[PATCH AUTOSEL 5.7 388/388] bpf: Undo internal BPF_PROBE_MEM in BPF insns dump

Sasha Levin
2020-06-18T01:19:29Z

From: Andrii Nakryiko <andriin@fb.com>

[ Upstream commit 29fcb05bbf1a7008900bb9bee347bdbfc7171036 ]

BPF_PROBE_MEM is kernel-internal implmementation details. When dumping BPF
instructions to user-space, it needs to be replaced back with BPF_MEM mode.

Fixes: 2a02759ef5f8 ("bpf: Add support for BTF pointers to interpreter")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200613002115.1632142-1-andriin@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/syscall.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e6dee19a668..5d1d24f56d53 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2923,6 +2923,7 @@ static struct bpf_insn *bpf_insn_prepare_dump(const struct bpf_prog *prog)
struct bpf_insn *insns;
u32 off, type;
u64 imm;
+ u8 code;
int i;

insns = kmemdup(prog->insnsi, bpf_prog_insn_size(prog),
@@ -2931,21 +2932,27 @@ static struct bpf_insn *bpf_insn_prepare_dump(const struct bpf_prog *prog)
return insns;

for (i = 0; i < prog->len; i++) {
- if (insns[i].code == (BPF_JMP | BPF_TAIL_CALL)) {
+ code = insns[i].code;
+
+ if (code == (BPF_JMP | BPF_TAIL_CALL)) {
insns[i].code = BPF_JMP | BPF_CALL;
insns[i].imm = BPF_FUNC_tail_call;
/* fall-through */
}
- if (insns[i].code == (BPF_JMP | BPF_CALL) ||
- insns[i].code == (BPF_JMP | BPF_CALL_ARGS)) {
- if (insns[i].code == (BPF_JMP | BPF_CALL_ARGS))
+ if (code == (BPF_JMP | BPF_CALL) ||
+ code == (BPF_JMP | BPF_CALL_ARGS)) {
+ if (code == (BPF_JMP | BPF_CALL_ARGS))
insns[i].code = BPF_JMP | BPF_CALL;
if (!bpf_dump_raw_ok())
insns[i].imm = 0;
continue;
}
+ if (BPF_CLASS(code) == BPF_LDX && BPF_MODE(code) == BPF_PROBE_MEM) {
+ insns[i].code = BPF_LDX | BPF_SIZE(code) | BPF_MEM;
+ continue;
+ }

- if (insns[i].code != (BPF_LD | BPF_IMM | BPF_DW))
+ if (code != (BPF_LD | BPF_IMM | BPF_DW))
continue;

imm = ((u64)insns[i + 1].imm << 32) | (u32)insns[i].imm;
--
2.25.1