From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: bpf:bpf_seq_printf(): handle potentially unsafe format string better
User the proper helper for kernel or userspace addresses based on
TASK_SIZE instead of the dangerous strncpy_from_unsafe function.
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/trace/bpf_trace.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/kernel/trace/bpf_trace.c~bpf-bpf_seq_printf-handle-potentially-unsafe-format-string-better
+++ a/kernel/trace/bpf_trace.c
@@ -588,15 +588,17 @@ BPF_CALL_5(bpf_seq_printf, struct seq_fi
}
if (fmt[i] == 's') {
+ void *unsafe_ptr;
+
/* try our best to copy */
if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
err = -E2BIG;
goto out;
}
- err = strncpy_from_unsafe_strict(bufs->buf[memcpy_cnt],
- (void *) (long) args[fmt_cnt],
- MAX_SEQ_PRINTF_STR_LEN);
+ unsafe_ptr = (void *)(long)args[fmt_cnt];
+ err = strncpy_from_kernel_nofault(bufs->buf[memcpy_cnt],
+ unsafe_ptr, MAX_SEQ_PRINTF_STR_LEN);
if (err < 0)
bufs->buf[memcpy_cnt][0] = '\0';
params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt];
_
