[PATCH 5.12 511/700] bpf, x86: Fix extable offset calculation

[Greg Kroah-Hartman]

From: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>

[ Upstream commit 328aac5ecd119ede3633f7d17969b1ff34ccc784 ]

Commit 4c5de127598e1 ("bpf: Emit explicit NULL pointer checks for PROBE_LDX
instructions.") is emitting a couple of instructions before the actual load.
Consider those additional instructions while calculating extable offset.

Fixes: 4c5de127598e1 ("bpf: Emit explicit NULL pointer checks for PROBE_LDX instructions.")
Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20210622110026.1157847-1-ravi.bangoria@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/net/bpf_jit_comp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 7f1b3a862e14..1fb0c37e48cb 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1297,7 +1297,7 @@ st:			if (is_imm8(insn->off))
 			emit_ldx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn->off);
 			if (BPF_MODE(insn->code) == BPF_PROBE_MEM) {
 				struct exception_table_entry *ex;
-				u8 *_insn = image + proglen;
+				u8 *_insn = image + proglen + (start_of_ldx - temp);
 				s64 delta;
 
 				/* populate jmp_offset for JMP above */
-- 
2.30.2