linux-kernel - [PATCH 0/1] x86/kprobes: Prohibit probing of .entry

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Message-Id: <1520565492-4637-1-git-send-email-francis.deslauriers@efficios.com>
Date:   Thu,  8 Mar 2018 22:18:11 -0500
From:   Francis Deslauriers <francis.deslauriers@...icios.com>
To:     mhiramat@...nel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, peterz@...radead.org,
        mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org,
        Francis Deslauriers <francis.deslauriers@...icios.com>
Subject: [PATCH 0/1] x86/kprobes: Prohibit probing of .entry_trampoline code

Hi all,

While fuzzing the Perf kprobe interface, I found that adding a probe on
the 'entry_SYSCALL_64_trampoline' symbol will crash my 4.16-rc4
kernel(661e50bc853209e41a5c14a290ca4decc43cbfd1) on a x86_64 Qemu VM.

How to reproduce:
	echo 'p:event1 entry_SYSCALL_64_trampoline' > ./kprobe_events
	echo 1 >  events/kprobes/enable
Crash log:[1]

My understanding is that the userspace CR3 register has not yet been
replaced by the kernel's CR3, when the kprobe is triggered. This means
that the kernel addresses can not be translated, thus making the
handling of the kprobe impossible.

This can be fixed by blacklisting the .entry_trampoline section. See
patch[1/1].

Here is the config I am using[2].

Thanks,

Francis Deslauriers
EfficiOS inc.

1:http://paste.ubuntu.com/p/djnpZCzQKv/
2:http://paste.ubuntu.com/p/3jrFYt6XQB/

Francis Deslauriers (1):
  x86/kprobes: Prohibit probing of .entry_trampoline code

 arch/x86/include/asm/sections.h |  1 +
 arch/x86/kernel/kprobes/core.c  | 10 +++++++++-
 arch/x86/kernel/vmlinux.lds.S   |  2 ++
 3 files changed, 12 insertions(+), 1 deletion(-)

-- 
2.7.4