Re: [syzbot] [bpf?] KMSAN: uninit-value in __bpf_strtoull

From: xingwei lee
Date: Thu Mar 21 2024 - 02:41:53 EST

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In reply to: syzbot: "[syzbot] [bpf?] KMSAN: uninit-value in __bpf_strtoull"
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Hello, I reproduced this bug and comfired in the latest net tree.

If you fix this issue, please add the following tag to the commit:
Reported-by: xingwei lee <xrivendell7@xxxxxxxxx>
Reported-by: yue sun <samsun1006219@xxxxxxxxx>

kernel version: net.git 32fa4366cc4da1c97b725a0066adf43c6b298f37
kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=5c1d7ee7e74661a8
with KMSAN enabled
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

root@syzkaller:~# ./6be
=====================================================
BUG: KMSAN: uninit-value in __bpf_strtoull+0x292/0x690 kernel/bpf/helpers.c:465
__bpf_strtoull+0x292/0x690 kernel/bpf/helpers.c:465
__bpf_strtoll kernel/bpf/helpers.c:504 [inline]
____bpf_strtol kernel/bpf/helpers.c:525 [inline]
bpf_strtol+0x87/0x2c0 kernel/bpf/helpers.c:519
___bpf_prog_run+0x14de/0xec60 kernel/bpf/core.c:1997
__bpf_prog_run96+0xc0/0xf0 kernel/bpf/core.c:2236
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run_xdp include/net/xdp.h:514 [inline]
bpf_test_run+0x464/0xcc0 net/bpf/test_run.c:423
bpf_prog_test_run_xdp+0x101c/0x1c70 net/bpf/test_run.c:1269
bpf_prog_test_run+0x754/0xba0 kernel/bpf/syscall.c:4240
__sys_bpf+0x7a6/0x1010 kernel/bpf/syscall.c:5649
__do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
__x64_sys_bpf+0xa9/0xf0 kernel/bpf/syscall.c:5736
do_syscall_64+0xd5/0x1f0
entry_SYSCALL_64_after_hwframe+0x6d/0x75
Local variable stack created at:
__bpf_prog_run96+0x50/0xf0 kernel/bpf/core.c:2236
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run_xdp include/net/xdp.h:514 [inline]
bpf_test_run+0x464/0xcc0 net/bpf/test_run.c:423
CPU: 2 PID: 8031 Comm: 6be Not tainted 6.8.0-05242-g32fa4366cc4d #3
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[2] = {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 = 0;
*(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*)0x200004c0 = 6;
*(uint32_t*)0x200004c4 = 0x10;
*(uint64_t*)0x200004c8 = 0x20000000;
memcpy((void*)0x20000000,
"\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\xb8\xff\x00\x00\x00\x00\xb7\x08"
"\x00\x00\x00\x00\x00\x00\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\xff\xff\xff\xb7\x02\x00\x00\x08"
"\x00\x00\x00\x18\x23\x00\x00",
92);
*(uint32_t*)0x2000005c = r[0];
memcpy((void*)0x20000060,
"\x00\x00\x00\x00\x00\x00\x00\x00\xb7\x03\x00\x00\x00\x00\x00\x00\x85"
"\x00\x00\x00\x69\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[1] = res;
*(uint32_t*)0x20000640 = r[1];
*(uint32_t*)0x20000644 = 5;
*(uint32_t*)0x20000648 = 0;
*(uint32_t*)0x2000064c = 0;
*(uint64_t*)0x20000650 = 0;
*(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=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);
loop();
return 0;
}

=* repro.txt =*
r0 = bpf$MAP_CREATE_CONST_STR(0x0, &(0x7f0000000340)={0x2, 0x4, 0x8,
0x1, 0x80, 0x0, 0x0, '\x00', 0x0, 0x0}, 0x48)
r1 = bpf$PROG_LOAD(0x5, &(0x7f00000004c0)={0x6, 0x10,
&(0x7f0000000000)=ANY=[@ANYBLOB="18000000000000000000000000000000b7080000000000007b8ab8ff00000000b7080000000000007b8af0ff00000000bfa100000000000007010000f8ffffffbfa400000000000007040000f0ffffffb70200000800000018230000",
@ANYRES32=r0, @ANYBLOB="0000000000000000b703000000000000850000006900000095"],
&(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)={r1, 0x5, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, 0x50)

and see also in
https://gist.github.com/xrivendell7/37b74ecaeccd48127ed6137127a6b134

I hope it helps.
Best regards
xingwei Lee

Next message: Fei Shao: "[PATCH 2/2] spi: spi-mt65xx: Rename a variable in interrupt handler"
Previous message: Adrian Hunter: "Re: [PATCH v7 0/2] mmc: sdhci-of-dwcmshc: Add CQE support"
In reply to: syzbot: "[syzbot] [bpf?] KMSAN: uninit-value in __bpf_strtoull"
Next in thread: Alexei Starovoitov: "Re: [syzbot] [bpf?] KMSAN: uninit-value in __bpf_strtoull"
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