lkml.org 
[lkml]   [2020]   [Dec]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.14 155/242] x86/kprobes: Restore BTF if the single-stepping is cancelled
    Date
    From: Masami Hiramatsu <mhiramat@kernel.org>

    [ Upstream commit 78ff2733ff352175eb7f4418a34654346e1b6cd2 ]

    Fix to restore BTF if single-stepping causes a page fault and
    it is cancelled.

    Usually the BTF flag was restored when the single stepping is done
    (in resume_execution()). However, if a page fault happens on the
    single stepping instruction, the fault handler is invoked and
    the single stepping is cancelled. Thus, the BTF flag is not
    restored.

    Fixes: 1ecc798c6764 ("x86: debugctlmsr kprobes")
    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lkml.kernel.org/r/160389546985.106936.12727996109376240993.stgit@devnote2
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kernel/kprobes/core.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
    index 02665ffef0506..700d434f5bda9 100644
    --- a/arch/x86/kernel/kprobes/core.c
    +++ b/arch/x86/kernel/kprobes/core.c
    @@ -1022,6 +1022,11 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
    * So clear it by resetting the current kprobe:
    */
    regs->flags &= ~X86_EFLAGS_TF;
    + /*
    + * Since the single step (trap) has been cancelled,
    + * we need to restore BTF here.
    + */
    + restore_btf();

    /*
    * If the TF flag was set before the kprobe hit,
    --
    2.27.0


    \
     
     \ /
      Last update: 2020-12-28 14:15    [W:4.031 / U:0.580 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site