FAILED: patch "[PATCH] ftrace: Do not blindly read the ip address in ftrace_bug()" failed to apply to 5.4-stable tree

FAILED: patch "[PATCH] ftrace: Do not blindly read the ip address in ftrace_bug()" failed to apply to 5.4-stable tree

[gregkh]

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6c14133d2d3f768e0a35128faac8aa6ed4815051 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Date: Mon, 7 Jun 2021 21:39:08 -0400
Subject: [PATCH] ftrace: Do not blindly read the ip address in ftrace_bug()

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: 05736a427f7e1 ("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>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 2e8a3fde7104..72ef4dccbcc4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1967,12 +1967,18 @@ 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 (copy_from_kernel_nofault(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;

Re: FAILED: patch "[PATCH] ftrace: Do not blindly read the ip address in ftrace_bug()" failed to apply to 5.4-stable tree

[Steven Rostedt]

On Sun, 13 Jun 2021 14:03:15 +0200
<gregkh@linuxfoundation.org> wrote:

> The patch below does not apply to the 5.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 

The function probe_kernel_read() was renamed to
copy_from_kernel_nofault() somewhere between 5.4 and 5.10, and since
this patch uses copy_from_kernel_nofault(), it doesn't exist in those
earlier kernels. Here's a new version using the older name (and this
should work for 4.4 through 5.10)

-- Steve

From 6c14133d2d3f768e0a35128faac8aa6ed4815051 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Date: Mon, 7 Jun 2021 21:39:08 -0400
Subject: [PATCH] ftrace: Do not blindly read the ip address in ftrace_bug()

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: 05736a427f7e1 ("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>
---
 kernel/trace/ftrace.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Index: linux-test.git/kernel/trace/ftrace.c
===================================================================
--- linux-test.git.orig/kernel/trace/ftrace.c
+++ linux-test.git/kernel/trace/ftrace.c
@@ -1953,12 +1953,18 @@ static int ftrace_hash_ipmodify_update(s
 
 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;

Re: FAILED: patch "[PATCH] ftrace: Do not blindly read the ip address in ftrace_bug()" failed to apply to 5.4-stable tree

[Greg KH]

On Sun, Jun 13, 2021 at 09:26:07PM -0400, Steven Rostedt wrote:
> On Sun, 13 Jun 2021 14:03:15 +0200
> <gregkh@linuxfoundation.org> wrote:
> 
> > The patch below does not apply to the 5.4-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> > 
> > thanks,
> > 
> > greg k-h
> > 
> > ------------------ original commit in Linus's tree ------------------
> > 
> 
> The function probe_kernel_read() was renamed to
> copy_from_kernel_nofault() somewhere between 5.4 and 5.10, and since
> this patch uses copy_from_kernel_nofault(), it doesn't exist in those
> earlier kernels. Here's a new version using the older name (and this
> should work for 4.4 through 5.10)

Now queued up, thanks.

greg k-h