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Subject[PATCH 4.9 31/87] ARM: 8772/1: kprobes: Prohibit kprobes on get_user functions
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 0d73c3f8e7f6ee2aab1bb350f60c180f5ae21a2c upstream.

Since do_undefinstr() uses get_user to get the undefined
instruction, it can be called before kprobes processes
recursive check. This can cause an infinit recursive
exception.
Prohibit probing on get_user functions.

Fixes: 24ba613c9d6c ("ARM kprobes: core code")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm/include/asm/assembler.h | 10 ++++++++++
arch/arm/lib/getuser.S | 10 ++++++++++
2 files changed, 20 insertions(+)

--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -534,4 +534,14 @@ THUMB( orr \reg , \reg , #PSR_T_BIT )
#endif
.endm

+#ifdef CONFIG_KPROBES
+#define _ASM_NOKPROBE(entry) \
+ .pushsection "_kprobe_blacklist", "aw" ; \
+ .balign 4 ; \
+ .long entry; \
+ .popsection
+#else
+#define _ASM_NOKPROBE(entry)
+#endif
+
#endif /* __ASM_ASSEMBLER_H__ */
--- a/arch/arm/lib/getuser.S
+++ b/arch/arm/lib/getuser.S
@@ -38,6 +38,7 @@ ENTRY(__get_user_1)
mov r0, #0
ret lr
ENDPROC(__get_user_1)
+_ASM_NOKPROBE(__get_user_1)

ENTRY(__get_user_2)
check_uaccess r0, 2, r1, r2, __get_user_bad
@@ -58,6 +59,7 @@ rb .req r0
mov r0, #0
ret lr
ENDPROC(__get_user_2)
+_ASM_NOKPROBE(__get_user_2)

ENTRY(__get_user_4)
check_uaccess r0, 4, r1, r2, __get_user_bad
@@ -65,6 +67,7 @@ ENTRY(__get_user_4)
mov r0, #0
ret lr
ENDPROC(__get_user_4)
+_ASM_NOKPROBE(__get_user_4)

ENTRY(__get_user_8)
check_uaccess r0, 8, r1, r2, __get_user_bad8
@@ -78,6 +81,7 @@ ENTRY(__get_user_8)
mov r0, #0
ret lr
ENDPROC(__get_user_8)
+_ASM_NOKPROBE(__get_user_8)

#ifdef __ARMEB__
ENTRY(__get_user_32t_8)
@@ -91,6 +95,7 @@ ENTRY(__get_user_32t_8)
mov r0, #0
ret lr
ENDPROC(__get_user_32t_8)
+_ASM_NOKPROBE(__get_user_32t_8)

ENTRY(__get_user_64t_1)
check_uaccess r0, 1, r1, r2, __get_user_bad8
@@ -98,6 +103,7 @@ ENTRY(__get_user_64t_1)
mov r0, #0
ret lr
ENDPROC(__get_user_64t_1)
+_ASM_NOKPROBE(__get_user_64t_1)

ENTRY(__get_user_64t_2)
check_uaccess r0, 2, r1, r2, __get_user_bad8
@@ -114,6 +120,7 @@ rb .req r0
mov r0, #0
ret lr
ENDPROC(__get_user_64t_2)
+_ASM_NOKPROBE(__get_user_64t_2)

ENTRY(__get_user_64t_4)
check_uaccess r0, 4, r1, r2, __get_user_bad8
@@ -121,6 +128,7 @@ ENTRY(__get_user_64t_4)
mov r0, #0
ret lr
ENDPROC(__get_user_64t_4)
+_ASM_NOKPROBE(__get_user_64t_4)
#endif

__get_user_bad8:
@@ -131,6 +139,8 @@ __get_user_bad:
ret lr
ENDPROC(__get_user_bad)
ENDPROC(__get_user_bad8)
+_ASM_NOKPROBE(__get_user_bad)
+_ASM_NOKPROBE(__get_user_bad8)

.pushsection __ex_table, "a"
.long 1b, __get_user_bad

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