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perf/x86/hw_breakpoints: Disallow kernel breakpoints unless kprobe-safe

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Code on the kprobe blacklist doesn't want unexpected int3
exceptions. It probably doesn't want unexpected debug exceptions
either. Be safe: disallow breakpoints in nokprobes code.

On non-CONFIG_KPROBES kernels, there is no kprobe blacklist.  In
that case, disallow kernel breakpoints entirely.

It will be particularly important to keep hw breakpoints out of the
entry and NMI code once we move debug exceptions off the IST stack.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/e14b152af99640448d895e3c2a8c2d5ee19a1325.1438312874.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-07-30 20:32:40 -07:00 committed by Ingo Molnar
parent ae3f011fc2
commit e5779e8e12
3 changed files with 18 additions and 1 deletions
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15
arch/x86/kernel/hw_breakpoint.c
View File

@ -32,6 +32,7 @@
#include <linux/irqflags.h>
#include <linux/notifier.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/percpu.h>
#include <linux/kdebug.h>
#include <linux/kernel.h>
@ -243,6 +244,20 @@ static int arch_build_bp_info(struct perf_event *bp)
info->type = X86_BREAKPOINT_RW;
break;
case HW_BREAKPOINT_X:
/*
* We don't allow kernel breakpoints in places that are not
* acceptable for kprobes. On non-kprobes kernels, we don't
* allow kernel breakpoints at all.
*/
if (bp->attr.bp_addr >= TASK_SIZE_MAX) {
#ifdef CONFIG_KPROBES
if (within_kprobe_blacklist(bp->attr.bp_addr))
return -EINVAL;
#else
return -EINVAL;
#endif
}
info->type = X86_BREAKPOINT_EXECUTE;
/*
* x86 inst breakpoints need to have a specific undefined len.

2
include/linux/kprobes.h
View File

@ -267,6 +267,8 @@ extern void show_registers(struct pt_regs *regs);
extern void kprobes_inc_nmissed_count(struct kprobe *p);
extern bool arch_within_kprobe_blacklist(unsigned long addr);
extern bool within_kprobe_blacklist(unsigned long addr);
struct kprobe_insn_cache {
struct mutex mutex;
void *(*alloc)(void); /* allocate insn page */

2
kernel/kprobes.c
View File

@ -1332,7 +1332,7 @@ bool __weak arch_within_kprobe_blacklist(unsigned long addr)
addr < (unsigned long)__kprobes_text_end;
}
static bool within_kprobe_blacklist(unsigned long addr)
bool within_kprobe_blacklist(unsigned long addr)
{
struct kprobe_blacklist_entry *ent;