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Message-Id: <1523345447-10725-4-git-send-email-kpark3469@gmail.com>
Date: Tue, 10 Apr 2018 11:30:47 +0400
From: kpark3469@...il.com
To: kernel-hardening@...ts.openwall.com
Cc: catalin.marinas@....com,
keescook@...omium.org,
will.deacon@....com,
mark.rutland@....com,
james.morse@....com,
panand@...hat.com,
keun-o.park@...kmatter.ae,
psodagud@...eaurora.org,
jpoimboe@...hat.com,
mingo@...nel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 3/3] x86: usercopy: reimplement arch_within_stack_frames with unwinder
From: Sahara <keun-o.park@...kmatter.ae>
The old arch_within_stack_frames which used the frame pointer is
now reimplemented to use frame pointer unwinder apis. So the main
functionality is same as before.
Signed-off-by: Sahara <keun-o.park@...kmatter.ae>
---
arch/x86/include/asm/unwind.h | 5 ++++
arch/x86/kernel/stacktrace.c | 64 +++++++++++++++++++++++++++++++++---------
arch/x86/kernel/unwind_frame.c | 4 +--
3 files changed, 57 insertions(+), 16 deletions(-)
diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 1f86e1b..6f04906f 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -87,6 +87,11 @@ void unwind_init(void);
void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
void *orc, size_t orc_size);
#else
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+#define FRAME_HEADER_SIZE (sizeof(long) * 2)
+size_t regs_size(struct pt_regs *regs);
+#endif
+
static inline void unwind_init(void) {}
static inline
void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index ff178a0..3de1105 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -13,6 +13,33 @@
#include <asm/unwind.h>
+static inline void *get_cur_frame(struct unwind_state *state)
+{
+ void *frame = NULL;
+
+#if defined(CONFIG_UNWINDER_FRAME_POINTER)
+ if (state->regs)
+ frame = (void *)state->regs;
+ else
+ frame = (void *)state->bp;
+#endif
+ return frame;
+}
+
+static inline void *get_frame_end(struct unwind_state *state)
+{
+ void *frame_end = NULL;
+
+#if defined(CONFIG_UNWINDER_FRAME_POINTER)
+ if (state->regs) {
+ frame_end = (void *)state->regs + regs_size(state->regs);
+ } else {
+ frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
+ }
+#endif
+ return frame_end;
+}
+
/*
* Walks up the stack frames to make sure that the specified object is
* entirely contained by a single stack frame.
@@ -26,31 +53,42 @@ int arch_within_stack_frames(const void * const stack,
const void * const stackend,
const void *obj, unsigned long len)
{
-#if defined(CONFIG_FRAME_POINTER)
- const void *frame = NULL;
- const void *oldframe;
-
- oldframe = __builtin_frame_address(2);
- if (oldframe)
- frame = __builtin_frame_address(3);
+#if defined(CONFIG_UNWINDER_FRAME_POINTER)
+ struct unwind_state state;
+ void *prev_frame_end = NULL;
/*
* low ----------------------------------------------> high
* [saved bp][saved ip][args][local vars][saved bp][saved ip]
* ^----------------^
* allow copies only within here
+ *
+ * Skip 3 non-inlined frames: arch_within_stack_frames(),
+ * check_stack_object() and __check_object_size().
+ *
*/
- while (stack <= frame && frame < stackend) {
+ unsigned int discard_frames = 3;
+
+ for (unwind_start(&state, current, NULL, NULL); !unwind_done(&state);
+ unwind_next_frame(&state)) {
/*
* If obj + len extends past the last frame, this
* check won't pass and the next frame will be 0,
* causing us to bail out and correctly report
* the copy as invalid.
*/
- if (obj + len <= frame)
- return obj >= oldframe + 2 * sizeof(void *) ?
- GOOD_FRAME : BAD_STACK;
- oldframe = frame;
- frame = *(const void * const *)frame;
+ if (discard_frames) {
+ discard_frames--;
+ } else {
+ void *frame = get_cur_frame(&state);
+
+ if (!frame || !prev_frame_end)
+ return NOT_STACK;
+ if (obj + len <= frame)
+ return obj >= prev_frame_end ?
+ GOOD_FRAME : BAD_STACK;
+ }
+ /* save current frame end before move to next frame */
+ prev_frame_end = get_frame_end(&state);
}
return BAD_STACK;
#else
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 3dc26f9..c8bfa5c 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -8,8 +8,6 @@
#include <asm/stacktrace.h>
#include <asm/unwind.h>
-#define FRAME_HEADER_SIZE (sizeof(long) * 2)
-
unsigned long unwind_get_return_address(struct unwind_state *state)
{
if (unwind_done(state))
@@ -69,7 +67,7 @@ static void unwind_dump(struct unwind_state *state)
}
}
-static size_t regs_size(struct pt_regs *regs)
+size_t regs_size(struct pt_regs *regs)
{
/* x86_32 regs from kernel mode are two words shorter: */
if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
--
2.7.4
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