Syzkaller hit 'memory leak in prepare_creds' bug. executing program executing program BUG: memory leak unreferenced object 0xffff88800ebaf500 (size 168): comm "syz-executor424", pid 261, jiffies 4294816223 (age 21.671s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<0000000091ae1494>] prepare_creds+0x25/0x5e0 kernel/cred.c:258 [<000000002dabdc3e>] copy_creds+0x72/0x580 kernel/cred.c:358 [<00000000b42f49c9>] copy_process+0xfdc/0x7800 kernel/fork.c:2002 [<000000004f0a9922>] kernel_clone+0xe7/0x980 kernel/fork.c:2506 [<00000000426b75b9>] __do_sys_clone+0xc8/0x110 kernel/fork.c:2623 [<0000000077e2bfa7>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 [<00000000847b1208>] entry_SYSCALL_64_after_hwframe+0x62/0xc7 BUG: memory leak unreferenced object 0xffff88801b745140 (size 32): comm "syz-executor424", pid 261, jiffies 4294816223 (age 21.671s) hex dump (first 32 bytes): 01 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000c1e5dd6e>] kmalloc include/linux/slab.h:557 [inline] [<00000000c1e5dd6e>] kzalloc include/linux/slab.h:664 [inline] [<00000000c1e5dd6e>] lsm_cred_alloc security/security.c:536 [inline] [<00000000c1e5dd6e>] security_prepare_creds+0x112/0x190 security/security.c:1649 [<000000009752b638>] prepare_creds+0x452/0x5e0 kernel/cred.c:285 [<000000002dabdc3e>] copy_creds+0x72/0x580 kernel/cred.c:358 [<00000000b42f49c9>] copy_process+0xfdc/0x7800 kernel/fork.c:2002 [<000000004f0a9922>] kernel_clone+0xe7/0x980 kernel/fork.c:2506 [<00000000426b75b9>] __do_sys_clone+0xc8/0x110 kernel/fork.c:2623 [<0000000077e2bfa7>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 [<00000000847b1208>] entry_SYSCALL_64_after_hwframe+0x62/0xc7 BUG: memory leak unreferenced object 0xffff88800cb27680 (size 488): comm "syz-executor424", pid 262, jiffies 4294816227 (age 21.668s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ a0 d0 a3 08 80 88 ff ff 00 e0 54 0b 80 88 ff ff ..........T..... backtrace: [<00000000ab54c34c>] kmem_cache_zalloc include/linux/slab.h:654 [inline] [<00000000ab54c34c>] __alloc_file+0x21/0x320 fs/file_table.c:101 [<00000000ed739247>] alloc_empty_file+0x6d/0x170 fs/file_table.c:151 [<000000003b4d6ab6>] path_openat+0xe3/0x26e0 fs/namei.c:3417 [<00000000ad5e2d19>] do_filp_open+0x190/0x3e0 fs/namei.c:3458 [<00000000c8228c51>] do_sys_openat2+0x171/0x420 fs/open.c:1186 [<0000000071291ec6>] do_sys_open fs/open.c:1202 [inline] [<0000000071291ec6>] __do_sys_openat fs/open.c:1218 [inline] [<0000000071291ec6>] __se_sys_openat fs/open.c:1213 [inline] [<0000000071291ec6>] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1213 [<0000000077e2bfa7>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 [<00000000847b1208>] entry_SYSCALL_64_after_hwframe+0x62/0xc7 BUG: memory leak unreferenced object 0xffff88800eeb53e0 (size 16): comm "syz-executor424", pid 262, jiffies 4294816227 (age 21.668s) hex dump (first 16 bytes): 01 00 00 00 01 00 00 00 1b 00 00 00 01 00 00 00 ................ backtrace: [<00000000443731f5>] kmem_cache_zalloc include/linux/slab.h:654 [inline] [<00000000443731f5>] lsm_file_alloc security/security.c:571 [inline] [<00000000443731f5>] security_file_alloc+0x34/0x170 security/security.c:1472 [<000000009646dd81>] __alloc_file+0xb7/0x320 fs/file_table.c:106 [<00000000ed739247>] alloc_empty_file+0x6d/0x170 fs/file_table.c:151 [<000000003b4d6ab6>] path_openat+0xe3/0x26e0 fs/namei.c:3417 [<00000000ad5e2d19>] do_filp_open+0x190/0x3e0 fs/namei.c:3458 [<00000000c8228c51>] do_sys_openat2+0x171/0x420 fs/open.c:1186 [<0000000071291ec6>] do_sys_open fs/open.c:1202 [inline] [<0000000071291ec6>] __do_sys_openat fs/open.c:1218 [inline] [<0000000071291ec6>] __se_sys_openat fs/open.c:1213 [inline] [<0000000071291ec6>] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1213 [<0000000077e2bfa7>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 [<00000000847b1208>] entry_SYSCALL_64_after_hwframe+0x62/0xc7 BUG: memory leak unreferenced object 0xffff888008dc1a00 (size 168): comm "syz-executor424", pid 261, jiffies 4294824138 (age 13.757s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<0000000091ae1494>] prepare_creds+0x25/0x5e0 kernel/cred.c:258 [<000000002dabdc3e>] copy_creds+0x72/0x580 kernel/cred.c:358 [<00000000b42f49c9>] copy_process+0xfdc/0x7800 kernel/fork.c:2002 [<000000004f0a9922>] kernel_clone+0xe7/0x980 kernel/fork.c:2506 [<00000000426b75b9>] __do_sys_clone+0xc8/0x110 kernel/fork.c:2623 [<0000000077e2bfa7>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 [<00000000847b1208>] entry_SYSCALL_64_after_hwframe+0x62/0xc7 Syzkaller reproducer: # {Threaded:false Collide:false Repeat:true RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: Leak:true NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:false UseTmpDir:false HandleSegv:false Repro:false Trace:false LegacyOptions:{Fault:false FaultCall:0 FaultNth:0}} r0 = syz_io_uring_setup(0x21, &(0x7f0000000180)={0x0, 0xffffffff, 0x0, 0x3}, &(0x7f0000ffb000/0x3000)=nil, &(0x7f0000ffb000/0x4000)=nil, &(0x7f0000000000), &(0x7f0000002a40)) io_uring_register$IORING_REGISTER_FILES(r0, 0x2, &(0x7f0000001900)=[0xffffffffffffffff], 0x1) r1 = openat$full(0xffffffffffffff9c, &(0x7f0000000100), 0x0, 0x0) io_uring_register$IORING_REGISTER_FILES_UPDATE(r0, 0x6, &(0x7f0000000700)={0x0, 0x0, &(0x7f00000006c0)=[r1]}, 0x1) C reproducer: // autogenerated by syzkaller (https://github.com/google/syzkaller) #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include 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; } #define SIZEOF_IO_URING_SQE 64 #define SIZEOF_IO_URING_CQE 16 #define SQ_HEAD_OFFSET 0 #define SQ_TAIL_OFFSET 64 #define SQ_RING_MASK_OFFSET 256 #define SQ_RING_ENTRIES_OFFSET 264 #define SQ_FLAGS_OFFSET 276 #define SQ_DROPPED_OFFSET 272 #define CQ_HEAD_OFFSET 128 #define CQ_TAIL_OFFSET 192 #define CQ_RING_MASK_OFFSET 260 #define CQ_RING_ENTRIES_OFFSET 268 #define CQ_RING_OVERFLOW_OFFSET 284 #define CQ_FLAGS_OFFSET 280 #define CQ_CQES_OFFSET 320 struct io_sqring_offsets { uint32_t head; uint32_t tail; uint32_t ring_mask; uint32_t ring_entries; uint32_t flags; uint32_t dropped; uint32_t array; uint32_t resv1; uint64_t resv2; }; struct io_cqring_offsets { uint32_t head; uint32_t tail; uint32_t ring_mask; uint32_t ring_entries; uint32_t overflow; uint32_t cqes; uint64_t resv[2]; }; struct io_uring_params { uint32_t sq_entries; uint32_t cq_entries; uint32_t flags; uint32_t sq_thread_cpu; uint32_t sq_thread_idle; uint32_t features; uint32_t resv[4]; struct io_sqring_offsets sq_off; struct io_cqring_offsets cq_off; }; #define IORING_OFF_SQ_RING 0 #define IORING_OFF_SQES 0x10000000ULL #define sys_io_uring_setup 425 static long syz_io_uring_setup(volatile long a0, volatile long a1, volatile long a2, volatile long a3, volatile long a4, volatile long a5) { uint32_t entries = (uint32_t)a0; struct io_uring_params* setup_params = (struct io_uring_params*)a1; void* vma1 = (void*)a2; void* vma2 = (void*)a3; void** ring_ptr_out = (void**)a4; void** sqes_ptr_out = (void**)a5; uint32_t fd_io_uring = syscall(sys_io_uring_setup, entries, setup_params); uint32_t sq_ring_sz = setup_params->sq_off.array + setup_params->sq_entries * sizeof(uint32_t); uint32_t cq_ring_sz = setup_params->cq_off.cqes + setup_params->cq_entries * SIZEOF_IO_URING_CQE; uint32_t ring_sz = sq_ring_sz > cq_ring_sz ? sq_ring_sz : cq_ring_sz; *ring_ptr_out = mmap(vma1, ring_sz, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE | MAP_FIXED, fd_io_uring, IORING_OFF_SQ_RING); uint32_t sqes_sz = setup_params->sq_entries * SIZEOF_IO_URING_SQE; *sqes_ptr_out = mmap(vma2, sqes_sz, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE | MAP_FIXED, fd_io_uring, IORING_OFF_SQES); return fd_io_uring; } 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 KMEMLEAK_FILE "/sys/kernel/debug/kmemleak" static void setup_leak() { if (!write_file(KMEMLEAK_FILE, "scan")) exit(1); sleep(5); if (!write_file(KMEMLEAK_FILE, "scan")) exit(1); if (!write_file(KMEMLEAK_FILE, "clear")) exit(1); } static void check_leaks(void) { int fd = open(KMEMLEAK_FILE, O_RDWR); if (fd == -1) exit(1); uint64_t start = current_time_ms(); if (write(fd, "scan", 4) != 4) exit(1); sleep(1); while (current_time_ms() - start < 4 * 1000) sleep(1); if (write(fd, "scan", 4) != 4) exit(1); static char buf[128 << 10]; ssize_t n = read(fd, buf, sizeof(buf) - 1); if (n < 0) exit(1); int nleaks = 0; if (n != 0) { sleep(1); if (write(fd, "scan", 4) != 4) exit(1); if (lseek(fd, 0, SEEK_SET) < 0) exit(1); n = read(fd, buf, sizeof(buf) - 1); if (n < 0) exit(1); buf[n] = 0; char* pos = buf; char* end = buf + n; while (pos < end) { char* next = strstr(pos + 1, "unreferenced object"); if (!next) next = end; char prev = *next; *next = 0; fprintf(stderr, "BUG: memory leak\n%s\n", pos); *next = prev; pos = next; nleaks++; } } if (write(fd, "clear", 5) != 5) exit(1); close(fd); if (nleaks) exit(1); } 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; } check_leaks(); } } #ifndef __NR_io_uring_register #define __NR_io_uring_register 427 #endif uint64_t r[2] = {0xffffffffffffffff, 0xffffffffffffffff}; void execute_one(void) { intptr_t res = 0; *(uint32_t*)0x20000184 = -1; *(uint32_t*)0x20000188 = 0; *(uint32_t*)0x2000018c = 3; *(uint32_t*)0x20000190 = 0; *(uint32_t*)0x20000198 = -1; memset((void*)0x2000019c, 0, 12); res = -1; res = syz_io_uring_setup(0x21, 0x20000180, 0x20ffb000, 0x20ffb000, 0x20000000, 0x20002a40); if (res != -1) r[0] = res; *(uint32_t*)0x20001900 = -1; syscall(__NR_io_uring_register, r[0], 2ul, 0x20001900ul, 1ul); memcpy((void*)0x20000100, "/dev/full\000", 10); res = syscall(__NR_openat, 0xffffffffffffff9cul, 0x20000100ul, 0ul, 0ul); if (res != -1) r[1] = res; *(uint32_t*)0x20000700 = 0; *(uint32_t*)0x20000704 = 0; *(uint64_t*)0x20000708 = 0x200006c0; *(uint32_t*)0x200006c0 = r[1]; syscall(__NR_io_uring_register, r[0], 6ul, 0x20000700ul, 1ul); } 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); setup_leak(); loop(); return 0; }