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Date: Fri, 22 May 2009 08:55:15 +0400
From: Alexey Dobriyan <adobriyan@...il.com>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org,
containers@...ts.linux-foundation.org,
torvalds@...ux-foundation.org, xemul@...allels.com,
orenl@...columbia.edu, serue@...ibm.com, dave@...ux.vnet.ibm.com,
mingo@...e.hu, Alexey Dobriyan <adobriyan@...il.com>
Subject: [PATCH 21/38] C/R: i386 debug registers
Make extensive checks to not allow restoration of breakpoints
inside kernel code.
Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---
arch/x86/include/asm/ptrace.h | 5 +++++
arch/x86/kernel/ptrace.c | 8 ++++----
include/linux/kstate-image.h | 7 +++++++
kernel/kstate/kstate-x86_32.c | 26 ++++++++++++++++++++++----
4 files changed, 38 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 624f133..2b40c3c 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -243,6 +243,11 @@ extern void x86_ptrace_fork(struct task_struct *child,
#define arch_ptrace_untrace(tsk) x86_ptrace_untrace(tsk)
#define arch_ptrace_fork(child, flags) x86_ptrace_fork(child, flags)
+extern int ptrace_check_debugreg(int _32bit,
+ unsigned long dr0, unsigned long dr1,
+ unsigned long dr2, unsigned long dr3,
+ unsigned long dr6, unsigned long dr7);
+
#endif /* __KERNEL__ */
#endif /* !__ASSEMBLY__ */
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index afd2b7d..23941a7 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -465,10 +465,10 @@ static unsigned long ptrace_get_debugreg(struct task_struct *child, int n)
return 0;
}
-static int ptrace_check_debugreg(int _32bit,
- unsigned long dr0, unsigned long dr1,
- unsigned long dr2, unsigned long dr3,
- unsigned long dr6, unsigned long dr7)
+int ptrace_check_debugreg(int _32bit,
+ unsigned long dr0, unsigned long dr1,
+ unsigned long dr2, unsigned long dr3,
+ unsigned long dr6, unsigned long dr7)
{
/* Breakpoint type: 00: --x, 01: -w-, 10: undefined, 11: rw- */
unsigned int rw[4];
diff --git a/include/linux/kstate-image.h b/include/linux/kstate-image.h
index 8df5c4a..6f11b4d 100644
--- a/include/linux/kstate-image.h
+++ b/include/linux/kstate-image.h
@@ -97,6 +97,13 @@ struct kstate_image_task_struct_i386 {
__u16 gs;
__u16 ss;
+ __u32 dr0;
+ __u32 dr1;
+ __u32 dr2;
+ __u32 dr3;
+ __u32 dr6;
+ __u32 dr7;
+
__u64 tls_array[3];
} __packed;
diff --git a/kernel/kstate/kstate-x86_32.c b/kernel/kstate/kstate-x86_32.c
index 809242c..c738e16 100644
--- a/kernel/kstate/kstate-x86_32.c
+++ b/kernel/kstate/kstate-x86_32.c
@@ -106,6 +106,10 @@ int kstate_arch_check_image_task_struct(struct kstate_image_task_struct *tsk_i)
if (rv < 0)
return rv;
+ rv = ptrace_check_debugreg(1, i->dr0, i->dr1, i->dr2, i->dr3, i->dr6, i->dr7);
+ if (rv < 0)
+ return rv;
+
if (i->tls_array[0]) {
rv = check_tls((struct desc_struct *)&i->tls_array[0]);
if (rv < 0)
@@ -138,10 +142,6 @@ int kstate_arch_check_task_struct(struct task_struct *tsk)
WARN_ON(1);
return -EINVAL;
}
- if (test_tsk_thread_flag(tsk, TIF_DEBUG)) {
- WARN_ON(1);
- return -EINVAL;
- }
rb = &task_thread_info(tsk)->restart_block;
if (rb->fn != current_thread_info()->restart_block.fn) {
WARN(1, "rb->fn = %pF\n", rb->fn);
@@ -226,6 +226,13 @@ int kstate_arch_dump_task_struct(struct kstate_context *ctx, struct task_struct
i->gs = encode_segment(tsk->thread.gs);
i->ss = encode_segment(regs->ss);
+ i->dr0 = tsk->thread.debugreg0;
+ i->dr1 = tsk->thread.debugreg1;
+ i->dr2 = tsk->thread.debugreg2;
+ i->dr3 = tsk->thread.debugreg3;
+ i->dr6 = tsk->thread.debugreg6;
+ i->dr7 = tsk->thread.debugreg7;
+
BUILD_BUG_ON(sizeof(tsk->thread.tls_array[0]) != 8);
BUILD_BUG_ON(sizeof(tsk->thread.tls_array) != 3 * 8);
memcpy(i->tls_array, tsk->thread.tls_array, sizeof(i->tls_array));
@@ -261,6 +268,17 @@ static int restore_task_struct_i386(struct task_struct *tsk, struct kstate_image
tsk->thread.gs = decode_segment(i->gs);
regs->ss = decode_segment(i->ss);
+ tsk->thread.debugreg0 = i->dr0;
+ tsk->thread.debugreg1 = i->dr1;
+ tsk->thread.debugreg2 = i->dr2;
+ tsk->thread.debugreg3 = i->dr3;
+ tsk->thread.debugreg6 = i->dr6;
+ tsk->thread.debugreg7 = i->dr7;
+ if (i->dr7)
+ set_tsk_thread_flag(tsk, TIF_DEBUG);
+ else
+ clear_tsk_thread_flag(tsk, TIF_DEBUG);
+
memcpy(tsk->thread.tls_array, i->tls_array, 3 * 8);
return 0;
--
1.5.6.5
--
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