| From 09292b480c30f29e07e16bfe210105a9f7b9d470 Mon Sep 17 00:00:00 2001 |
| From: Kees Cook <keescook@chromium.org> |
| Date: Tue, 17 Sep 2019 11:00:25 -0700 |
| Subject: [PATCH] usercopy: Avoid HIGHMEM pfn warning |
| |
| commit 314eed30ede02fa925990f535652254b5bad6b65 upstream. |
| |
| When running on a system with >512MB RAM with a 32-bit kernel built with: |
| |
| CONFIG_DEBUG_VIRTUAL=y |
| CONFIG_HIGHMEM=y |
| CONFIG_HARDENED_USERCOPY=y |
| |
| all execve()s will fail due to argv copying into kmap()ed pages, and on |
| usercopy checking the calls ultimately of virt_to_page() will be looking |
| for "bad" kmap (highmem) pointers due to CONFIG_DEBUG_VIRTUAL=y: |
| |
| ------------[ cut here ]------------ |
| kernel BUG at ../arch/x86/mm/physaddr.c:83! |
| invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC |
| CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.3.0-rc8 #6 |
| Hardware name: Dell Inc. Inspiron 1318/0C236D, BIOS A04 01/15/2009 |
| EIP: __phys_addr+0xaf/0x100 |
| ... |
| Call Trace: |
| __check_object_size+0xaf/0x3c0 |
| ? __might_sleep+0x80/0xa0 |
| copy_strings+0x1c2/0x370 |
| copy_strings_kernel+0x2b/0x40 |
| __do_execve_file+0x4ca/0x810 |
| ? kmem_cache_alloc+0x1c7/0x370 |
| do_execve+0x1b/0x20 |
| ... |
| |
| The check is from arch/x86/mm/physaddr.c: |
| |
| VIRTUAL_BUG_ON((phys_addr >> PAGE_SHIFT) > max_low_pfn); |
| |
| Due to the kmap() in fs/exec.c: |
| |
| kaddr = kmap(kmapped_page); |
| ... |
| if (copy_from_user(kaddr+offset, str, bytes_to_copy)) ... |
| |
| Now we can fetch the correct page to avoid the pfn check. In both cases, |
| hardened usercopy will need to walk the page-span checker (if enabled) |
| to do sanity checking. |
| |
| Reported-by: Randy Dunlap <rdunlap@infradead.org> |
| Tested-by: Randy Dunlap <rdunlap@infradead.org> |
| Fixes: f5509cc18daa ("mm: Hardened usercopy") |
| Cc: Matthew Wilcox <willy@infradead.org> |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Kees Cook <keescook@chromium.org> |
| Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> |
| Link: https://lore.kernel.org/r/201909171056.7F2FFD17@keescook |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/mm/usercopy.c b/mm/usercopy.c |
| index 98e924864554..660717a1ea5c 100644 |
| --- a/mm/usercopy.c |
| +++ b/mm/usercopy.c |
| @@ -11,6 +11,7 @@ |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/mm.h> |
| +#include <linux/highmem.h> |
| #include <linux/slab.h> |
| #include <linux/sched.h> |
| #include <linux/sched/task.h> |
| @@ -227,7 +228,12 @@ static inline void check_heap_object(const void *ptr, unsigned long n, |
| if (!virt_addr_valid(ptr)) |
| return; |
| |
| - page = virt_to_head_page(ptr); |
| + /* |
| + * When CONFIG_HIGHMEM=y, kmap_to_page() will give either the |
| + * highmem page or fallback to virt_to_page(). The following |
| + * is effectively a highmem-aware virt_to_head_page(). |
| + */ |
| + page = compound_head(kmap_to_page((void *)ptr)); |
| |
| if (PageSlab(page)) { |
| /* Check slab allocator for flags and size. */ |
| -- |
| 2.7.4 |
| |