Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.15 110/177] bpf: Fix extable fixup offset. | Date | Mon, 20 Dec 2021 15:34:20 +0100 |
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From: Alexei Starovoitov <ast@kernel.org>
[ Upstream commit 433956e91200734d09958673a56df02d00a917c2 ]
The prog - start_of_ldx is the offset before the faulting ldx to the location after it, so this will be used to adjust pt_regs->ip for jumping over it and continuing, and with old temp it would have been fixed up to the wrong offset, causing crash.
Fixes: 4c5de127598e ("bpf: Emit explicit NULL pointer checks for PROBE_LDX instructions.") Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <sashal@kernel.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 9ea57389c554b..462d8e68b3f43 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1332,7 +1332,7 @@ st: if (is_imm8(insn->off)) * End result: x86 insn "mov rbx, qword ptr [rax+0x14]" * of 4 bytes will be ignored and rbx will be zero inited. */ - ex->fixup = (prog - temp) | (reg2pt_regs[dst_reg] << 8); + ex->fixup = (prog - start_of_ldx) | (reg2pt_regs[dst_reg] << 8); } break; -- 2.33.0
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