Hi,
I've got the following error report while fuzzing the kernel with syzkaller.
A reproducer is attached.
You may need to run it a few times.
On commit 9c763584b7c8911106bb77af7e648bef09af9d80 (4.9-rc6, Nov 20).
==================================================================
BUG: KASAN: use-after-free in bcm_rx_thr_flush+0x284/0x2b0
Read of size 1 at addr ffff88006c1faae5 by task a.out/3874
page:ffffea0001b07e80 count:1 mapcount:0 mapping: (null) index:0x0
flags: 0x100000000000080(slab)
page dumped because: kasan: bad access detected
CPU: 1 PID: 3874 Comm: a.out Not tainted 4.9.0-rc6+ #427
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
ffff88006ab07900 ffffffff81b472e4 ffff88006ab07990 ffff88006c1faae5
00000000000000fa 00000000000000fb ffff88006ab07980 ffffffff8150ad42
ffff88006323ce58 0000000000000246 ffff880068ca8000 0000000000000282
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff81b472e4>] dump_stack+0xb3/0x10f lib/dump_stack.c:51
[< inline >] describe_address mm/kasan/report.c:259
[<ffffffff8150ad42>] kasan_report_error+0x122/0x560 mm/kasan/report.c:365
[< inline >] kasan_report mm/kasan/report.c:387
[<ffffffff8150b1be>] __asan_report_load1_noabort+0x3e/0x40
mm/kasan/report.c:405
[< inline >] bcm_rx_do_flush net/can/bcm.c:589
[<ffffffff83577e04>] bcm_rx_thr_flush+0x284/0x2b0 net/can/bcm.c:612
[< inline >] bcm_rx_setup net/can/bcm.c:1199
[<ffffffff83578b36>] bcm_sendmsg+0xbb6/0x30e0 net/can/bcm.c:1351
[< inline >] sock_sendmsg_nosec net/socket.c:621
[<ffffffff82b7176c>] sock_sendmsg+0xcc/0x110 net/socket.c:631
[<ffffffff82b73651>] ___sys_sendmsg+0x771/0x8b0 net/socket.c:1954
[<ffffffff82b7563e>] __sys_sendmsg+0xce/0x170 net/socket.c:1988
[< inline >] SYSC_sendmsg net/socket.c:1999
[<ffffffff82b7570d>] SyS_sendmsg+0x2d/0x50 net/socket.c:1995
[<ffffffff83fc4301>] entry_SYSCALL_64_fastpath+0x1f/0xc2
arch/x86/entry/entry_64.S:209
The buggy address belongs to the object at ffff88006c1faae0
which belongs to the cache kmalloc-32 of size 32
The buggy address ffff88006c1faae5 is located 5 bytes inside
of 32-byte region [ffff88006c1faae0, ffff88006c1fab00)
Freed by task 2013:
[<ffffffff8107e236>] save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
[<ffffffff81509e56>] save_stack+0x46/0xd0 mm/kasan/kasan.c:495
[< inline >] set_track mm/kasan/kasan.c:507
[<ffffffff8150a6b3>] kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:571
[< inline >] slab_free_hook mm/slub.c:1352
[< inline >] slab_free_freelist_hook mm/slub.c:1374
[< inline >] slab_free mm/slub.c:2951
[<ffffffff81506b98>] kfree+0xe8/0x2b0 mm/slub.c:3871
[<ffffffff819dd8c1>] selinux_cred_free+0x51/0x80 security/selinux/hooks.c:3725
[<ffffffff819ce358>] security_cred_free+0x48/0x80 security/security.c:907
[<ffffffff8117e27d>] put_cred_rcu+0xed/0x390 kernel/cred.c:116
[< inline >] __rcu_reclaim kernel/rcu/rcu.h:118
[< inline >] rcu_do_batch kernel/rcu/tree.c:2776
[< inline >] invoke_rcu_callbacks kernel/rcu/tree.c:3040
[< inline >] __rcu_process_callbacks kernel/rcu/tree.c:3007
[<ffffffff8125dfe0>] rcu_process_callbacks+0xa40/0x1190 kernel/rcu/tree.c:3024
[<ffffffff83fc70af>] __do_softirq+0x23f/0x8e5 kernel/softirq.c:284
Allocated by task 1826:
[<ffffffff8107e236>] save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
[<ffffffff81509e56>] save_stack+0x46/0xd0 mm/kasan/kasan.c:495
[< inline >] set_track mm/kasan/kasan.c:507
[<ffffffff8150a0cb>] kasan_kmalloc+0xab/0xe0 mm/kasan/kasan.c:598
[<ffffffff8150a632>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:537
[< inline >] slab_post_alloc_hook mm/slab.h:417
[< inline >] slab_alloc_node mm/slub.c:2708
[< inline >] slab_alloc mm/slub.c:2716
[<ffffffff815090ef>] __kmalloc_track_caller+0xcf/0x2a0 mm/slub.c:4240
[<ffffffff8146bf84>] kmemdup+0x24/0x50 mm/util.c:113
[<ffffffff819dcbe9>] selinux_cred_prepare+0x49/0xb0
security/selinux/hooks.c:3739
[<ffffffff819ce40d>] security_prepare_creds+0x7d/0xb0 security/security.c:912
[<ffffffff8117fab3>] prepare_creds+0x243/0x340 kernel/cred.c:277
[<ffffffff81181bab>] copy_creds+0x7b/0x5c0 kernel/cred.c:343
[<ffffffff81109c6e>] copy_process.part.45+0x86e/0x5b50 kernel/fork.c:1529
[< inline >] copy_process kernel/fork.c:1479
[<ffffffff8110f2fa>] _do_fork+0x1ba/0xcc0 kernel/fork.c:1933
[< inline >] SYSC_clone kernel/fork.c:2043
[<ffffffff8110fed7>] SyS_clone+0x37/0x50 kernel/fork.c:2037
[<ffffffff81006465>] do_syscall_64+0x195/0x490 arch/x86/entry/common.c:280
[<ffffffff83fc43c9>] return_from_SYSCALL_64+0x0/0x7a
arch/x86/entry/entry_64.S:251
Memory state around the buggy address:
ffff88006c1fa980: fc fc fb fb fb fb fc fc fb fb fb fb fc fc fb fb
ffff88006c1faa00: fb fb fc fc fb fb fb fb fc fc fb fb fb fb fc fc
>ffff88006c1faa80: fb fb fb fb fc fc fb fb fb fb fc fc fb fb fb fb
^
ffff88006c1fab00: fc fc fb fb fb fb fc fc 00 00 00 00 fc fc 00 00
ffff88006c1fab80: 00 00 fc fc fb fb fb fb fc fc fb fb fb fb fc fc
==================================================================
Thanks!
// autogenerated by syzkaller (http://github.com/google/syzkaller)
#ifndef __NR_socket
#define __NR_socket 41
#endif
#ifndef __NR_syz_fuse_mount
#define __NR_syz_fuse_mount 1000004
#endif
#ifndef __NR_syz_fuseblk_mount
#define __NR_syz_fuseblk_mount 1000005
#endif
#ifndef __NR_syz_open_pts
#define __NR_syz_open_pts 1000003
#endif
#ifndef __NR_syz_test
#define __NR_syz_test 1000001
#endif
#ifndef __NR_mmap
#define __NR_mmap 9
#endif
#ifndef __NR_connect
#define __NR_connect 42
#endif
#ifndef __NR_sendmsg
#define __NR_sendmsg 46
#endif
#ifndef __NR_syz_open_dev
#define __NR_syz_open_dev 1000002
#endif
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <net/if_arp.h>
#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <pthread.h>
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
__thread int skip_segv;
__thread jmp_buf segv_env;
static void segv_handler(int sig, siginfo_t* info, void* uctx)
{
if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED))
_longjmp(segv_env, 1);
exit(sig);
}
static void install_segv_handler()
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = segv_handler;
sa.sa_flags = SA_NODEFER | SA_SIGINFO;
sigaction(SIGSEGV, &sa, NULL);
sigaction(SIGBUS, &sa, NULL);
}
#define NONFAILING(...) \
{ \
__atomic_fetch_add(&skip_segv, 1, __ATOMIC_SEQ_CST); \
if (_setjmp(segv_env) == 0) { \
__VA_ARGS__; \
} \
__atomic_fetch_sub(&skip_segv, 1, __ATOMIC_SEQ_CST); \
}
static uintptr_t syz_open_dev(uintptr_t a0, uintptr_t a1, uintptr_t 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));
buf[sizeof(buf) - 1] = 0;
while ((hash = strchr(buf, '#'))) {
*hash = '0' + (char)(a1 % 10);
a1 /= 10;
}
return open(buf, a2, 0);
}
}
static uintptr_t syz_open_pts(uintptr_t a0, uintptr_t a1)
{
int ptyno = 0;
if (ioctl(a0, TIOCGPTN, &ptyno))
return -1;
char buf[128];
sprintf(buf, "/dev/pts/%d", ptyno);
return open(buf, a1, 0);
}
static uintptr_t syz_fuse_mount(uintptr_t a0, uintptr_t a1,
uintptr_t a2, uintptr_t a3,
uintptr_t a4, uintptr_t a5)
{
uint64_t target = a0;
uint64_t mode = a1;
uint64_t uid = a2;
uint64_t gid = a3;
uint64_t maxread = a4;
uint64_t flags = a5;
int fd = open("/dev/fuse", O_RDWR);
if (fd == -1)
return fd;
char buf[1024];
sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd,
(long)uid, (long)gid, (unsigned)mode & ~3u);
if (maxread != 0)
sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread);
if (mode & 1)
strcat(buf, ",default_permissions");
if (mode & 2)
strcat(buf, ",allow_other");
syscall(SYS_mount, "", target, "fuse", flags, buf);
return fd;
}
static uintptr_t syz_fuseblk_mount(uintptr_t a0, uintptr_t a1,
uintptr_t a2, uintptr_t a3,
uintptr_t a4, uintptr_t a5,
uintptr_t a6, uintptr_t a7)
{
uint64_t target = a0;
uint64_t blkdev = a1;
uint64_t mode = a2;
uint64_t uid = a3;
uint64_t gid = a4;
uint64_t maxread = a5;
uint64_t blksize = a6;
uint64_t flags = a7;
int fd = open("/dev/fuse", O_RDWR);
if (fd == -1)
return fd;
if (syscall(SYS_mknodat, AT_FDCWD, blkdev, S_IFBLK, makedev(7, 199)))
return fd;
char buf[256];
sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd,
(long)uid, (long)gid, (unsigned)mode & ~3u);
if (maxread != 0)
sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread);
if (blksize != 0)
sprintf(buf + strlen(buf), ",blksize=%ld", (long)blksize);
if (mode & 1)
strcat(buf, ",default_permissions");
if (mode & 2)
strcat(buf, ",allow_other");
syscall(SYS_mount, blkdev, target, "fuseblk", flags, buf);
return fd;
}
static uintptr_t execute_syscall(int nr, uintptr_t a0, uintptr_t a1,
uintptr_t a2, uintptr_t a3,
uintptr_t a4, uintptr_t a5,
uintptr_t a6, uintptr_t a7,
uintptr_t a8)
{
switch (nr) {
default:
return syscall(nr, a0, a1, a2, a3, a4, a5);
case __NR_syz_test:
return 0;
case __NR_syz_open_dev:
return syz_open_dev(a0, a1, a2);
case __NR_syz_open_pts:
return syz_open_pts(a0, a1);
case __NR_syz_fuse_mount:
return syz_fuse_mount(a0, a1, a2, a3, a4, a5);
case __NR_syz_fuseblk_mount:
return syz_fuseblk_mount(a0, a1, a2, a3, a4, a5, a6, a7);
}
}
long r[25];
int main()
{
install_segv_handler();
memset(r, -1, sizeof(r));
r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0xf60000ul, 0x3ul,
0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0);
r[1] = execute_syscall(__NR_socket, 0x1dul, 0x80002ul, 0x2ul, 0, 0, 0,
0, 0, 0);
NONFAILING(*(uint16_t*)0x20f57000 = (uint16_t)0x27);
NONFAILING(*(uint32_t*)0x20f57004 = (uint32_t)0x0);
NONFAILING(*(uint32_t*)0x20f57008 = (uint32_t)0x0);
NONFAILING(*(uint32_t*)0x20f5700c = (uint32_t)0x0);
NONFAILING(*(uint8_t*)0x20f57010 = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f57011 = (uint8_t)0x0);
NONFAILING(memcpy(
(void*)0x20f57012,
"\x34\x1b\x3a\x01\xb2\x57\x84\x9c\xa1\xd7\xd1\xff\x9f\x99\x9d\x81"
"\x27\xb1\x85\xf8\x8d\x1d\x77\x5d\x59\xc8\x8a\x3a\xa6\xa8\xdd\xac"
"\xdf\x2b\xdc\x32\x4e\xa6\x57\x8a\x21\xb8\x51\x14\x61\x01\x86\xc3"
"\x81\x7c\x34\xb0\x5e\xaf\xfd\x2c\x3f\x54\xf5\x7f\xa8\x1b\xa0",
63));
NONFAILING(*(uint64_t*)0x20f57058 = (uint64_t)0x0);
r[10] = execute_syscall(__NR_connect, r[1], 0x20f57000ul, 0x60ul, 0,
0, 0, 0, 0, 0);
NONFAILING(*(uint64_t*)0x20b05000 = (uint64_t)0x20f55000);
NONFAILING(*(uint32_t*)0x20b05008 = (uint32_t)0x0);
NONFAILING(*(uint64_t*)0x20b05010 = (uint64_t)0x20008fe0);
NONFAILING(*(uint64_t*)0x20b05018 = (uint64_t)0x2);
NONFAILING(*(uint64_t*)0x20b05020 = (uint64_t)0x20f54000);
NONFAILING(*(uint64_t*)0x20b05028 = (uint64_t)0x0);
NONFAILING(*(uint32_t*)0x20b05030 = (uint32_t)0x0);
NONFAILING(*(uint64_t*)0x20008fe0 = (uint64_t)0x20d5fff1);
NONFAILING(*(uint64_t*)0x20008fe8 = (uint64_t)0xf);
NONFAILING(*(uint64_t*)0x20008ff0 = (uint64_t)0x20f55000);
NONFAILING(*(uint64_t*)0x20008ff8 = (uint64_t)0x69);
NONFAILING(memcpy(
(void*)0x20d5fff1,
"\x05\x00\x00\x00\x8d\x13\x00\x00\x00\x00\x17\x14\xb7\x7e\xa6",
15));
NONFAILING(memcpy(
(void*)0x20f55000,
"\x12\x6f\x39\xb6\x5b\x4e\xed\x90\x77\xe0\x54\xbf\xb6\xb2\x41\xd7"
"\x36\x5d\x58\xfa\xa8\x32\x7a\x6d\x25\x89\x01\x00\xdd\x00\xc5\x89"
"\x07\xec\xc2\x76\x8d\x02\x00\x00\x00\x10\xb4\x27\xab\x6c\x2a\x41"
"\xe2\x54\x47\xcc\x08\xca\x75\x2a\x03\x89\xd3\x04\x71\x3f\x75\x90"
"\xf4\xda\xc6\xd9\xa7\x50\xff\xe8\x3e\xff\xcd\x31\x1b\xa2\x0a\xee"
"\x8a\x72\x6b\xda\x74\x75\x92\xbf\xad\xf0\x71\xb9\xb7\x70\x04\xbb"
"\x58\x40\x7d\x50\x14\x6b\xd7\xc2\x60",
105));
r[24] = execute_syscall(__NR_sendmsg, r[1], 0x20b05000ul, 0x0ul, 0, 0,
0, 0, 0, 0);
return 0;
}
