On Wed, 2023-09-06 at 15:40 +0300, Eduard Zingerman wrote: > On Sun, 2023-09-03 at 12:55 -0700, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: fa09bc40b21a igb: disable virtualization features on 82580 > > git tree: net > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=13382fa8680000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=634e05b4025da9da > > dashboard link: https://syzkaller.appspot.com/bug?extid=291100dcb32190ec02a8 > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1529c448680000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15db0248680000 > > > > Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/7ab461d84992/disk-fa09bc40.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/3ac6d43ab2db/vmlinux-fa09bc40.xz > > kernel image: https://storage.googleapis.com/syzbot-assets/778d096a134e/bzImage-fa09bc40.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+291100dcb32190ec02a8@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN > > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > > CPU: 1 PID: 5055 Comm: syz-executor625 Not tainted 6.5.0-syzkaller-04012-gfa09bc40b21a #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023 > > RIP: 0010:bpf_prog_offload_verifier_prep+0xaa/0x170 kernel/bpf/offload.c:295 > > Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 a1 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 65 10 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 93 00 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b > > RSP: 0018:ffffc900039ff7f8 EFLAGS: 00010246 > > RAX: dffffc0000000000 RBX: ffffc9000156e000 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: ffffffff81a8cf76 RDI: ffff888021b25f10 > > RBP: ffff888021b25f00 R08: 0000000000000001 R09: fffffbfff195203d > > R10: ffffffff8ca901ef R11: 0000000000000000 R12: 0000000000000000 > > R13: 0000000000000005 R14: 0000000000000003 R15: ffffc9000156e060 > > FS: 0000555556071380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000020000100 CR3: 0000000022f6b000 CR4: 00000000003506e0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > <TASK> > > bpf_check+0x52f3/0xabd0 kernel/bpf/verifier.c:19762 > > bpf_prog_load+0x153a/0x2270 kernel/bpf/syscall.c:2708 > > __sys_bpf+0xbb6/0x4e90 kernel/bpf/syscall.c:5335 > > __do_sys_bpf kernel/bpf/syscall.c:5439 [inline] > > __se_sys_bpf kernel/bpf/syscall.c:5437 [inline] > > __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5437 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > RIP: 0033:0x7f7c0df78ea9 > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > > RSP: 002b:00007ffde3592128 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 > > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f7c0df78ea9 > > RDX: 0000000000000090 RSI: 0000000020000940 RDI: 0000000000000005 > > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000100000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > > </TASK> > > Modules linked in: > > ---[ end trace 0000000000000000 ]--- > > RIP: 0010:bpf_prog_offload_verifier_prep+0xaa/0x170 kernel/bpf/offload.c:295 > > Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 a1 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 65 10 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 93 00 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b > > RSP: 0018:ffffc900039ff7f8 EFLAGS: 00010246 > > RAX: dffffc0000000000 RBX: ffffc9000156e000 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: ffffffff81a8cf76 RDI: ffff888021b25f10 > > RBP: ffff888021b25f00 R08: 0000000000000001 R09: fffffbfff195203d > > R10: ffffffff8ca901ef R11: 0000000000000000 R12: 0000000000000000 > > R13: 0000000000000005 R14: 0000000000000003 R15: ffffc9000156e060 > > FS: 0000555556071380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000020000100 CR3: 0000000022f6b000 CR4: 00000000003506e0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > ---------------- > > Code disassembly (best guess), 3 bytes skipped: > > 0: df 48 89 fisttps -0x77(%rax) > > 3: fa cli > > 4: 48 c1 ea 03 shr $0x3,%rdx > > 8: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) > > c: 0f 85 a1 00 00 00 jne 0xb3 > > 12: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax > > 19: fc ff df > > 1c: 4c 8b 65 10 mov 0x10(%rbp),%r12 > > 20: 4c 89 e2 mov %r12,%rdx > > 23: 48 c1 ea 03 shr $0x3,%rdx > > * 27: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction > > 2b: 0f 85 93 00 00 00 jne 0xc4 > > 31: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax > > 38: fc ff df > > 3b: 4d rex.WRB > > 3c: 8b .byte 0x8b > > > > > > --- > > This report is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > > > syzbot will keep track of this issue. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > > > If the bug is already fixed, let syzbot know by replying with: > > #syz fix: exact-commit-title > > > > If you want syzbot to run the reproducer, reply with: > > #syz test: git://repo/address.git branch-or-commit-hash > > If you attach or paste a git patch, syzbot will apply it before testing. > > > > If you want to overwrite bug's subsystems, reply with: > > #syz set subsystems: new-subsystem > > (See the list of subsystem names on the web dashboard) > > > > If the bug is a duplicate of another bug, reply with: > > #syz dup: exact-subject-of-another-report > > > > If you want to undo deduplication, reply with: > > #syz undup > > > > I have an explanation of why this error occurs, but I need an advice > on how to fix it. I think the fix should look as follows: diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c index 3e4f2ec1af06..302e38bffffa 100644 --- a/kernel/bpf/offload.c +++ b/kernel/bpf/offload.c @@ -199,12 +199,11 @@ static int __bpf_prog_dev_bound_init(struct bpf_prog *prog, struct net_device *n offload->netdev = netdev; ondev = bpf_offload_find_netdev(offload->netdev); + if (bpf_prog_is_offloaded(prog->aux) && (!ondev || !ondev->offdev)) { + err = -EINVAL; + goto err_free; + } if (!ondev) { - if (bpf_prog_is_offloaded(prog->aux)) { - err = -EINVAL; - goto err_free; - } - /* When only binding to the device, explicitly * create an entry in the hashtable. */ With the following reasoning: for offloaded programs offload device should exist and it should not be a fake device create in !ondev branch. Stanislav, could you please take a look? I think this is related to commit: 2b3486bc2d23 ("bpf: Introduce device-bound XDP programs") > Then NULL pointer deference occurs in the following function from offload.c: > > int bpf_prog_offload_verifier_prep(struct bpf_prog *prog) > { > struct bpf_prog_offload *offload; > int ret = -ENODEV; > > down_read(&bpf_devs_lock); > offload = prog->aux->offload; > if (offload) { > ret = offload->offdev->ops->prepare(prog); > ^^^^^^ > this pointer is NULL > offload->dev_state = !ret; > } > up_read(&bpf_devs_lock); > > return ret; > } > > # Short explanation > > (a) call chain bpf_prog_load -> bpf_prog_dev_bound_init -> __bpf_prog_dev_bound_init > -> __bpf_offload_dev_netdev_register > might insert an instance of struct bpf_offload_netdev with {.offdev == NULL} > into hash table offload.c:offdevs; > (b) call chain bpf_prog_load -> bpf_check -> bpf_prog_offload_verifier_prep > assumes that from (prog->aux->offload != NULL) > follows (prog->aux->offload->offdev != NULL) > which is not the case because of (a). > > # Long explanation > > The reproducer generated by testbot has the following structure: > - in a loop call function execute_one(), which does the following > system calls in sequence: > - socket(AF_INET6, SOCK_RAW, IPPROTO_IGMP) = <some fd> > - ioctl(3, SIOCGIFINDEX, {ifr_name="batadv_slave_1"}) = 0 > - bpf(BPF_PROG_LOAD, > {prog_type=BPF_PROG_TYPE_XDP, ... prog_flags=0x40, prog_ifindex=29, ...}) = -1 EINVAL > (referred to as program #1 below) > - socket(AF_INET6, SOCK_RAW, IPPROTO_IGMP) = <some fd> > - ioctl(4, SIOCGIFINDEX, {ifr_name="batadv_slave_1"}) = 0 > - bpf(BPF_PROG_LOAD, > {prog_type=BPF_PROG_TYPE_XDP, ... prog_flags=0, ... prog_ifindex=29}) = -1 EINVAL > (referred to as program #2 below) > > The error occurs when second bpf call is processed. > Interestingly, if sleep(1) is inserted somewhere between first and > second bpf calls error does not occur: > > @@ -1246,6 +1246,7 @@ void execute_one(void) > *(uint32_t*)0x200009cc = 4; > syscall(__NR_bpf, /*cmd=*/5ul, /*arg=*/0x20000940ul, /*size=*/0x90ul); > res = syscall(__NR_socket, /*domain=*/0xaul, /*type=*/3ul, /*proto=*/2); > + // sleep(1); /* uncomment to hide the error */ > if (res != -1) > r[2] = res; > memcpy((void*)0x20000100, "batadv_slave_1\000\000", 16); > > ## Control flow when error occurs > > For program #1: > - bpf_prog_load(): > - bpf_prog_is_dev_bound(prog->aux) is true > - bpf_prog_dev_bound_init > - prog->aux->offload_requested is 0 (because of 0x40 prog_flags) > - __bpf_prog_dev_bound_init > - netdev is "batadv_slave_1" > - bpf_offload_find_netdev(offload->netdev) == NULL, > (this is a lookup in hash table offload.c:offdevs) > which triggers a call to __bpf_offload_dev_netdev_register > - __bpf_offload_dev_netdev_register(NULL, offload->netdev) > registers struct bpf_offload_netdev with {.offdev = NULL} > for netdev "batadv_slave_1" in offload.c:offdevs hash table. > > For program #2: > - bpf_prog_load(): > - bpf_prog_is_dev_bound(prog->aux) is true > - bpf_prog_dev_bound_init > - prog->aux->offload_requested is 1 (because of 0x0 prog_flags) > - __bpf_prog_dev_bound_init > - netdev is "batadv_slave_1" > - bpf_offload_find_netdev(offload->netdev) != NULL, > this is struct bpf_offload_netdev with {.offdev = NULL} > created for program #1 > - prog->aux->offload = struct bpf_prog_offload {.offload -> {.offdev = NULL}}, > The bpf_prog_offload remembered for prog points to bpf_offload_netdev > with .offdev == NULL. > - ... > - bpf_check > - bpf_prog_offload_verifier_prep > - prog->aux->offload != NULL, but prog->aux->offload->offdev == NULL > => null pointer deference. > > ## Control flow when error does not occur > > For program #1: > - ... all as in the previous case ... > > Some worker thread: > - kernel/bpf/core.c:bpf_prog_free_deferred, registered for program #1: > - bpf_prog_is_dev_bound(aux) is true > - bpf_prog_dev_bound_destroy > - netdev is "batadv_slave_1" > - (!ondev->offdev && list_empty(&ondev->progs)) is true > - __bpf_offload_dev_netdev_unregister > this removes struct bpf_offload_netdev with {.offdev = NULL} > from offload.c:offdevs hash table. > > For program #2: > - bpf_prog_load(): > - bpf_prog_is_dev_bound(prog->aux) is true > - bpf_prog_dev_bound_init > - prog->aux->offload_requested is 1 (because of 0x0 prog_flags) > - __bpf_prog_dev_bound_init > - netdev is "batadv_slave_1" > - bpf_offload_find_netdev(offload->netdev) == NULL > - bpf_prog_is_offloaded(prog->aux) is true > - -EINVAL is returned.
