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From: Daniel Borkmann <daniel@iogearbox.net>
To: ast@kernel.org
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: [PATCH bpf-next 2/5] bpf: Make use of probe_user_write in probe write helper
Date: Fri, 25 Oct 2019 18:37:08 +0200	[thread overview]
Message-ID: <51b9752121c1c06197291ea6b395d163313ac6ea.1572010897.git.daniel@iogearbox.net> (raw)
In-Reply-To: <cover.1572010897.git.daniel@iogearbox.net>

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>
---
 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 c3240898cc44..79919a26cd59 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


  parent reply	other threads:[~2019-10-25 16:37 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-25 16:37 [PATCH bpf-next 0/5] Fix BPF probe memory helpers Daniel Borkmann
2019-10-25 16:37 ` [PATCH bpf-next 1/5] uaccess: Add non-pagefault user-space write function Daniel Borkmann
2019-10-25 21:53   ` Andrii Nakryiko
2019-10-25 22:15     ` Daniel Borkmann
2019-10-25 22:43       ` Andrii Nakryiko
2019-10-25 16:37 ` Daniel Borkmann [this message]
2019-10-25 21:59   ` [PATCH bpf-next 2/5] bpf: Make use of probe_user_write in probe write helper Andrii Nakryiko
2019-10-25 16:37 ` [PATCH bpf-next 3/5] bpf: Add probe_read_{user,kernel} and probe_read_str_{user,kernel} helpers Daniel Borkmann
2019-10-25 22:08   ` Andrii Nakryiko
2019-10-25 22:20     ` Daniel Borkmann
2019-10-25 16:37 ` [PATCH bpf-next 4/5] bpf, samples: Use bpf_probe_read_user where appropriate Daniel Borkmann
2019-10-25 22:08   ` Andrii Nakryiko
2019-10-25 16:37 ` [PATCH bpf-next 5/5] bpf, testing: Add selftest to read/write sockaddr from user space Daniel Borkmann
2019-10-25 22:14   ` Andrii Nakryiko
2019-10-25 22:38     ` Daniel Borkmann
2019-10-25 23:35       ` Andrii Nakryiko
2019-10-25 23:36   ` Andrii Nakryiko

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