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x86/kprobes: Restore BTF if the single-stepping is cancelled 

[ Upstream commit 78ff2733ff ]

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: 1ecc798c67 ("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>
5.4-rM2-2.2.x-imx-squashed
Masami Hiramatsu 2020-10-28 23:31:10 +09:00 committed by Greg Kroah-Hartman
parent 353b19562a
commit 070c57885e
1 changed files with 5 additions and 0 deletions
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5
arch/x86/kernel/kprobes/core.c
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@ -1019,6 +1019,11 @@ 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,