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Message-Id: <fdee1749f758de33fed9ab8227b6afaa56388b63.1466036668.git.luto@kernel.org>
Date: Wed, 15 Jun 2016 17:28:28 -0700
From: Andy Lutomirski <luto@...nel.org>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
x86@...nel.org,
Borislav Petkov <bp@...en8.de>
Cc: Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>,
Brian Gerst <brgerst@...il.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 06/13] fork: Add generic vmalloced stack support
If CONFIG_VMAP_STACK is selected, kernel stacks are allocated with
vmalloc_node.
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
arch/Kconfig | 12 ++++++++++++
kernel/fork.c | 45 +++++++++++++++++++++++++++++++++++++--------
2 files changed, 49 insertions(+), 8 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index d794384a0404..1acd262036b0 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -658,4 +658,16 @@ config ARCH_NO_COHERENT_DMA_MMAP
config CPU_NO_EFFICIENT_FFS
def_bool n
+config HAVE_ARCH_VMAP_STACK
+ def_bool n
+
+config VMAP_STACK
+ bool "Use a virtually-mapped stack"
+ depends on HAVE_ARCH_VMAP_STACK
+ ---help---
+ Enable this if you want the use virtually-mapped kernel stacks
+ with guard pages. This causes kernel stack overflows to be
+ caught immediately rather than causing difficult-to-diagnose
+ corruption.
+
source "kernel/gcov/Kconfig"
diff --git a/kernel/fork.c b/kernel/fork.c
index 59e52f2120a3..37234fa0ba9b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -158,19 +158,30 @@ void __weak arch_release_thread_info(struct thread_info *ti)
* Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
* kmemcache based allocator.
*/
-# if THREAD_SIZE >= PAGE_SIZE
+# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
int node)
{
+#ifdef CONFIG_VMAP_STACK
+ return __vmalloc_node_range(
+ THREAD_SIZE, THREAD_SIZE, VMALLOC_START, VMALLOC_END,
+ GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
+ 0, node, __builtin_return_address(0));
+#else
struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
THREAD_SIZE_ORDER);
return page ? page_address(page) : NULL;
+#endif
}
static inline void free_thread_info(struct thread_info *ti)
{
+#ifdef CONFIG_VMAP_STACK
+ vfree(ti);
+#else
free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
+#endif
}
# else
static struct kmem_cache *thread_info_cache;
@@ -215,15 +226,33 @@ static struct kmem_cache *mm_cachep;
static void account_kernel_stack(struct thread_info *ti, int account)
{
- struct zone *zone = page_zone(virt_to_page(ti));
+ struct zone *zone;
+
+ if (IS_ENABLED(CONFIG_VMAP_STACK) && !virt_addr_valid(ti)) {
+ int i;
+ struct vm_struct *vm = find_vm_area(ti);
- mod_zone_page_state(zone, NR_KERNEL_STACK,
- THREAD_SIZE / PAGE_SIZE * account);
+ WARN_ON_ONCE(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
- /* All stack pages belong to the same memcg. */
- memcg_kmem_update_page_stat(
- virt_to_page(ti), MEMCG_KERNEL_STACK,
- account * (THREAD_SIZE / PAGE_SIZE));
+ for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
+ mod_zone_page_state(page_zone(vm->pages[i]),
+ 1, account);
+ }
+
+ /* All stack pages belong to the same memcg. */
+ memcg_kmem_update_page_stat(
+ vm->pages[0], MEMCG_KERNEL_STACK,
+ account * (THREAD_SIZE / PAGE_SIZE));
+ } else {
+ zone = page_zone(virt_to_page(ti));
+ mod_zone_page_state(zone, NR_KERNEL_STACK,
+ THREAD_SIZE / PAGE_SIZE * account);
+
+ /* All stack pages belong to the same memcg. */
+ memcg_kmem_update_page_stat(
+ virt_to_page(ti), MEMCG_KERNEL_STACK,
+ account * (THREAD_SIZE / PAGE_SIZE));
+ }
}
void free_task(struct task_struct *tsk)
--
2.7.4
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