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authorLinus Torvalds <torvalds@linux-foundation.org>2018-11-01 11:46:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-11-01 11:46:27 -0700
commit2d6bb6adb714b133db92ccd4bfc9c20f75f71f3f (patch)
treeaef040a1ee4b8b6edc5a4fa2b3c6a2c48219f27a /arch
parent7c6c54b505b8aea1782ce6a6e8f3b8297d179937 (diff)
parent6fcde90466738b84a073e4f4d18c50015ee29fb2 (diff)
downloadlinux-2d6bb6adb714b133db92ccd4bfc9c20f75f71f3f.tar.bz2
Merge tag 'stackleak-v4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull stackleak gcc plugin from Kees Cook: "Please pull this new GCC plugin, stackleak, for v4.20-rc1. This plugin was ported from grsecurity by Alexander Popov. It provides efficient stack content poisoning at syscall exit. This creates a defense against at least two classes of flaws: - Uninitialized stack usage. (We continue to work on improving the compiler to do this in other ways: e.g. unconditional zero init was proposed to GCC and Clang, and more plugin work has started too). - Stack content exposure. By greatly reducing the lifetime of valid stack contents, exposures via either direct read bugs or unknown cache side-channels become much more difficult to exploit. This complements the existing buddy and heap poisoning options, but provides the coverage for stacks. The x86 hooks are included in this series (which have been reviewed by Ingo, Dave Hansen, and Thomas Gleixner). The arm64 hooks have already been merged through the arm64 tree (written by Laura Abbott and reviewed by Mark Rutland and Will Deacon). With VLAs having been removed this release, there is no need for alloca() protection, so it has been removed from the plugin" * tag 'stackleak-v4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: arm64: Drop unneeded stackleak_check_alloca() stackleak: Allow runtime disabling of kernel stack erasing doc: self-protection: Add information about STACKLEAK feature fs/proc: Show STACKLEAK metrics in the /proc file system lkdtm: Add a test for STACKLEAK gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls
Diffstat (limited to 'arch')
-rw-r--r--arch/Kconfig7
-rw-r--r--arch/arm64/kernel/process.c22
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--arch/x86/entry/calling.h14
-rw-r--r--arch/x86/entry/entry_32.S7
-rw-r--r--arch/x86/entry/entry_64.S3
-rw-r--r--arch/x86/entry/entry_64_compat.S5
7 files changed, 37 insertions, 22 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index ed27fd262627..e1e540ffa979 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -429,6 +429,13 @@ config SECCOMP_FILTER
See Documentation/userspace-api/seccomp_filter.rst for details.
+config HAVE_ARCH_STACKLEAK
+ bool
+ help
+ An architecture should select this if it has the code which
+ fills the used part of the kernel stack with the STACKLEAK_POISON
+ value before returning from system calls.
+
config HAVE_STACKPROTECTOR
bool
help
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index ce99c58cd1f1..d9a4c2d6dd8b 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -497,25 +497,3 @@ void arch_setup_new_exec(void)
{
current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
}
-
-#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
-void __used stackleak_check_alloca(unsigned long size)
-{
- unsigned long stack_left;
- unsigned long current_sp = current_stack_pointer;
- struct stack_info info;
-
- BUG_ON(!on_accessible_stack(current, current_sp, &info));
-
- stack_left = current_sp - info.low;
-
- /*
- * There's a good chance we're almost out of stack space if this
- * is true. Using panic() over BUG() is more likely to give
- * reliable debugging output.
- */
- if (size >= stack_left)
- panic("alloca() over the kernel stack boundary\n");
-}
-EXPORT_SYMBOL(stackleak_check_alloca);
-#endif
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c51c989c19c0..ba7e3464ee92 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -129,6 +129,7 @@ config X86
select HAVE_ARCH_PREL32_RELOCATIONS
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_THREAD_STRUCT_WHITELIST
+ select HAVE_ARCH_STACKLEAK
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 708b46a54578..25e5a6bda8c3 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -329,8 +329,22 @@ For 32-bit we have the following conventions - kernel is built with
#endif
+.macro STACKLEAK_ERASE_NOCLOBBER
+#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
+ PUSH_AND_CLEAR_REGS
+ call stackleak_erase
+ POP_REGS
+#endif
+.endm
+
#endif /* CONFIG_X86_64 */
+.macro STACKLEAK_ERASE
+#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
+ call stackleak_erase
+#endif
+.endm
+
/*
* This does 'call enter_from_user_mode' unless we can avoid it based on
* kernel config or using the static jump infrastructure.
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 687e47f8a796..d309f30cf7af 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -46,6 +46,8 @@
#include <asm/frame.h>
#include <asm/nospec-branch.h>
+#include "calling.h"
+
.section .entry.text, "ax"
/*
@@ -712,6 +714,7 @@ ENTRY(ret_from_fork)
/* When we fork, we trace the syscall return in the child, too. */
movl %esp, %eax
call syscall_return_slowpath
+ STACKLEAK_ERASE
jmp restore_all
/* kernel thread */
@@ -886,6 +889,8 @@ ENTRY(entry_SYSENTER_32)
ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
"jmp .Lsyscall_32_done", X86_FEATURE_XENPV
+ STACKLEAK_ERASE
+
/* Opportunistic SYSEXIT */
TRACE_IRQS_ON /* User mode traces as IRQs on. */
@@ -997,6 +1002,8 @@ ENTRY(entry_INT80_32)
call do_int80_syscall_32
.Lsyscall_32_done:
+ STACKLEAK_ERASE
+
restore_all:
TRACE_IRQS_IRET
SWITCH_TO_ENTRY_STACK
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 4d7a2d9d44cf..ce25d84023c0 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -266,6 +266,8 @@ syscall_return_via_sysret:
* We are on the trampoline stack. All regs except RDI are live.
* We can do future final exit work right here.
*/
+ STACKLEAK_ERASE_NOCLOBBER
+
SWITCH_TO_USER_CR3_STACK scratch_reg=%rdi
popq %rdi
@@ -625,6 +627,7 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode)
* We are on the trampoline stack. All regs except RDI are live.
* We can do future final exit work right here.
*/
+ STACKLEAK_ERASE_NOCLOBBER
SWITCH_TO_USER_CR3_STACK scratch_reg=%rdi
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 7d0df78db727..8eaf8952c408 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -261,6 +261,11 @@ GLOBAL(entry_SYSCALL_compat_after_hwframe)
/* Opportunistic SYSRET */
sysret32_from_system_call:
+ /*
+ * We are not going to return to userspace from the trampoline
+ * stack. So let's erase the thread stack right now.
+ */
+ STACKLEAK_ERASE
TRACE_IRQS_ON /* User mode traces as IRQs on. */
movq RBX(%rsp), %rbx /* pt_regs->rbx */
movq RBP(%rsp), %rbp /* pt_regs->rbp */