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Subject[tip:x86/core] x86/kprobes: Inline kprobe_exceptions_notify() into do_general_protection()
Commit-ID:  76dee4a72849561f6ffacc357cfd0aa33336081a
Gitweb: https://git.kernel.org/tip/76dee4a72849561f6ffacc357cfd0aa33336081a
Author: Jann Horn <jannh@google.com>
AuthorDate: Tue, 28 Aug 2018 22:14:16 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 3 Sep 2018 15:12:08 +0200

x86/kprobes: Inline kprobe_exceptions_notify() into do_general_protection()

The opaque plumbing of #GP from do_general_protection() through
notify_die() into kprobe_exceptions_notify() makes it hard to understand
what's going on.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kees Cook <keescook@chromium.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: dvyukov@google.com
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/20180828201421.157735-3-jannh@google.com

---
arch/x86/kernel/kprobes/core.c | 31 +------------------------------
arch/x86/kernel/traps.c | 10 ++++++++++
2 files changed, 11 insertions(+), 30 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index b0d1e81c96bb..467ac22691b0 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1028,42 +1028,13 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
if (fixup_exception(regs, trapnr))
return 1;

- /*
- * fixup routine could not handle it,
- * Let do_page_fault() fix it.
- */
+ /* fixup routine could not handle it. */
}

return 0;
}
NOKPROBE_SYMBOL(kprobe_fault_handler);

-/*
- * Wrapper routine for handling exceptions.
- */
-int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
- void *data)
-{
- struct die_args *args = data;
- int ret = NOTIFY_DONE;
-
- if (args->regs && user_mode(args->regs))
- return ret;
-
- if (val == DIE_GPF) {
- /*
- * To be potentially processing a kprobe fault and to
- * trust the result from kprobe_running(), we have
- * be non-preemptible.
- */
- if (!preemptible() && kprobe_running() &&
- kprobe_fault_handler(args->regs, args->trapnr))
- ret = NOTIFY_STOP;
- }
- return ret;
-}
-NOKPROBE_SYMBOL(kprobe_exceptions_notify);
-
bool arch_within_kprobe_blacklist(unsigned long addr)
{
bool is_in_entry_trampoline_section = false;
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index e6db475164ed..bf9ab1aaa175 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -556,6 +556,16 @@ do_general_protection(struct pt_regs *regs, long error_code)

tsk->thread.error_code = error_code;
tsk->thread.trap_nr = X86_TRAP_GP;
+
+ /*
+ * To be potentially processing a kprobe fault and to
+ * trust the result from kprobe_running(), we have to
+ * be non-preemptible.
+ */
+ if (!preemptible() && kprobe_running() &&
+ kprobe_fault_handler(regs, X86_TRAP_GP))
+ return;
+
if (notify_die(DIE_GPF, "general protection fault", regs, error_code,
X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP)
die("general protection fault", regs, error_code);
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