On Wed, Oct 25, 2023 at 2:31 PM Hao Sun <sunhao.th@xxxxxxxxx> wrote: > > On Tue, Oct 24, 2023 at 2:40 PM Hao Sun <sunhao.th@xxxxxxxxx> wrote: > > > > Hi, > > > > The following program can trigger a shift-out-of-bounds in > > tnum_rshift(), called by scalar32_min_max_rsh(): > > > > 0: (bc) w0 = w1 > > 1: (bf) r2 = r0 > > 2: (18) r3 = 0xd > > 4: (bc) w4 = w0 > > 5: (bf) r5 = r0 > > 6: (bf) r7 = r3 > > 7: (bf) r8 = r4 > > 8: (2f) r8 *= r5 > > 9: (cf) r5 s>>= r5 > > 10: (a6) if w8 < 0xfffffffb goto pc+10 > > 11: (1f) r7 -= r5 > > 12: (71) r6 = *(u8 *)(r1 +17) > > 13: (5f) r3 &= r8 > > 14: (74) w2 >>= 30 > > 15: (1f) r7 -= r5 > > 16: (5d) if r8 != r6 goto pc+4 > > 17: (c7) r8 s>>= 5 > > 18: (cf) r0 s>>= r0 > > 19: (7f) r0 >>= r0 > > 20: (7c) w5 >>= w8 # shift-out-bounds here > > 21: exit > > > > Here are the c macros for the above program in case anyone needs this: > > // 0: (bc) w0 = w1 > BPF_MOV32_REG(BPF_REG_0, BPF_REG_1), > // 1: (bf) r2 = r0 > BPF_MOV64_REG(BPF_REG_2, BPF_REG_0), > // 2: (18) r3 = 0xd > BPF_LD_IMM64(BPF_REG_3, 0xd), > // 4: (bc) w4 = w0 > BPF_MOV32_REG(BPF_REG_4, BPF_REG_0), > // 5: (bf) r5 = r0 > BPF_MOV64_REG(BPF_REG_5, BPF_REG_0), > // 6: (bf) r7 = r3 > BPF_MOV64_REG(BPF_REG_7, BPF_REG_3), > // 7: (bf) r8 = r4 > BPF_MOV64_REG(BPF_REG_8, BPF_REG_4), > // 8: (2f) r8 *= r5 > BPF_ALU64_REG(BPF_MUL, BPF_REG_8, BPF_REG_5), > // 9: (cf) r5 s>>= r5 > BPF_ALU64_REG(BPF_ARSH, BPF_REG_5, BPF_REG_5), > // 10: (a6) if w8 < 0xfffffffb goto pc+10 > BPF_JMP32_IMM(BPF_JLT, BPF_REG_8, 0xfffffffb, 10), > // 11: (1f) r7 -= r5 > BPF_ALU64_REG(BPF_SUB, BPF_REG_7, BPF_REG_5), > // 12: (71) r6 = *(u8 *)(r1 +17) > BPF_LDX_MEM(BPF_B, BPF_REG_6, BPF_REG_1, 17), > // 13: (5f) r3 &= r8 > BPF_ALU64_REG(BPF_AND, BPF_REG_3, BPF_REG_8), > // 14: (74) w2 >>= 30 > BPF_ALU32_IMM(BPF_RSH, BPF_REG_2, 30), > // 15: (1f) r7 -= r5 > BPF_ALU64_REG(BPF_SUB, BPF_REG_7, BPF_REG_5), > // 16: (5d) if r8 != r6 goto pc+4 > BPF_JMP_REG(BPF_JNE, BPF_REG_8, BPF_REG_6, 4), > // 17: (c7) r8 s>>= 5 > BPF_ALU64_IMM(BPF_ARSH, BPF_REG_8, 5), > // 18: (cf) r0 s>>= r0 > BPF_ALU64_REG(BPF_ARSH, BPF_REG_0, BPF_REG_0), > // 19: (7f) r0 >>= r0 > BPF_ALU64_REG(BPF_RSH, BPF_REG_0, BPF_REG_0), > // 20: (7c) w5 >>= w8 > BPF_ALU32_REG(BPF_RSH, BPF_REG_5, BPF_REG_8), > BPF_EXIT_INSN() > > > After load: > > ================================================================================ > > UBSAN: shift-out-of-bounds in kernel/bpf/tnum.c:44:9 > > shift exponent 255 is too large for 64-bit type 'long long unsigned int' > > CPU: 2 PID: 8574 Comm: bpf-test Not tainted > > 6.6.0-rc5-01400-g7c2f6c9fb91f-dirty #21 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 > > Call Trace: > > <TASK> > > __dump_stack lib/dump_stack.c:88 [inline] > > dump_stack_lvl+0x8e/0xb0 lib/dump_stack.c:106 > > ubsan_epilogue lib/ubsan.c:217 [inline] > > __ubsan_handle_shift_out_of_bounds+0x15a/0x2f0 lib/ubsan.c:387 > > tnum_rshift.cold+0x17/0x32 kernel/bpf/tnum.c:44 > > scalar32_min_max_rsh kernel/bpf/verifier.c:12999 [inline] > > adjust_scalar_min_max_vals kernel/bpf/verifier.c:13224 [inline] > > adjust_reg_min_max_vals+0x1936/0x5d50 kernel/bpf/verifier.c:13338 > > do_check kernel/bpf/verifier.c:16890 [inline] > > do_check_common+0x2f64/0xbb80 kernel/bpf/verifier.c:19563 > > do_check_main kernel/bpf/verifier.c:19626 [inline] > > bpf_check+0x65cf/0xa9e0 kernel/bpf/verifier.c:20263 > > bpf_prog_load+0x110e/0x1b20 kernel/bpf/syscall.c:2717 > > __sys_bpf+0xfcf/0x4380 kernel/bpf/syscall.c:5365 > > __do_sys_bpf kernel/bpf/syscall.c:5469 [inline] > > __se_sys_bpf kernel/bpf/syscall.c:5467 [inline] > > __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:5467 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > RIP: 0033:0x5610511e23cd > > Code: 24 80 00 00 00 48 0f 42 d0 48 89 94 24 68 0c 00 00 b8 41 01 00 > > 00 bf 05 00 00 00 ba 90 00 00 00 48 8d b44 > > RSP: 002b:00007f5357fc7820 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 > > RAX: ffffffffffffffda RBX: 0000000000000095 RCX: 00005610511e23cd > > RDX: 0000000000000090 RSI: 00007f5357fc8410 RDI: 0000000000000005 > > RBP: 0000000000000000 R08: 00007f5357fca458 R09: 00007f5350005520 > > R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000002b > > R13: 0000000d00000000 R14: 000000000000002b R15: 000000000000002b > > </TASK> > > Here is another similar one, which can probably be fixed in the same patch. Build the kernel with UBSAN and run the following repro can easily reproduce this. C reproducer: https://pastebin.com/raw/zNfHaBnj ================================================================================ UBSAN: shift-out-of-bounds in kernel/bpf/verifier.c:13049:63 shift exponent 55 is too large for 32-bit type 'int' CPU: 3 PID: 8614 Comm: poc Not tainted 6.6.0-rc5-01400-g7c2f6c9fb91f-dirty #22 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x8e/0xb0 lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:217 [inline] __ubsan_handle_shift_out_of_bounds+0x15a/0x2f0 lib/ubsan.c:387 scalar32_min_max_arsh kernel/bpf/verifier.c:13049 [inline] adjust_scalar_min_max_vals kernel/bpf/verifier.c:13237 [inline] adjust_reg_min_max_vals.cold+0x116/0x353 kernel/bpf/verifier.c:13338 do_check kernel/bpf/verifier.c:16890 [inline] do_check_common+0x2f64/0xbb80 kernel/bpf/verifier.c:19563 do_check_main kernel/bpf/verifier.c:19626 [inline] bpf_check+0x65cf/0xa9e0 kernel/bpf/verifier.c:20263 bpf_prog_load+0x110e/0x1b20 kernel/bpf/syscall.c:2717 __sys_bpf+0xfcf/0x4380 kernel/bpf/syscall.c:5365 __do_sys_bpf kernel/bpf/syscall.c:5469 [inline] __se_sys_bpf kernel/bpf/syscall.c:5467 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:5467 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x43b0a9 Code: 48 83 c4 28 c3 e8 17 1a 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 48 RSP: 002b:00007fffec705b18 EFLAGS: 00000202 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007fffec705ff8 RCX: 000000000043b0a9 RDX: 0000000000000080 RSI: 00007fffec705b30 RDI: 0000000000000005 RBP: 00007fffec705c00 R08: 0000000400000002 R09: 0000003e00000000 R10: 00000000000000fc R11: 0000000000000202 R12: 0000000000000001 R13: 00007fffec705fe8 R14: 0000000000000001 R15: 0000000000000001 </TASK>
