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    Subject[PATCH -tip v3 03/10] x86/kprobes: Prohibit probing on functions before kprobe_int3_handler()
    Date
    Prohibit probing on the functions called before kprobe_int3_handler()
    in do_int3(). More specifically, ftrace_int3_handler(),
    poke_int3_handler(), and ist_enter(). And since rcu_nmi_enter() is
    called by ist_enter(), it also should be marked as NOKPROBE_SYMBOL.

    Since those are handled before kprobe_int3_handler(), probing those
    functions can cause a breakpoint recursion and crash the kernel.

    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    ---
    arch/x86/kernel/alternative.c | 3 ++-
    arch/x86/kernel/ftrace.c | 3 ++-
    arch/x86/kernel/traps.c | 1 +
    kernel/rcu/tree.c | 2 ++
    4 files changed, 7 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
    index d458c7973c56..9a79c7808f9c 100644
    --- a/arch/x86/kernel/alternative.c
    +++ b/arch/x86/kernel/alternative.c
    @@ -11,6 +11,7 @@
    #include <linux/stop_machine.h>
    #include <linux/slab.h>
    #include <linux/kdebug.h>
    +#include <linux/kprobes.h>
    #include <asm/text-patching.h>
    #include <asm/alternative.h>
    #include <asm/sections.h>
    @@ -764,8 +765,8 @@ int poke_int3_handler(struct pt_regs *regs)
    regs->ip = (unsigned long) bp_int3_handler;

    return 1;
    -
    }
    +NOKPROBE_SYMBOL(poke_int3_handler);

    /**
    * text_poke_bp() -- update instructions on live kernel on SMP
    diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
    index 8257a59704ae..3e3789c8f8e1 100644
    --- a/arch/x86/kernel/ftrace.c
    +++ b/arch/x86/kernel/ftrace.c
    @@ -269,7 +269,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
    return ret;
    }

    -static int is_ftrace_caller(unsigned long ip)
    +static nokprobe_inline int is_ftrace_caller(unsigned long ip)
    {
    if (ip == ftrace_update_func)
    return 1;
    @@ -299,6 +299,7 @@ int ftrace_int3_handler(struct pt_regs *regs)

    return 1;
    }
    +NOKPROBE_SYMBOL(ftrace_int3_handler);

    static int ftrace_write(unsigned long ip, const char *val, int size)
    {
    diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
    index 2684a9d11e66..d26f9e9c3d83 100644
    --- a/arch/x86/kernel/traps.c
    +++ b/arch/x86/kernel/traps.c
    @@ -111,6 +111,7 @@ void ist_enter(struct pt_regs *regs)
    /* This code is a bit fragile. Test it. */
    RCU_LOCKDEP_WARN(!rcu_is_watching(), "ist_enter didn't work");
    }
    +NOKPROBE_SYMBOL(ist_enter);

    void ist_exit(struct pt_regs *regs)
    {
    diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
    index 9180158756d2..74db52a0a466 100644
    --- a/kernel/rcu/tree.c
    +++ b/kernel/rcu/tree.c
    @@ -62,6 +62,7 @@
    #include <linux/suspend.h>
    #include <linux/ftrace.h>
    #include <linux/tick.h>
    +#include <linux/kprobes.h>

    #include "tree.h"
    #include "rcu.h"
    @@ -872,6 +873,7 @@ void rcu_nmi_enter(void)
    {
    rcu_nmi_enter_common(false);
    }
    +NOKPROBE_SYMBOL(rcu_nmi_enter);

    /**
    * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
    \
     
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