Hello, I reproduced this bug in the upstream linux. If you fix this issue, please add the following tag to the commit: Reported-by: xingwei lee <xrivendell7@xxxxxxxxx> Notice: I use the same config with syzbot dashboard. kernel version: c1ca10ceffbb289ed02feaf005bc9ee6095b4507 kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=e3dd779fba027968 with KASAN enabled compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 ===================================================== BUG: KMSAN: uninit-value in bpf_bprintf_prepare+0x22f1/0x2950 kernel/bpf/helpers.c:934 bpf_bprintf_prepare+0x22f1/0x2950 kernel/bpf/helpers.c:934 ____bpf_snprintf kernel/bpf/helpers.c:1060 [inline] bpf_snprintf+0x15e/0x3a0 kernel/bpf/helpers.c:1044 ___bpf_prog_run+0x232b/0xe6a0 kernel/bpf/core.c:1986 __bpf_prog_run288+0xc0/0xf0 kernel/bpf/core.c:2226 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline] __bpf_prog_run include/linux/filter.h:651 [inline] bpf_prog_run include/linux/filter.h:658 [inline] bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline] bpf_flow_dissect+0x13c/0x490 net/core/flow_dissector.c:991 bpf_prog_test_run_flow_dissector+0x78c/0xad0 net/bpf/test_run.c:1359 bpf_prog_test_run+0x74c/0xb90 kernel/bpf/syscall.c:4107 __sys_bpf+0x73b/0xfe0 kernel/bpf/syscall.c:5475 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline] __se_sys_bpf kernel/bpf/syscall.c:5559 [inline] __x64_sys_bpf+0xa9/0xf0 kernel/bpf/syscall.c:5559 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b Local variable stack created at: __bpf_prog_run288+0x50/0xf0 kernel/bpf/core.c:2226 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline] __bpf_prog_run include/linux/filter.h:651 [inline] bpf_prog_run include/linux/filter.h:658 [inline] bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline] bpf_flow_dissect+0x13c/0x490 net/core/flow_dissector.c:991 CPU: 2 PID: 11419 Comm: syz-executor.3 Not tainted 6.8.0-rc4-00331-gc1ca10ceffbb-dirty #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 ===================================================== =* 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/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_bpf #define __NR_bpf 321 #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"); } 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[4] = {0xffffffffffffffff, 0xffffffffffffffff, 0xffffffffffffffff, 0xffffffffffffffff}; void execute_one(void) { intptr_t res = 0; *(uint32_t*)0x20000340 = 2; *(uint32_t*)0x20000344 = 4; *(uint32_t*)0x20000348 = 8; *(uint32_t*)0x2000034c = 1; *(uint32_t*)0x20000350 = 0x80; *(uint32_t*)0x20000354 = 0; *(uint32_t*)0x20000358 = 0; memset((void*)0x2000035c, 0, 16); *(uint32_t*)0x2000036c = 0; *(uint32_t*)0x20000370 = -1; *(uint32_t*)0x20000374 = 0; *(uint32_t*)0x20000378 = 0; *(uint32_t*)0x2000037c = 0; *(uint64_t*)0x20000380 = 0; res = syscall(__NR_bpf, /*cmd=*/0ul, /*arg=*/0x20000340ul, /*size=*/0x48ul); if (res != -1) r[0] = res; *(uint32_t*)0x20000180 = r[0]; *(uint64_t*)0x20000188 = 0x20000100; *(uint32_t*)0x20000100 = 0; *(uint64_t*)0x20000190 = 0x20000140; memcpy((void*)0x20000140, "%pi6 \000", 8); *(uint64_t*)0x20000198 = 0; res = syscall(__NR_bpf, /*cmd=*/2ul, /*arg=*/0x20000180ul, /*size=*/0x20ul); if (res != -1) r[1] = *(uint32_t*)0x20000180; *(uint32_t*)0x200000c0 = r[1]; res = syscall(__NR_bpf, /*cmd=*/0x16ul, /*arg=*/0x200000c0ul, /*size=*/4ul); if (res != -1) r[2] = *(uint32_t*)0x200000c0; *(uint32_t*)0x200004c0 = 0x16; *(uint32_t*)0x200004c4 = 0x10; *(uint64_t*)0x200004c8 = 0x20000040; memcpy((void*)0x20000040, "\x18\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xb7" "\x08\x00\x00\x00\x00\x00\x00\x7b\x8a\xf8\xff\x00\x00\x00\x00\xb7\x08" "\x00\x00\xff\xff\x0b\x86\x7b\x8a\xf0\xff\x00\x00\x00\x00\xbf\xa1\x00" "\x00\x00\x00\x00\x00\x07\x01\x00\x00\xf8\xff\xff\xff\xbf\xa4\x00\x00" "\x00\x00\x00\x00\x07\x04\x00\x00\xf0\xfe\xff\xff\xb7\x02\x00\x00\x08" "\x00\x00\x00\x18\x23\x00\x00", 92); *(uint32_t*)0x2000009c = r[2]; memcpy((void*)0x200000a0, "\x00\x00\x00\x00\x00\x00\x00\x00\xb7\x05\x00\x00\x08\x00\x00\x00\x85" "\x00\x00\x00\xa5\x00\x00\x00\x95", 25); *(uint64_t*)0x200004d0 = 0x20000600; memcpy((void*)0x20000600, "GPL\000", 4); *(uint32_t*)0x200004d8 = 0; *(uint32_t*)0x200004dc = 0; *(uint64_t*)0x200004e0 = 0; *(uint32_t*)0x200004e8 = 0; *(uint32_t*)0x200004ec = 0; memset((void*)0x200004f0, 0, 16); *(uint32_t*)0x20000500 = 0; *(uint32_t*)0x20000504 = 0; *(uint32_t*)0x20000508 = 0; *(uint32_t*)0x2000050c = 0; *(uint64_t*)0x20000510 = 0; *(uint32_t*)0x20000518 = 0; *(uint32_t*)0x2000051c = 0; *(uint64_t*)0x20000520 = 0; *(uint32_t*)0x20000528 = 0; *(uint32_t*)0x2000052c = 0; *(uint32_t*)0x20000530 = 0; *(uint32_t*)0x20000534 = 0; *(uint64_t*)0x20000538 = 0; *(uint64_t*)0x20000540 = 0; *(uint32_t*)0x20000548 = 0; *(uint32_t*)0x2000054c = 0; res = syscall(__NR_bpf, /*cmd=*/5ul, /*arg=*/0x200004c0ul, /*size=*/0x90ul); if (res != -1) r[3] = res; *(uint32_t*)0x20000640 = r[3]; *(uint32_t*)0x20000644 = 0; *(uint32_t*)0x20000648 = 0xe; *(uint32_t*)0x2000064c = 0; *(uint64_t*)0x20000650 = 0x20000000; memcpy((void*)0x20000000, "\x40\xf0\x53\x8e\xf0\x47\xb2\x1f\xb6\x00\x68\x30\x55\x00", 14); *(uint64_t*)0x20000658 = 0; *(uint32_t*)0x20000660 = 0; *(uint32_t*)0x20000664 = 0; *(uint32_t*)0x20000668 = 0; *(uint32_t*)0x2000066c = 0; *(uint64_t*)0x20000670 = 0; *(uint64_t*)0x20000678 = 0; *(uint32_t*)0x20000680 = 0; *(uint32_t*)0x20000684 = 0; *(uint32_t*)0x20000688 = 0; syscall(__NR_bpf, /*cmd=*/0xaul, /*arg=*/0x20000640ul, /*size=*/0x50ul); } 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; } Remember to run this repro.txt with the command: syz-execprog -repeat 0 ./repro.txt. =* repro.txt =* r0 = bpf$MAP_CREATE_CONST_STR(0x0, &(0x7f0000000340)={0x2, 0x4, 0x8, 0x1, 0x80, 0x0}, 0x48) bpf$MAP_UPDATE_CONST_STR(0x2, &(0x7f0000000180)={{r0, <r1=>0xffffffffffffffff}, &(0x7f0000000100), &(0x7f0000000140)='%pi6 \x00'}, 0x20) bpf$BPF_MAP_CONST_STR_FREEZE(0x16, &(0x7f00000000c0)={r1, <r2=>0xffffffffffffffff}, 0x4) r3 = bpf$PROG_LOAD(0x5, &(0x7f00000004c0)={0x16, 0x10, &(0x7f0000000040)=ANY=[@ANYBLOB="18000000000000000000000000000000b7080000000000007b8af8ff00000000b7080000ffff0b867b8af0ff00000000bfa100000000000007010000f8ffffffbfa400000000000007040000f0feffffb70200000800000018230000", @ANYRES32=r2, @ANYBLOB="0000000000000000b70500000800000085000000a500000095"], &(0x7f0000000600)='GPL\x00', 0x0, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, 0x90) bpf$BPF_PROG_TEST_RUN(0xa, &(0x7f0000000640)={r3, 0x0, 0xe, 0x0, &(0x7f0000000000)="40f0538ef047b21fb60068305500", 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, 0x50) and see also in https://gist.github.com/xrivendell7/707f897c1d4c261a33a877c047ae3b1e. BTW, this bug maybe similar to this one KMSAN: uninit-value in bstr_printf(https://syzkaller.appspot.com/bug?extid=f0d29b273acdcd3a2562) I hope it helps. Best regards! xingwei Lee
