This is a note to let you know that I've just added the patch titled ftrace: Do not blindly read the ip address in ftrace_bug() to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ftrace-do-not-blindly-read-the-ip-address-in-ftrace_bug.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 6c14133d2d3f768e0a35128faac8aa6ed4815051 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx> Date: Mon, 7 Jun 2021 21:39:08 -0400 Subject: ftrace: Do not blindly read the ip address in ftrace_bug() From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> 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@xxxxxxxxxxxx/ Cc: stable@xxxxxxxxxxxxxxx Fixes: 05736a427f7e1 ("ftrace: warn on failure to disable mcount callers") Reported-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx> Tested-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/trace/ftrace.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1968,12 +1968,18 @@ 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 (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; Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are queue-5.10/mips-fix-kernel-hang-under-function_graph_tracer-and.patch queue-5.10/ftrace-do-not-blindly-read-the-ip-address-in-ftrace_bug.patch