[PATCH bpf-next v2 3/8] bpf: Make use of probe_user_write in probe write helper

[PATCH bpf-next v2 0/8] Fix BPF probe memory helpers · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
[PATCH bpf-next v2 5/8] bpf: Switch BPF probe insns to bpf_probe_read_kernel · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
Re: [PATCH bpf-next v2 5/8] bpf: Switch BPF probe insns to bpf_probe_read_kernel · Andrii Nakryiko <hidden> · 2019-10-31
[PATCH bpf-next v2 1/8] uaccess: Add non-pagefault user-space write function · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
[PATCH bpf-next v2 6/8] bpf, samples: Use bpf_probe_read_user where appropriate · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
[PATCH bpf-next v2 4/8] bpf: Add probe_read_{user,kernel} and probe_read_{user,kernel}_str helpers · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
Re: [PATCH bpf-next v2 4/8] bpf: Add probe_read_{user,kernel} and probe_read_{user,kernel}_str helpers · Andrii Nakryiko <hidden> · 2019-10-31
[PATCH bpf-next v2 7/8] bpf, testing: Convert prog tests to probe_read_{user,kernel}{,_str} helper · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
Re: [PATCH bpf-next v2 7/8] bpf, testing: Convert prog tests to probe_read_{user,kernel}{,_str} helper · Andrii Nakryiko <hidden> · 2019-10-31
[PATCH bpf-next v2 8/8] bpf, testing: Add selftest to read/write sockaddr from user space · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
[PATCH bpf-next v2 3/8] bpf: Make use of probe_user_write in probe write helper · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
[PATCH bpf-next v2 2/8] uaccess: Add strict non-pagefault kernel-space read function · Daniel Borkmann <daniel@iogearbox.net> · 2019-10-31
Re: [PATCH bpf-next v2 2/8] uaccess: Add strict non-pagefault kernel-space read function · Andrii Nakryiko <hidden> · 2019-10-31

STALE2400d REVIEWED: 1 (0M)

Revisions (3)

2019-10-25 v1 [diff vs current]
2019-10-31 v2 current
2019-11-01 v3 [diff vs current]

From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2019-10-31 01:01:06
Also in: bpf
Subsystem: bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu

Convert the bpf_probe_write_user() helper to probe_user_write() such that
writes are not attempted under KERNEL_DS anymore which is buggy as kernel
and user space pointers can have overlapping addresses. Also, given we have
the access_ok() check inside probe_user_write(), the helper doesn't need
to do it twice.

Fixes: 96ae52279594 ("bpf: Add bpf_probe_write_user BPF helper to be called in tracers")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <redacted>
---
 kernel/trace/bpf_trace.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 571c25d60710..91eb17ac4bb6 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

@@ -163,7 +163,7 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
-BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
+BPF_CALL_3(bpf_probe_write_user, void __user *, unsafe_ptr, const void *, src,
 	   u32, size)
 {
 	/*

@@ -186,10 +186,8 @@ BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
 		return -EPERM;
 	if (unlikely(!nmi_uaccess_okay()))
 		return -EPERM;
-	if (!access_ok(unsafe_ptr, size))
-		return -EPERM;
 
-	return probe_kernel_write(unsafe_ptr, src, size);
+	return probe_user_write(unsafe_ptr, src, size);
 }
 
 static const struct bpf_func_proto bpf_probe_write_user_proto = {

-- 
2.21.0

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