Hello I found a bug in io_uring and comfirmed at the latest upstream mainine linux. TITLE: KMSAN: uninit-value in io_rw_fail and I find this bug maybe existed in the https://syzkaller.appspot.com/bug?extid=12dde80bf174ac8ae285 but do not have a stable reproducer. However, I generate a stable reproducer and comfirmed in the latest mainline. If you fix this issue, please add the following tag to the commit: Reported-by: xingwei lee <xrivendell7@xxxxxxxxx> kernel: mainline a4aebe936554dac6a91e5d091179c934f8325708 kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=4a65fa9f077ead01 with KMSAN enabled compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 =* repro.c =* #define _GNU_SOURCE #include <dirent.h> #include <endian.h> #include <errno.h> #include <fcntl.h> #include <signal.h> #include <stdarg.h> #include <stdbool.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.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> #ifndef __NR_io_uring_enter #define __NR_io_uring_enter 426 #endif #ifndef __NR_io_uring_setup #define __NR_io_uring_setup 425 #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; } #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 static long syz_io_uring_setup(volatile long a0, volatile long a1, volatile long a2, volatile long a3) { uint32_t entries = (uint32_t)a0; struct io_uring_params* setup_params = (struct io_uring_params*)a1; void** ring_ptr_out = (void**)a2; void** sqes_ptr_out = (void**)a3; uint32_t fd_io_uring = syscall(__NR_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(0, ring_sz, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, fd_io_uring, IORING_OFF_SQ_RING); uint32_t sqes_sz = setup_params->sq_entries * SIZEOF_IO_URING_SQE; *sqes_ptr_out = mmap(0, sqes_sz, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, fd_io_uring, IORING_OFF_SQES); uint32_t* array = (uint32_t*)((uintptr_t)*ring_ptr_out + setup_params->sq_off.array); for (uint32_t index = 0; index < entries; index++) array[index] = index; return fd_io_uring; } static long syz_io_uring_submit(volatile long a0, volatile long a1, volatile long a2) { char* ring_ptr = (char*)a0; char* sqes_ptr = (char*)a1; char* sqe = (char*)a2; uint32_t sq_ring_mask = *(uint32_t*)(ring_ptr + SQ_RING_MASK_OFFSET); uint32_t* sq_tail_ptr = (uint32_t*)(ring_ptr + SQ_TAIL_OFFSET); uint32_t sq_tail = *sq_tail_ptr & sq_ring_mask; char* sqe_dest = sqes_ptr + sq_tail * SIZEOF_IO_URING_SQE; memcpy(sqe_dest, sqe, SIZEOF_IO_URING_SQE); uint32_t sq_tail_next = *sq_tail_ptr + 1; __atomic_store_n(sq_tail_ptr, sq_tail_next, __ATOMIC_RELEASE); return 0; } 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[3] = {0xffffffffffffffff, 0x0, 0x0}; void execute_one(void) { intptr_t res = 0; *(uint32_t*)0x200001c4 = 0; *(uint32_t*)0x200001c8 = 0x10100; *(uint32_t*)0x200001cc = 0; *(uint32_t*)0x200001d0 = 0; *(uint32_t*)0x200001d8 = -1; memset((void*)0x200001dc, 0, 12); res = -1; res = syz_io_uring_setup(/*entries=*/0x24f7, /*params=*/0x200001c0, /*ring_ptr=*/0x20000040, /*sqes_ptr=*/0x20000100); if (res != -1) { r[0] = res; r[1] = *(uint64_t*)0x20000040; r[2] = *(uint64_t*)0x20000100; } *(uint8_t*)0x20000740 = 2; *(uint8_t*)0x20000741 = 0x10; *(uint16_t*)0x20000742 = 0; *(uint32_t*)0x20000744 = 0; *(uint64_t*)0x20000748 = 0; *(uint64_t*)0x20000750 = 0; *(uint32_t*)0x20000758 = 0xfffffe08; *(uint32_t*)0x2000075c = 0; *(uint64_t*)0x20000760 = 0; *(uint16_t*)0x20000768 = 0; *(uint16_t*)0x2000076a = 0; memset((void*)0x2000076c, 0, 20); syz_io_uring_submit(/*ring_ptr=*/r[1], /*sqes_ptr=*/r[2], /*sqe=*/0x20000740); syscall(__NR_io_uring_enter, /*fd=*/r[0], /*to_submit=*/0x2d3e, /*min_complete=*/0, /*flags=*/0ul, /*sigmask=*/0ul, /*size=*/0ul); } int main(void) { syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul); syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, /*prot=*/7ul, /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul); syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul); loop(); return 0; } =* repro.txt =* r0 = syz_io_uring_setup(0x24f7, &(0x7f00000001c0)={0x0, 0x0, 0x10100}, &(0x7f0000000040)=<r1=>0x0, &(0x7f0000000100)=<r2=>0x0) syz_io_uring_submit(r1, r2, &(0x7f0000000740)=@IORING_OP_WRITEV={0x2, 0x10, 0x0, @fd_index, 0x0, 0x0, 0xfffffffffffffe08}) io_uring_enter(r0, 0x2d3e, 0x0, 0x0, 0x0, 0x0) Please also see: https://gist.github.com/xrivendell7/0adf878b11e3a71676e1dc696e1c9398 I hope it helps. Thanks! Best regards. xingwei Lee
