Commit 7e4e824b authored Jun 07, 2021 by Steven Rostedt (VMware) Committed by Greg Kroah-Hartman Jun 16, 2021

ftrace: Do not blindly read the ip address in ftrace_bug()

commit 6c14133d2d3f768e0a35128faac8aa6ed4815051 upstream.

It was reported that a bug on arm64 caused a bad ip address to be used for
updating into a nop in ftrace_init(), but the error path (rightfully)
returned -EINVAL and not -EFAULT, as the bug caused more than one error to
occur. But because -EINVAL was returned, the ftrace_bug() tried to report
what was at the location of the ip address, and read it directly. This
caused the machine to panic, as the ip was not pointing to a valid memory
address.

Instead, read the ip address with copy_from_kernel_nofault() to safely
access the memory, and if it faults, report that the address faulted,
otherwise report what was in that location.

Link: https://lore.kernel.org/lkml/20210607032329.28671-1-mark-pk.tsai@mediatek.com/



Cc: stable@vger.kernel.org
Fixes: 05736a42 ("ftrace: warn on failure to disable mcount callers")
Reported-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Tested-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 74430f3f

kernel/trace/ftrace.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -1953,12 +1953,18 @@ static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,

		static void print_ip_ins(const char fmt, const unsigned char p)
		{
		char ins[MCOUNT_INSN_SIZE];
		int i;

		if (probe_kernel_read(ins, p, MCOUNT_INSN_SIZE)) {
		printk(KERN_CONT "%s[FAULT] %px\n", fmt, p);
		return;
		}

		printk(KERN_CONT "%s", fmt);

		for (i = 0; i < MCOUNT_INSN_SIZE; i++)
		printk(KERN_CONT "%s%02x", i ? ":" : "", p[i]);
		printk(KERN_CONT "%s%02x", i ? ":" : "", ins[i]);
		}

		enum ftrace_bug_type ftrace_bug_type;