netdev - [PATCH bpf-next v3 5/8] bpf: Switch BPF probe insns to bpf_probe_read

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Message-Id: <d2b90827837685424a4b8008dfe0460558abfada.1572649915.git.daniel@iogearbox.net>
Date:   Sat,  2 Nov 2019 00:18:00 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, ast@...nel.org, andrii.nakryiko@...il.com,
        john.fastabend@...il.com, Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf-next v3 5/8] bpf: Switch BPF probe insns to bpf_probe_read_kernel

Commit 2a02759ef5f8 ("bpf: Add support for BTF pointers to interpreter")
explicitly states that the pointer to BTF object is a pointer to a kernel
object or NULL. Therefore we should also switch to using the strict kernel
probe helper which is restricted to kernel addresses only when architectures
have non-overlapping address spaces.

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Andrii Nakryiko <andriin@...com>
---
 kernel/bpf/core.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 673f5d40a93e..76452326fd8e 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1309,11 +1309,12 @@ bool bpf_opcode_in_insntable(u8 code)
 }
 
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
-u64 __weak bpf_probe_read(void * dst, u32 size, const void * unsafe_ptr)
+u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
 {
 	memset(dst, 0, size);
 	return -EFAULT;
 }
+
 /**
  *	__bpf_prog_run - run eBPF program on a given context
  *	@regs: is the array of MAX_BPF_EXT_REG eBPF pseudo-registers
@@ -1569,9 +1570,9 @@ static u64 __no_fgcse ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u6
 	LDST(W,  u32)
 	LDST(DW, u64)
 #undef LDST
-#define LDX_PROBE(SIZEOP, SIZE)						\
-	LDX_PROBE_MEM_##SIZEOP:						\
-		bpf_probe_read(&DST, SIZE, (const void *)(long) SRC);	\
+#define LDX_PROBE(SIZEOP, SIZE)							\
+	LDX_PROBE_MEM_##SIZEOP:							\
+		bpf_probe_read_kernel(&DST, SIZE, (const void *)(long) SRC);	\
 		CONT;
 	LDX_PROBE(B,  1)
 	LDX_PROBE(H,  2)
-- 
2.21.0