[PATCH 4.19 014/220] bpf, x32: Fix bug for BPF_JMP | {BPF_JSGT, BPF_JSLE, BPF_JSLT, BPF_JSGE}

Greg Kroah-Hartman
2019-11-22T11:13:16Z

From: Wang YanQing <udknight@gmail.com>

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 and adds a testcase in selftests/bpf for such bug.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/net/bpf_jit_comp32.c | 221 +++++++++++++++++++++++++++++++-----------
1 file changed, 168 insertions(+), 53 deletions(-)

--- 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.
*
@@ -1380,6 +1382,75 @@ static inline void emit_push_r64(const u
*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)
{
@@ -1835,11 +1906,7 @@ static int do_jit(struct bpf_prog *bpf_p
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;
@@ -1866,6 +1933,40 @@ static int do_jit(struct bpf_prog *bpf_p
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;
@@ -1926,11 +2027,7 @@ static int do_jit(struct bpf_prog *bpf_p
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;
@@ -1956,50 +2053,9 @@ static int do_jit(struct bpf_prog *bpf_p
/* 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);
@@ -2009,7 +2065,66 @@ emit_cond_jmp: /* Convert BPF opcode to
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;
}