netdev - [PATCH bpf 2/3] bpf: add bpf_probe_read_{user, kernel}_str() to do_refine_retval

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Message-Id: <20200514161607.9212-3-daniel@iogearbox.net>
Date:   Thu, 14 May 2020 18:16:06 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     ast@...nel.org
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        torvalds@...ux-foundation.org, mhiramat@...nel.org,
        brendan.d.gregg@...il.com, hch@....de, john.fastabend@...il.com,
        yhs@...com, Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf 2/3] bpf: add bpf_probe_read_{user, kernel}_str() to do_refine_retval_range

Given bpf_probe_read{,str}() BPF helpers are now only available under
CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE, we need to add the drop-in
replacements of bpf_probe_read_{kernel,user}_str() to do_refine_retval_range()
as well to avoid hitting the same issue as in 849fa50662fbc ("bpf/verifier:
refine retval R0 state for bpf_get_stack helper").

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: Yonghong Song <yhs@...com>
---
 kernel/bpf/verifier.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index fa1d8245b925..ac922b0d3b00 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4340,7 +4340,9 @@ static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type,
 
 	if (ret_type != RET_INTEGER ||
 	    (func_id != BPF_FUNC_get_stack &&
-	     func_id != BPF_FUNC_probe_read_str))
+	     func_id != BPF_FUNC_probe_read_str &&
+	     func_id != BPF_FUNC_probe_read_kernel_str &&
+	     func_id != BPF_FUNC_probe_read_user_str))
 		return;
 
 	ret_reg->smax_value = meta->msize_max_value;
-- 
2.21.0