ARM: 8772/1: kprobes: Prohibit kprobes on get_user functions

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>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
[bwh: Backported to 3.16: Drop changes to __get_user_{8,32_t_8,64t_{1,2,4}}]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 57f0584e8d97dc7095fa6a785be27f6e71e424e0..6a1658ee2ba1963c829bab820f6a2defdbf8b5e8 100644 (file)
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -425,4 +425,14 @@ 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__ */

diff --git a/arch/arm/lib/getuser.S b/arch/arm/lib/getuser.S
index 9b06bb41fca659b9bbfc2f996e703ce2b8c315aa..75764388f8490be86e60c3ec789c04d44fd293da 100644 (file)
--- a/arch/arm/lib/getuser.S
+++ b/arch/arm/lib/getuser.S
@@ -38,6 +38,7 @@ ENTRY(__get_user_1)
        mov     r0, #0
        mov     pc, 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
        mov     pc, lr
 ENDPROC(__get_user_2)
+_ASM_NOKPROBE(__get_user_2)
 
 ENTRY(__get_user_4)
        check_uaccess r0, 4, r1, r2, __get_user_bad
@@ -65,12 +67,14 @@ ENTRY(__get_user_4)
        mov     r0, #0
        mov     pc, lr
 ENDPROC(__get_user_4)
+_ASM_NOKPROBE(__get_user_4)
 
 __get_user_bad:
        mov     r2, #0
        mov     r0, #-EFAULT
        mov     pc, lr
 ENDPROC(__get_user_bad)
+_ASM_NOKPROBE(__get_user_bad)
 
 .pushsection __ex_table, "a"
        .long   1b, __get_user_bad