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ftrace: Do not blindly read the ip address in ftrace_bug()

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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@mediatek.com/

Cc: stable@vger.kernel.org
Fixes: 05736a427f ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Steven Rostedt (VMware) 2021-06-07 21:39:08 -04:00 committed by Greg Kroah-Hartman
parent 74d3b20b1b
commit 9752438476
1 changed files with 7 additions and 1 deletions
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8
kernel/trace/ftrace.c
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@ -1968,12 +1968,18 @@ static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
static void print_ip_ins(const char *fmt, const unsigned char *p) static void print_ip_ins(const char *fmt, const unsigned char *p)
{ {
char ins[MCOUNT_INSN_SIZE];
int i; 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); printk(KERN_CONT "%s", fmt);
for (i = 0; i < MCOUNT_INSN_SIZE; i++) 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; enum ftrace_bug_type ftrace_bug_type;