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Subject[PATCH -tip RFC 1/2] kprobes: Prohibit probing on .entry.text code
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Date
.entry.text is a code area which is used for interrupt/syscall
entries, and there are many sensitive codes.
Thus, it is better to prohibit probing on all of such codes
instead of a part of that.
Since some symbols are already registered on kprobe blacklist,
this also removes them from the blacklist.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
arch/x86/kernel/entry_32.S | 33 ---------------------------------
arch/x86/kernel/entry_64.S | 20 --------------------
kernel/kprobes.c | 10 +++++-----
3 files changed, 5 insertions(+), 58 deletions(-)

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index fd1bc1b..6d19cfb 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -315,10 +315,6 @@ ENTRY(ret_from_kernel_thread)
ENDPROC(ret_from_kernel_thread)

/*
- * Interrupt exit functions should be protected against kprobes
- */
- .pushsection .kprobes.text, "ax"
-/*
* Return to user mode is not as complex as all this looks,
* but we want the default path for a system call return to
* go as quickly as possible which is why some of this is
@@ -372,10 +368,6 @@ need_resched:
END(resume_kernel)
#endif
CFI_ENDPROC
-/*
- * End of kprobes section
- */
- .popsection

/* SYSENTER_RETURN points to after the "sysenter" instruction in
the vsyscall page. See vsyscall-sysentry.S, which defines the symbol. */
@@ -495,10 +487,6 @@ sysexit_audit:
PTGS_TO_GS_EX
ENDPROC(ia32_sysenter_target)

-/*
- * syscall stub including irq exit should be protected against kprobes
- */
- .pushsection .kprobes.text, "ax"
# system call handler stub
ENTRY(system_call)
RING0_INT_FRAME # can't unwind into user space anyway
@@ -691,10 +679,6 @@ syscall_badsys:
jmp resume_userspace
END(syscall_badsys)
CFI_ENDPROC
-/*
- * End of kprobes section
- */
- .popsection

.macro FIXUP_ESPFIX_STACK
/*
@@ -781,10 +765,6 @@ common_interrupt:
ENDPROC(common_interrupt)
CFI_ENDPROC

-/*
- * Irq entries should be protected against kprobes
- */
- .pushsection .kprobes.text, "ax"
#define BUILD_INTERRUPT3(name, nr, fn) \
ENTRY(name) \
RING0_INT_FRAME; \
@@ -961,10 +941,6 @@ ENTRY(spurious_interrupt_bug)
jmp error_code
CFI_ENDPROC
END(spurious_interrupt_bug)
-/*
- * End of kprobes section
- */
- .popsection

#ifdef CONFIG_XEN
/* Xen doesn't set %esp to be precisely what the normal sysenter
@@ -1239,11 +1215,6 @@ return_to_handler:
jmp *%ecx
#endif

-/*
- * Some functions should be protected against kprobes
- */
- .pushsection .kprobes.text, "ax"
-
ENTRY(page_fault)
RING0_EC_FRAME
ASM_CLAC
@@ -1443,7 +1414,3 @@ ENTRY(async_page_fault)
END(async_page_fault)
#endif

-/*
- * End of kprobes section
- */
- .popsection
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 603be7c..263c6cf 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -487,8 +487,6 @@ ENDPROC(native_usergs_sysret64)
TRACE_IRQS_OFF
.endm

-/* save complete stack frame */
- .pushsection .kprobes.text, "ax"
ENTRY(save_paranoid)
XCPT_FRAME 1 RDI+8
cld
@@ -517,7 +515,6 @@ ENTRY(save_paranoid)
1: ret
CFI_ENDPROC
END(save_paranoid)
- .popsection

/*
* A newly forked process directly context switches into this address.
@@ -975,10 +972,6 @@ END(interrupt)
call \func
.endm

-/*
- * Interrupt entry/exit should be protected against kprobes
- */
- .pushsection .kprobes.text, "ax"
/*
* The interrupt stubs push (~vector+0x80) onto the stack and
* then jump to common_interrupt.
@@ -1113,10 +1106,6 @@ ENTRY(retint_kernel)

CFI_ENDPROC
END(common_interrupt)
-/*
- * End of kprobes section
- */
- .popsection

/*
* APIC interrupts.
@@ -1466,11 +1455,6 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
hyperv_callback_vector hyperv_vector_handler
#endif /* CONFIG_HYPERV */

-/*
- * Some functions should be protected against kprobes
- */
- .pushsection .kprobes.text, "ax"
-
paranoidzeroentry_ist debug do_debug DEBUG_STACK
paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
paranoiderrorentry stack_segment do_stack_segment
@@ -1887,7 +1871,3 @@ ENTRY(ignore_sysret)
CFI_ENDPROC
END(ignore_sysret)

-/*
- * End of kprobes section
- */
- .popsection
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a0d367a..ec0dbc7 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -96,9 +96,6 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
static struct kprobe_blackpoint kprobe_blacklist[] = {
{"preempt_schedule",},
{"native_get_debugreg",},
- {"irq_entries_start",},
- {"common_interrupt",},
- {"mcount",}, /* mcount can be called from everywhere */
{NULL} /* Terminator */
};

@@ -1328,8 +1325,11 @@ static int __kprobes in_kprobes_functions(unsigned long addr)
{
struct kprobe_blackpoint *kb;

- if (addr >= (unsigned long)__kprobes_text_start &&
- addr < (unsigned long)__kprobes_text_end)
+ /* The __kprobes marked functions and entry code must not be probed */
+ if ((addr >= (unsigned long)__kprobes_text_start &&
+ addr < (unsigned long)__kprobes_text_end) ||
+ (addr >= (unsigned long)__entry_text_start &&
+ addr < (unsigned long)__entry_text_end))
return -EINVAL;
/*
* If there exists a kprobe_blacklist, verify and


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