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

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Message-Id: <20210712061030.898396985@linuxfoundation.org>
Date:   Mon, 12 Jul 2021 08:09:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 511/700] bpf, x86: Fix extable offset calculation

From: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>

[ 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@...ux.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Link: https://lore.kernel.org/bpf/20210622110026.1157847-1-ravi.bangoria@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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