm/execmem.c +++ b/mm/execmem.c @@ -149,7 +149,15 @@ static void execmem_cache_clean(struct work_struct *work) 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(struct execmem_range *range, size_t size 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)