commit 711aef1bbf88212a21f7103e88f397b47a528805 upstream.

The current method to compare 64-bit numbers for conditional jump is:

1) Compare the high 32-bit first.

2) If the high 32-bit isn't the same, then goto step 4.

3) Compare the low 32-bit.

4) Check the desired condition.

This method is right for unsigned comparison, but it is buggy for signed comparison, because it does signed comparison for low 32-bit too.

There is only one sign bit in 64-bit number, that is the MSB in the 64-bit number, it is wrong to treat low 32-bit as signed number and do the signed comparison for it.

This patch fixes the bug.

Note: The original commit adds a testcase in selftests/bpf for such bug, this backport patch doesn't include the testcase, because the testcase needs another upstream commit.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=205469 Reported-by: Tony Ambardar itugrok@yahoo.com Cc: Tony Ambardar itugrok@yahoo.com Cc: stable@vger.kernel.org #v4.19 Signed-off-by: Wang YanQing udknight@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net --- arch/x86/net/bpf_jit_comp32.c | 221 ++++++++++++++++++++++++++-------- 1 file changed, 168 insertions(+), 53 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 8f6cc71e0848..85f1f11a45bf 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -117,6 +117,8 @@ static bool is_simm32(s64 value) #define IA32_JLE 0x7E #define IA32_JG 0x7F

+#define COND_JMP_OPCODE_INVALID (0xFF) + /* * Map eBPF registers to IA32 32bit registers or stack scratch space. * @@ -1613,6 +1615,75 @@ static inline void emit_push_r64(const u8 src[], u8 **pprog) *pprog = prog; }

+static u8 get_cond_jmp_opcode(const u8 op, bool is_cmp_lo) +{ + u8 jmp_cond; + + /* Convert BPF opcode to x86 */ + switch (op) { + case BPF_JEQ: + jmp_cond = IA32_JE; + break; + case BPF_JSET: + case BPF_JNE: + jmp_cond = IA32_JNE; + break; + case BPF_JGT: + /* GT is unsigned '>', JA in x86 */ + jmp_cond = IA32_JA; + break; + case BPF_JLT: + /* LT is unsigned '<', JB in x86 */ + jmp_cond = IA32_JB; + break; + case BPF_JGE: + /* GE is unsigned '>=', JAE in x86 */ + jmp_cond = IA32_JAE; + break; + case BPF_JLE: + /* LE is unsigned '<=', JBE in x86 */ + jmp_cond = IA32_JBE; + break; + case BPF_JSGT: + if (!is_cmp_lo) + /* Signed '>', GT in x86 */ + jmp_cond = IA32_JG; + else + /* GT is unsigned '>', JA in x86 */ + jmp_cond = IA32_JA; + break; + case BPF_JSLT: + if (!is_cmp_lo) + /* Signed '<', LT in x86 */ + jmp_cond = IA32_JL; + else + /* LT is unsigned '<', JB in x86 */ + jmp_cond = IA32_JB; + break; + case BPF_JSGE: + if (!is_cmp_lo) + /* Signed '>=', GE in x86 */ + jmp_cond = IA32_JGE; + else + /* GE is unsigned '>=', JAE in x86 */ + jmp_cond = IA32_JAE; + break; + case BPF_JSLE: + if (!is_cmp_lo) + /* Signed '<=', LE in x86 */ + jmp_cond = IA32_JLE; + else + /* LE is unsigned '<=', JBE in x86 */ + jmp_cond = IA32_JBE; + break; + default: /* to silence GCC warning */ + jmp_cond = COND_JMP_OPCODE_INVALID; + break; + } + + return jmp_cond; +} + static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, int oldproglen, struct jit_context *ctx) { @@ -2068,11 +2139,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, case BPF_JMP | BPF_JGT | BPF_X: case BPF_JMP | BPF_JLT | BPF_X: case BPF_JMP | BPF_JGE | BPF_X: - case BPF_JMP | BPF_JLE | BPF_X: - case BPF_JMP | BPF_JSGT | BPF_X: - case BPF_JMP | BPF_JSLE | BPF_X: - case BPF_JMP | BPF_JSLT | BPF_X: - case BPF_JMP | BPF_JSGE | BPF_X: { + case BPF_JMP | BPF_JLE | BPF_X: { u8 dreg_lo = dstk ? IA32_EAX : dst_lo; u8 dreg_hi = dstk ? IA32_EDX : dst_hi; u8 sreg_lo = sstk ? IA32_ECX : src_lo; @@ -2099,6 +2166,40 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, EMIT2(0x39, add_2reg(0xC0, dreg_lo, sreg_lo)); goto emit_cond_jmp; } + case BPF_JMP | BPF_JSGT | BPF_X: + case BPF_JMP | BPF_JSLE | BPF_X: + case BPF_JMP | BPF_JSLT | BPF_X: + case BPF_JMP | BPF_JSGE | BPF_X: { + u8 dreg_lo = dstk ? IA32_EAX : dst_lo; + u8 dreg_hi = dstk ? IA32_EDX : dst_hi; + u8 sreg_lo = sstk ? IA32_ECX : src_lo; + u8 sreg_hi = sstk ? IA32_EBX : src_hi; + + if (dstk) { + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EAX), + STACK_VAR(dst_lo)); + EMIT3(0x8B, + add_2reg(0x40, IA32_EBP, + IA32_EDX), + STACK_VAR(dst_hi)); + } + + if (sstk) { + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_ECX), + STACK_VAR(src_lo)); + EMIT3(0x8B, + add_2reg(0x40, IA32_EBP, + IA32_EBX), + STACK_VAR(src_hi)); + } + + /* cmp dreg_hi,sreg_hi */ + EMIT2(0x39, add_2reg(0xC0, dreg_hi, sreg_hi)); + EMIT2(IA32_JNE, 10); + /* cmp dreg_lo,sreg_lo */ + EMIT2(0x39, add_2reg(0xC0, dreg_lo, sreg_lo)); + goto emit_cond_jmp_signed; + } case BPF_JMP | BPF_JSET | BPF_X: { u8 dreg_lo = dstk ? IA32_EAX : dst_lo; u8 dreg_hi = dstk ? IA32_EDX : dst_hi; @@ -2159,11 +2260,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, case BPF_JMP | BPF_JGT | BPF_K: case BPF_JMP | BPF_JLT | BPF_K: case BPF_JMP | BPF_JGE | BPF_K: - case BPF_JMP | BPF_JLE | BPF_K: - case BPF_JMP | BPF_JSGT | BPF_K: - case BPF_JMP | BPF_JSLE | BPF_K: - case BPF_JMP | BPF_JSLT | BPF_K: - case BPF_JMP | BPF_JSGE | BPF_K: { + case BPF_JMP | BPF_JLE | BPF_K: { u32 hi; u8 dreg_lo = dstk ? IA32_EAX : dst_lo; u8 dreg_hi = dstk ? IA32_EDX : dst_hi; @@ -2189,50 +2286,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, /* cmp dreg_lo,sreg_lo */ EMIT2(0x39, add_2reg(0xC0, dreg_lo, sreg_lo));

-emit_cond_jmp: /* Convert BPF opcode to x86 */ - switch (BPF_OP(code)) { - case BPF_JEQ: - jmp_cond = IA32_JE; - break; - case BPF_JSET: - case BPF_JNE: - jmp_cond = IA32_JNE; - break; - case BPF_JGT: - /* GT is unsigned '>', JA in x86 */ - jmp_cond = IA32_JA; - break; - case BPF_JLT: - /* LT is unsigned '<', JB in x86 */ - jmp_cond = IA32_JB; - break; - case BPF_JGE: - /* GE is unsigned '>=', JAE in x86 */ - jmp_cond = IA32_JAE; - break; - case BPF_JLE: - /* LE is unsigned '<=', JBE in x86 */ - jmp_cond = IA32_JBE; - break; - case BPF_JSGT: - /* Signed '>', GT in x86 */ - jmp_cond = IA32_JG; - break; - case BPF_JSLT: - /* Signed '<', LT in x86 */ - jmp_cond = IA32_JL; - break; - case BPF_JSGE: - /* Signed '>=', GE in x86 */ - jmp_cond = IA32_JGE; - break; - case BPF_JSLE: - /* Signed '<=', LE in x86 */ - jmp_cond = IA32_JLE; - break; - default: /* to silence GCC warning */ +emit_cond_jmp: jmp_cond = get_cond_jmp_opcode(BPF_OP(code), false); + if (jmp_cond == COND_JMP_OPCODE_INVALID) return -EFAULT; - } jmp_offset = addrs[i + insn->off] - addrs[i]; if (is_imm8(jmp_offset)) { EMIT2(jmp_cond, jmp_offset); @@ -2242,7 +2298,66 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, pr_err("cond_jmp gen bug %llx\n", jmp_offset); return -EFAULT; } + break; + } + case BPF_JMP | BPF_JSGT | BPF_K: + case BPF_JMP | BPF_JSLE | BPF_K: + case BPF_JMP | BPF_JSLT | BPF_K: + case BPF_JMP | BPF_JSGE | BPF_K: { + u8 dreg_lo = dstk ? IA32_EAX : dst_lo; + u8 dreg_hi = dstk ? IA32_EDX : dst_hi; + u8 sreg_lo = IA32_ECX; + u8 sreg_hi = IA32_EBX; + u32 hi;

+ if (dstk) { + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EAX), + STACK_VAR(dst_lo)); + EMIT3(0x8B, + add_2reg(0x40, IA32_EBP, + IA32_EDX), + STACK_VAR(dst_hi)); + } + + /* mov ecx,imm32 */ + EMIT2_off32(0xC7, add_1reg(0xC0, IA32_ECX), imm32); + hi = imm32 & (1 << 31) ? (u32)~0 : 0; + /* mov ebx,imm32 */ + EMIT2_off32(0xC7, add_1reg(0xC0, IA32_EBX), hi); + /* cmp dreg_hi,sreg_hi */ + EMIT2(0x39, add_2reg(0xC0, dreg_hi, sreg_hi)); + EMIT2(IA32_JNE, 10); + /* cmp dreg_lo,sreg_lo */ + EMIT2(0x39, add_2reg(0xC0, dreg_lo, sreg_lo)); + + /* + * For simplicity of branch offset computation, + * let's use fixed jump coding here. + */ +emit_cond_jmp_signed: /* Check the condition for low 32-bit comparison */ + jmp_cond = get_cond_jmp_opcode(BPF_OP(code), true); + if (jmp_cond == COND_JMP_OPCODE_INVALID) + return -EFAULT; + jmp_offset = addrs[i + insn->off] - addrs[i] + 8; + if (is_simm32(jmp_offset)) { + EMIT2_off32(0x0F, jmp_cond + 0x10, jmp_offset); + } else { + pr_err("cond_jmp gen bug %llx\n", jmp_offset); + return -EFAULT; + } + EMIT2(0xEB, 6); + + /* Check the condition for high 32-bit comparison */ + jmp_cond = get_cond_jmp_opcode(BPF_OP(code), false); + if (jmp_cond == COND_JMP_OPCODE_INVALID) + return -EFAULT; + jmp_offset = addrs[i + insn->off] - addrs[i]; + if (is_simm32(jmp_offset)) { + EMIT2_off32(0x0F, jmp_cond + 0x10, jmp_offset); + } else { + pr_err("cond_jmp gen bug %llx\n", jmp_offset); + return -EFAULT; + } break; } case BPF_JMP | BPF_JA: