Commit 433956e9 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

bpf: Fix extable fixup offset. 



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: 4c5de127 ("bpf: Emit explicit NULL pointer checks for PROBE_LDX instructions.")
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Reviewed-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent b1a7288d

arch/x86/net/bpf_jit_comp.c

+1 −1
Original line number Diff line number Diff line
@@ -1305,7 +1305,7 @@ 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;