From aec6ce59133edc4ac04f7d4e2556fdf047becb62 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Mon, 8 Jun 2020 21:34:33 -0700
Subject: [PATCH] bpf: handle the compat string in bpf_trace_copy_string better
User the proper helper for kernel or userspace addresses based on
TASK_SIZE instead of the dangerous strncpy_from_unsafe function.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200521152301.2587579-13-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/trace/bpf_trace.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 60e82c7b81226..a2efbdad434b5 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -334,8 +334,11 @@ static void bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype,
switch (fmt_ptype) {
case 's':
#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
- strncpy_from_unsafe(buf, unsafe_ptr, bufsz);
- break;
+ if ((unsigned long)unsafe_ptr < TASK_SIZE) {
+ strncpy_from_user_nofault(buf, user_ptr, bufsz);
+ break;
+ }
+ fallthrough;
#endif
case 'k':
strncpy_from_kernel_nofault(buf, unsafe_ptr, bufsz);
--
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