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SubjectRe: [PATCH] arm64: ftrace: don't dereference a probably invalid address
On Mon, 7 Jun 2021 22:15:22 +0800
Mark-PK Tsai <mark-pk.tsai@mediatek.com> wrote:

> And the crash is becuase kernel trying to read *rec->ip in print_ip_ins() if
> ftrace_bug() get error code -EINVAL.

Right, so the actual fix should be something like this:

[ not tested, nor even compiled ]

-- Steve


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)", 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;
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