@@ -2015,8 +2015,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
case BPF_JMP | BPF_JSET | BPF_X:
case BPF_JMP32 | BPF_JSET | BPF_X: {
bool is_jmp64 = BPF_CLASS(insn->code) == BPF_JMP;
- u8 dreg_lo = dstk ? IA32_EAX : dst_lo;
- u8 dreg_hi = dstk ? IA32_EDX : dst_hi;
+ u8 dreg_lo = IA32_EAX;
+ u8 dreg_hi = IA32_EDX;
u8 sreg_lo = sstk ? IA32_ECX : src_lo;
u8 sreg_hi = sstk ? IA32_EBX : src_hi;
@@ -2028,6 +2028,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
add_2reg(0x40, IA32_EBP,
IA32_EDX),
STACK_VAR(dst_hi));
+ } else {
+ /* mov dreg_lo,dst_lo */
+ EMIT2(0x89, add_2reg(0xC0, dreg_lo, dst_lo));
+ if (is_jmp64)
+ /* mov dreg_hi,dst_hi */
+ EMIT2(0x89,
+ add_2reg(0xC0, dreg_hi, dst_hi));
}
if (sstk) {
@@ -2052,8 +2059,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
case BPF_JMP | BPF_JSET | BPF_K:
case BPF_JMP32 | BPF_JSET | BPF_K: {
bool is_jmp64 = BPF_CLASS(insn->code) == BPF_JMP;
- u8 dreg_lo = dstk ? IA32_EAX : dst_lo;
- u8 dreg_hi = dstk ? IA32_EDX : dst_hi;
+ u8 dreg_lo = IA32_EAX;
+ u8 dreg_hi = IA32_EDX;
u8 sreg_lo = IA32_ECX;
u8 sreg_hi = IA32_EBX;
u32 hi;
@@ -2066,6 +2073,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
add_2reg(0x40, IA32_EBP,
IA32_EDX),
STACK_VAR(dst_hi));
+ } else {
+ /* mov dreg_lo,dst_lo */
+ EMIT2(0x89, add_2reg(0xC0, dreg_lo, dst_lo));
+ if (is_jmp64)
+ /* mov dreg_hi,dst_hi */
+ EMIT2(0x89,
+ add_2reg(0xC0, dreg_hi, dst_hi));
}
/* mov ecx,imm32 */
The current JIT clobbers the destination register for BPF_JSET BPF_X and BPF_K by using "and" and "or" instructions. This is fine when the destination register is a temporary loaded from a register stored on the stack but not otherwise. This patch fixes the problem (for both BPF_K and BPF_X) by always loading the destination register into temporaries since BPF_JSET should not modify the destination register. This bug may not be currently triggerable as BPF_REG_AX is the only register not stored on the stack and the verifier uses it in a limited way. Fixes: 03f5781be2c7b ("bpf, x86_32: add eBPF JIT compiler for ia32") Signed-off-by: Xi Wang <xi.wang@gmail.com> Signed-off-by: Luke Nelson <luke.r.nels@gmail.com> --- arch/x86/net/bpf_jit_comp32.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-)