arm64: mte: Fix the stack frame size warning in mte_dump_tag_range()

With 64K page configurations, the tags array stored on the stack of the
mte_dump_tag_range() function is 2048 bytes, triggering a compiler
warning when CONFIG_FRAME_WARN is enabled. Switch to a kmalloc()
allocation via mte_allocate_tag_storage().

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: 6dd8b1a0b6cb ("arm64: mte: Dump the MTE tags in the core file")
Reported-by: kernel test robot <lkp@intel.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220401151356.1674232-1-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/elfcore.c b/arch/arm64/kernel/elfcore.c
index 3455ee4acc04cc7d9f8038e25361ca747322c721..2b3f3d0544b9808aa1240df835477dd4991b3f85 100644 (file)
--- a/arch/arm64/kernel/elfcore.c
+++ b/arch/arm64/kernel/elfcore.c
@@ -25,10 +25,11 @@ static unsigned long mte_vma_tag_dump_size(struct vm_area_struct *vma)
 static int mte_dump_tag_range(struct coredump_params *cprm,
                              unsigned long start, unsigned long end)
 {
+       int ret = 1;
        unsigned long addr;
+       void *tags = NULL;
 
        for (addr = start; addr < end; addr += PAGE_SIZE) {
-               char tags[MTE_PAGE_TAG_STORAGE];
                struct page *page = get_dump_page(addr);
 
                /*
@@ -52,13 +53,28 @@ static int mte_dump_tag_range(struct coredump_params *cprm,
                        continue;
                }
 
+               if (!tags) {
+                       tags = mte_allocate_tag_storage();
+                       if (!tags) {
+                               put_page(page);
+                               ret = 0;
+                               break;
+                       }
+               }
+
                mte_save_page_tags(page_address(page), tags);
                put_page(page);
-               if (!dump_emit(cprm, tags, MTE_PAGE_TAG_STORAGE))
-                       return 0;
+               if (!dump_emit(cprm, tags, MTE_PAGE_TAG_STORAGE)) {
+                       mte_free_tag_storage(tags);
+                       ret = 0;
+                       break;
+               }
        }
 
-       return 1;
+       if (tags)
+               mte_free_tag_storage(tags);
+
+       return ret;
 }
 
 Elf_Half elf_core_extra_phdrs(void)