[PATCH 4.9 155/207] powerpc/bpf: Fix BPF_SUB when imm == 0x80000000

Greg Kroah-Hartman
2021-11-24T12:23:05Z

From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>

upstream commit 5855c4c1f415ca3ba1046e77c0b3d3dfc96c9025

We aren't handling subtraction involving an immediate value of
0x80000000 properly. Fix the same.

Fixes: 156d0e290e969c ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mpe: Fold in fix from Naveen to use imm <= 32768]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/fc4b1276eb10761fd7ce0814c8dd089da2815251.1633464148.git.naveen.n.rao@linux.vnet.ibm.com
[adjust macros to account for commits 0654186510a40e and 3a181237916310]
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/net/bpf_jit_comp64.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)

--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -363,18 +363,25 @@ static int bpf_jit_build_body(struct bpf
PPC_SUB(dst_reg, dst_reg, src_reg);
goto bpf_alu32_trunc;
case BPF_ALU | BPF_ADD | BPF_K: /* (u32) dst += (u32) imm */
- case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
case BPF_ALU64 | BPF_ADD | BPF_K: /* dst += imm */
+ if (!imm) {
+ goto bpf_alu32_trunc;
+ } else if (imm >= -32768 && imm < 32768) {
+ PPC_ADDI(dst_reg, dst_reg, IMM_L(imm));
+ } else {
+ PPC_LI32(b2p[TMP_REG_1], imm);
+ PPC_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]);
+ }
+ goto bpf_alu32_trunc;
+ case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
case BPF_ALU64 | BPF_SUB | BPF_K: /* dst -= imm */
- if (BPF_OP(code) == BPF_SUB)
- imm = -imm;
- if (imm) {
- if (imm >= -32768 && imm < 32768)
- PPC_ADDI(dst_reg, dst_reg, IMM_L(imm));
- else {
- PPC_LI32(b2p[TMP_REG_1], imm);
- PPC_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]);
- }
+ if (!imm) {
+ goto bpf_alu32_trunc;
+ } else if (imm > -32768 && imm <= 32768) {
+ PPC_ADDI(dst_reg, dst_reg, IMM_L(-imm));
+ } else {
+ PPC_LI32(b2p[TMP_REG_1], imm);
+ PPC_SUB(dst_reg, dst_reg, b2p[TMP_REG_1]);
}
goto bpf_alu32_trunc;
case BPF_ALU | BPF_MUL | BPF_X: /* (u32) dst *= (u32) src */