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bpf: Fix extable fixup offset.

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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: 4c5de12759 ("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>
This commit is contained in:
Alexei Starovoitov 2021-12-15 18:38:30 -08:00 committed by Daniel Borkmann
parent b1a7288ded
commit 433956e912
1 changed files with 1 additions and 1 deletions
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arch/x86/net/bpf_jit_comp.c
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@ -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;