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Date: Mon, 27 Jun 2016 15:54:35 +0200 From: Petr Mladek <pmladek@...e.com> To: Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com> Cc: Frederic Weisbecker <fweisbec@...il.com>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org, x86@...nel.org, Petr Mladek <pmladek@...e.com> Subject: [PATCH 2/4] ftrace/x86: Do not crash when reading wrong ftrace func Ftrace modifies the code on many locations. It is paranoid and avoid a kernel crash using probe_kernel_read() and probe_kernel_write(). The only exception is update_ftrace_func() where where we read the old code using memcpy(). It is true that this function is used only to modify well defined functions that are part of the ftrace API. But it might still make sense to be paranoid and be consistent with the writing side. Signed-off-by: Petr Mladek <pmladek@...e.com> --- arch/x86/kernel/ftrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 42ea69d35dfd..8305c6792ad2 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -233,7 +233,8 @@ static int update_ftrace_func(unsigned long ip, void *new) unsigned char old[MCOUNT_INSN_SIZE]; int ret; - memcpy(old, (void *)ip, MCOUNT_INSN_SIZE); + if (probe_kernel_read(old, (void *)ip, MCOUNT_INSN_SIZE)) + return -EFAULT; /* * Make sure that we replace 5-byte instruction that -- 1.8.5.6
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