diff options
authorSteven Rostedt (VMware) <>2021-06-07 21:39:08 -0400
committerSteven Rostedt (VMware) <>2021-06-08 16:44:00 -0400
commit6c14133d2d3f768e0a35128faac8aa6ed4815051 (patch)
parent824afd55e95c3cb12c55d297a0ae408be1779cc8 (diff)
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: Cc: Fixes: 05736a427f7e1 ("ftrace: warn on failure to disable mcount callers") Reported-by: Mark-PK Tsai <> Tested-by: Mark-PK Tsai <> Signed-off-by: Steven Rostedt (VMware) <>
1 files changed, 7 insertions, 1 deletions
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;