On Sun, 13 Jun 2021 14:03:15 +0200 <gregkh@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>. > > 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@xxxxxxxxxxx> 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@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> --- 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;
