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;