Syzkaller hit 'general protection fault in gtp_genl_dump_pdp' bug. This bug is not a vulnerability and is reproduced only when running with root privileges. dmesg (5.10.200): gtp: GTP module loaded (pdp ctx size 104 bytes) gtp: GTP module unloaded general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 0 PID: 2782 Comm: syz-executor139 Not tainted 5.10.200-std-def-alt1 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-alt1 04/01/2014 RIP: 0010:gtp_genl_dump_pdp+0x1b1/0x790 [gtp] Code: c4 89 c6 e8 b1 07 15 e0 58 45 85 e4 0f 85 97 03 00 00 e8 72 0b 15 e0 48 8b 54 24 20 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 ac 05 00 00 48 8b 44 24 20 48 8b 08 48 89 0c 24 RSP: 0018:ffff8881146c73f8 EFLAGS: 00010213 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffffa137fa66 RDX: 0000000000000001 RSI: ffffffffa137f6be RDI: 0000000000000001 gtp: GTP module loaded (pdp ctx size 104 bytes) RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff86c4dca7 R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000001 R13: 0000000000000000 R14: ffff888133b04588 R15: 0000000000000000 FS: 00007f2ea15c5740(0000) GS:ffff888140200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2ea17686cf CR3: 000000010e56c000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: genl_lock_dumpit+0x6b/0xa0 net/netlink/genetlink.c:623 netlink_dump+0x575/0xc70 net/netlink/af_netlink.c:2271 __netlink_dump_start+0x64e/0x910 net/netlink/af_netlink.c:2376 genl_family_rcv_msg_dumpit+0x2b8/0x310 net/netlink/genetlink.c:686 genl_family_rcv_msg net/netlink/genetlink.c:780 [inline] genl_rcv_msg+0x450/0x5a0 net/netlink/genetlink.c:800 netlink_rcv_skb+0x150/0x440 net/netlink/af_netlink.c:2497 genl_rcv+0x29/0x40 net/netlink/genetlink.c:811 netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline] netlink_unicast+0x54e/0x800 net/netlink/af_netlink.c:1348 netlink_sendmsg+0x914/0xe00 net/netlink/af_netlink.c:1916 sock_sendmsg_nosec net/socket.c:651 [inline] __sock_sendmsg+0x159/0x190 net/socket.c:663 ____sys_sendmsg+0x712/0x870 net/socket.c:2376 ___sys_sendmsg+0xf8/0x170 net/socket.c:2430 __sys_sendmsg+0xea/0x1b0 net/socket.c:2459 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x62/0xc7 RIP: 0033:0x7f2ea16c2d49 Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 8b 0d ef 70 0d 00 f7 d8 64 89 01 48 RSP: 002b:00007ffc93f6ed78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000000f4240 RCX: 00007f2ea16c2d49 RDX: 0000000020040840 RSI: 0000000020000940 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007ffc93f6eb08 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000be43 R13: 00007ffc93f6ed8c R14: 00007ffc93f6eda0 R15: 00007ffc93f6ed90 Modules linked in: gtp udp_tunnel ide_cd_mod ide_gd_mod cdrom ata_generic pata_acpi ata_piix libata scsi_mod ide_pci_generic ppdev kvm_amd joydev ccp kvm irqbypass crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel bochs_drm drm_vram_helper drm_ttm_helper ttm drm_kms_helper aesni_intel crypto_simd evdev cec input_leds psmouse af_packet i2c_piix4 rc_core cryptd glue_helper serio_raw piix pcspkr intel_agp intel_gtt ide_core tiny_power_button floppy parport_pc parport qemu_fw_cfg button sch_fq_codel fuse drm dm_mod binfmt_misc efi_pstore virtio_rng rng_core ip_tables x_tables autofs4 [last unloaded: gtp] ---[ end trace 3a80aa87ef53345b ]--- RIP: 0010:gtp_genl_dump_pdp+0x1b1/0x790 [gtp] Code: c4 89 c6 e8 b1 07 15 e0 58 45 85 e4 0f 85 97 03 00 00 e8 72 0b 15 e0 48 8b 54 24 20 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 ac 05 00 00 48 8b 44 24 20 48 8b 08 48 89 0c 24 RSP: 0018:ffff8881146c73f8 EFLAGS: 00010213 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffffa137fa66 RDX: 0000000000000001 RSI: ffffffffa137f6be RDI: 0000000000000001 RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff86c4dca7 R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000001 R13: 0000000000000000 R14: ffff888133b04588 R15: 0000000000000000 FS: 00007f2ea15c5740(0000) GS:ffff888140200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2ea17686cf CR3: 000000010e56c000 CR4: 0000000000750ef0 PKRU: 55555554 note: syz-executor139[2782] exited with preempt_count 1 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: 89 c6 mov %eax,%esi 2: e8 b1 07 15 e0 callq 0xe01507b8 7: 58 pop %rax 8: 45 85 e4 test %r12d,%r12d b: 0f 85 97 03 00 00 jne 0x3a8 11: e8 72 0b 15 e0 callq 0xe0150b88 16: 48 8b 54 24 20 mov 0x20(%rsp),%rdx 1b: 48 b8 00 00 00 00 00 fc ff df movabs $0xdffffc0000000000,%rax 25: 48 c1 ea 03 shr $0x3,%rdx * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction 2d: 0f 85 ac 05 00 00 jne 0x5df 33: 48 8b 44 24 20 mov 0x20(%rsp),%rax 38: 48 8b 08 mov (%rax),%rcx 3b: 48 89 0c 24 mov %rcx,(%rsp) C reproducer: // autogenerated by syzkaller (https://github.com/google/syzkaller) #define _GNU_SOURCE #include <arpa/inet.h> #include <dirent.h> #include <endian.h> #include <errno.h> #include <fcntl.h> #include <net/if.h> #include <netinet/in.h> #include <signal.h> #include <stdarg.h> #include <stdbool.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/prctl.h> #include <sys/socket.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <sys/wait.h> #include <time.h> #include <unistd.h> #include <linux/genetlink.h> #include <linux/if_addr.h> #include <linux/if_link.h> #include <linux/in6.h> #include <linux/neighbour.h> #include <linux/net.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <linux/veth.h> static unsigned long long procid; static void sleep_ms(uint64_t ms) { usleep(ms * 1000); } static uint64_t current_time_ms(void) { struct timespec ts; if (clock_gettime(CLOCK_MONOTONIC, &ts)) exit(1); return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000; } static bool write_file(const char* file, const char* what, ...) { char buf[1024]; va_list args; va_start(args, what); vsnprintf(buf, sizeof(buf), what, args); va_end(args); buf[sizeof(buf) - 1] = 0; int len = strlen(buf); int fd = open(file, O_WRONLY | O_CLOEXEC); if (fd == -1) return false; if (write(fd, buf, len) != len) { int err = errno; close(fd); errno = err; return false; } close(fd); return true; } struct nlmsg { char* pos; int nesting; struct nlattr* nested[8]; char buf[4096]; }; static void netlink_init(struct nlmsg* nlmsg, int typ, int flags, const void* data, int size) { memset(nlmsg, 0, sizeof(*nlmsg)); struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg->buf; hdr->nlmsg_type = typ; hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags; memcpy(hdr + 1, data, size); nlmsg->pos = (char*)(hdr + 1) + NLMSG_ALIGN(size); } static void netlink_attr(struct nlmsg* nlmsg, int typ, const void* data, int size) { struct nlattr* attr = (struct nlattr*)nlmsg->pos; attr->nla_len = sizeof(*attr) + size; attr->nla_type = typ; if (size > 0) memcpy(attr + 1, data, size); nlmsg->pos += NLMSG_ALIGN(attr->nla_len); } static int netlink_send_ext(struct nlmsg* nlmsg, int sock, uint16_t reply_type, int* reply_len, bool dofail) { if (nlmsg->pos > nlmsg->buf + sizeof(nlmsg->buf) || nlmsg->nesting) exit(1); struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg->buf; hdr->nlmsg_len = nlmsg->pos - nlmsg->buf; struct sockaddr_nl addr; memset(&addr, 0, sizeof(addr)); addr.nl_family = AF_NETLINK; ssize_t n = sendto(sock, nlmsg->buf, hdr->nlmsg_len, 0, (struct sockaddr*)&addr, sizeof(addr)); if (n != (ssize_t)hdr->nlmsg_len) { if (dofail) exit(1); return -1; } n = recv(sock, nlmsg->buf, sizeof(nlmsg->buf), 0); if (reply_len) *reply_len = 0; if (n < 0) { if (dofail) exit(1); return -1; } if (n < (ssize_t)sizeof(struct nlmsghdr)) { errno = EINVAL; if (dofail) exit(1); return -1; } if (hdr->nlmsg_type == NLMSG_DONE) return 0; if (reply_len && hdr->nlmsg_type == reply_type) { *reply_len = n; return 0; } if (n < (ssize_t)(sizeof(struct nlmsghdr) + sizeof(struct nlmsgerr))) { errno = EINVAL; if (dofail) exit(1); return -1; } if (hdr->nlmsg_type != NLMSG_ERROR) { errno = EINVAL; if (dofail) exit(1); return -1; } errno = -((struct nlmsgerr*)(hdr + 1))->error; return -errno; } static int netlink_query_family_id(struct nlmsg* nlmsg, int sock, const char* family_name, bool dofail) { struct genlmsghdr genlhdr; memset(&genlhdr, 0, sizeof(genlhdr)); genlhdr.cmd = CTRL_CMD_GETFAMILY; netlink_init(nlmsg, GENL_ID_CTRL, 0, &genlhdr, sizeof(genlhdr)); netlink_attr(nlmsg, CTRL_ATTR_FAMILY_NAME, family_name, strnlen(family_name, GENL_NAMSIZ - 1) + 1); int n = 0; int err = netlink_send_ext(nlmsg, sock, GENL_ID_CTRL, &n, dofail); if (err < 0) { return -1; } uint16_t id = 0; struct nlattr* attr = (struct nlattr*)(nlmsg->buf + NLMSG_HDRLEN + NLMSG_ALIGN(sizeof(genlhdr))); for (; (char*)attr < nlmsg->buf + n; attr = (struct nlattr*)((char*)attr + NLMSG_ALIGN(attr->nla_len))) { if (attr->nla_type == CTRL_ATTR_FAMILY_ID) { id = *(uint16_t*)(attr + 1); break; } } if (!id) { errno = EINVAL; return -1; } recv(sock, nlmsg->buf, sizeof(nlmsg->buf), 0); return id; } static long syz_genetlink_get_family_id(volatile long name, volatile long sock_arg) { int fd = sock_arg; if (fd < 0) { fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC); if (fd == -1) { return -1; } } struct nlmsg nlmsg_tmp; int ret = netlink_query_family_id(&nlmsg_tmp, fd, (char*)name, false); if ((int)sock_arg < 0) close(fd); if (ret < 0) { return -1; } return ret; } static void kill_and_wait(int pid, int* status) { kill(-pid, SIGKILL); kill(pid, SIGKILL); for (int i = 0; i < 100; i++) { if (waitpid(-1, status, WNOHANG | __WALL) == pid) return; usleep(1000); } DIR* dir = opendir("/sys/fs/fuse/connections"); if (dir) { for (;;) { struct dirent* ent = readdir(dir); if (!ent) break; if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0) continue; char abort[300]; snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort", ent->d_name); int fd = open(abort, O_WRONLY); if (fd == -1) { continue; } if (write(fd, abort, 1) < 0) { } close(fd); } closedir(dir); } else { } while (waitpid(-1, status, __WALL) != pid) { } } static void setup_test() { prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0); setpgrp(); write_file("/proc/self/oom_score_adj", "1000"); } static void execute_one(void); #define WAIT_FLAGS __WALL static void loop(void) { int iter = 0; for (;; iter++) { int pid = fork(); if (pid < 0) exit(1); if (pid == 0) { setup_test(); execute_one(); exit(0); } int status = 0; uint64_t start = current_time_ms(); for (;;) { if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid) break; sleep_ms(1); if (current_time_ms() - start < 5000) continue; kill_and_wait(pid, &status); break; } } } uint64_t r[2] = {0xffffffffffffffff, 0xffffffffffffffff}; void execute_one(void) { intptr_t res = 0; memcpy((void*)0x20000140, "gtp\000", 4); syscall(__NR_delete_module, 0x20000140ul, 0x5000000ul); res = syscall(__NR_socket, 0x10ul, 3ul, 0x10); if (res != -1) r[0] = res; memcpy((void*)0x20000100, "gtp\000", 4); res = -1; res = syz_genetlink_get_family_id(0x20000100, -1); if (res != -1) r[1] = res; *(uint64_t*)0x20000940 = 0; *(uint32_t*)0x20000948 = 0; *(uint64_t*)0x20000950 = 0x20000900; *(uint64_t*)0x20000900 = 0x20000140; memcpy((void*)0x20000140, "$\000\000\000", 4); *(uint16_t*)0x20000144 = r[1]; memcpy((void*)0x20000146, "\x13\x03\xfc\xff\xff\xff\xfe\xdb\xdf\x25\x02\x00\x00\x00\x08\x00\x02\x00\x01\x00\x00\x00\x08\x00\x01\x00", 26); *(uint32_t*)0x20000160 = 0; *(uint64_t*)0x20000164 = r[1]; *(uint32_t*)0x2000016c = -1; *(uint64_t*)0x20000170 = -1; sprintf((char*)0x20000178, "0x%016llx", (long long)-1); *(uint64_t*)0x20000908 = 0x24; *(uint64_t*)0x20000958 = 1; *(uint64_t*)0x20000960 = 0; *(uint64_t*)0x20000968 = 0; *(uint32_t*)0x20000970 = 0; syscall(__NR_sendmsg, r[0], 0x20000940ul, 0x20040840ul); } int main(void) { syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul); syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul); syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul); for (procid = 0; procid < 6; procid++) { if (fork() == 0) { loop(); } } sleep(1000000); return 0; } The bug is also reproduced on the latest stable kernels with the KASAN sanitizer disabled: dmesg (6.6.13): [ 523.894617] gtp: GTP module loaded (pdp ctx size 104 bytes) [ 523.908033] gtp: GTP module unloaded [ 523.914798] BUG: kernel NULL pointer dereference, address: 0000000000000012 [ 523.915255] #PF: supervisor read access in kernel mode [ 523.915255] #PF: error_code(0x0000) - not-present page [ 523.915255] PGD 2a0b9067 P4D 2a0b9067 PUD 6ccc067 PMD 0 [ 523.915255] Oops: 0000 [#1] PREEMPT SMP NOPTI [ 523.915255] CPU: 1 PID: 9263 Comm: repro7 Not tainted 6.6.13-un-def-alt1 #1 [ 523.915255] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-alt1 04/01/2014 [ 523.915255] RIP: 0010:gtp_genl_dump_pdp+0x82/0x190 [gtp] [ 523.915255] Code: 70 00 74 21 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e 41 5f 31 d2 31 c9 31 f6 31 ff 45 31 c0 45 31 c9 c3 cc cc cc cc e8 0e 0b 57 c0 <4c> 8b 23 49 39 dc 74 22 44 89 6c 24 04 44 8b 6c 24 08 4d 85 ff 74 [ 523.915255] RSP: 0018:ffffc900017338a8 EFLAGS: 00010246 [ 523.915255] RAX: 0000000000000000 RBX: 0000000000000012 RCX: 0000000000000000 [ 523.915255] RDX: 0000000000000000 RSI: ffff88800713bb60 RDI: 0000000000000000 [ 523.915255] RBP: ffff88800632b200 R08: 0000000000000000 R09: 0000000000000000 [ 523.915255] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 523.915255] R13: 0000000000000000 R14: ffff88800713bb60 R15: 0000000000000000 [ 523.915255] FS: 00007f2bcb83f740(0000) GS:ffff88807dc80000(0000) knlGS:0000000000000000 [ 523.915255] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 523.915255] CR2: 0000000000000012 CR3: 0000000052420000 CR4: 0000000000750ee0 [ 523.915255] PKRU: 55555554 [ 523.915255] Call Trace: [ 523.915255] <TASK> [ 523.915255] ? __die+0x1f/0x70 [ 523.915255] ? page_fault_oops+0x14d/0x4a0 [ 523.915255] ? exc_page_fault+0x7b/0x180 [ 523.915255] ? asm_exc_page_fault+0x22/0x30 [ 523.915255] ? gtp_genl_dump_pdp+0x82/0x190 [gtp] [ 523.915255] ? gtp_genl_dump_pdp+0x82/0x190 [gtp] [ 523.915255] genl_dumpit+0x2f/0x90 [ 523.915255] netlink_dump+0x126/0x320 [ 523.915255] __netlink_dump_start+0x1da/0x2a0 [ 523.915255] genl_family_rcv_msg_dumpit+0x93/0x100 [ 523.915255] ? __pfx_genl_start+0x10/0x10 [ 523.915255] ? __pfx_genl_dumpit+0x10/0x10 [ 523.915255] ? __pfx_genl_done+0x10/0x10 [ 523.915255] genl_rcv_msg+0x112/0x2a0 [ 523.915255] ? __pfx_gtp_genl_dump_pdp+0x10/0x10 [gtp] [ 523.915255] ? __pfx_genl_rcv_msg+0x10/0x10 [ 523.915255] netlink_rcv_skb+0x54/0x110 [ 523.915255] genl_rcv+0x24/0x40 [ 523.915255] netlink_unicast+0x19f/0x290 [ 523.915255] netlink_sendmsg+0x250/0x4e0 [ 523.915255] ____sys_sendmsg+0x376/0x3b0 [ 523.915255] ? copy_msghdr_from_user+0x6d/0xb0 [ 523.915255] ___sys_sendmsg+0x86/0xe0 [ 523.915255] ? do_fault+0x296/0x470 [ 523.915255] ? __handle_mm_fault+0x771/0xda0 [ 523.915255] __sys_sendmsg+0x57/0xb0 [ 523.915255] do_syscall_64+0x59/0x90 [ 523.915255] ? ct_kernel_exit.isra.0+0x71/0x90 [ 523.915255] ? __ct_user_enter+0x5a/0xd0 [ 523.915255] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 523.915255] RIP: 0033:0x7f2bcb93cd49 [ 523.915255] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 8b 0d ef 70 0d 00 f7 d8 64 89 01 48 [ 523.915255] RSP: 002b:00007ffe5d907708 EFLAGS: 00000202 ORIG_RAX: 000000000000002e [ 523.915255] RAX: ffffffffffffffda RBX: 0000562f4a49f0a0 RCX: 00007f2bcb93cd49 [ 523.915255] RDX: 0000000020040840 RSI: 0000000020000940 RDI: 0000000000000003 [ 523.915255] RBP: 00007ffe5d907720 R08: 00007ffe5d907498 R09: 00007ffe5d907720 [ 523.915255] R10: 0000000000000000 R11: 0000000000000202 R12: 0000562f4a49e210 [ 523.915255] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 523.915255] </TASK> [PATCH 1/1] gtp: fix use-after-free and null-ptr-deref in gtp_genl_dump_pdp()