342b3360ae
commit 310ca162d779efee8a2dc3731439680f3e9c1e86 upstream. syzbot is reporting NULL pointer dereference [1] which is caused by race condition between ioctl(loop_fd, LOOP_CLR_FD, 0) versus ioctl(other_loop_fd, LOOP_SET_FD, loop_fd) due to traversing other loop devices at loop_validate_file() without holding corresponding lo->lo_ctl_mutex locks. Since ioctl() request on loop devices is not frequent operation, we don't need fine grained locking. Let's use global lock in order to allow safe traversal at loop_validate_file(). Note that syzbot is also reporting circular locking dependency between bdev->bd_mutex and lo->lo_ctl_mutex [2] which is caused by calling blkdev_reread_part() with lock held. This patch does not address it. [1] https://syzkaller.appspot.com/bug?id=f3cfe26e785d85f9ee259f385515291d21bd80a3 [2] https://syzkaller.appspot.com/bug?id=bf154052f0eea4bc7712499e4569505907d15889 Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: syzbot <syzbot+bf89c128e05dd6c62523@syzkaller.appspotmail.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
94 lines
2.3 KiB
C
94 lines
2.3 KiB
C
/*
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* loop.h
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*
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* Written by Theodore Ts'o, 3/29/93.
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*
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* Copyright 1993 by Theodore Ts'o. Redistribution of this file is
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* permitted under the GNU General Public License.
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*/
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#ifndef _LINUX_LOOP_H
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#define _LINUX_LOOP_H
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/blk-mq.h>
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#include <linux/spinlock.h>
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#include <linux/mutex.h>
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#include <linux/kthread.h>
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#include <uapi/linux/loop.h>
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/* Possible states of device */
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enum {
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Lo_unbound,
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Lo_bound,
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Lo_rundown,
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};
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struct loop_func_table;
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struct loop_device {
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int lo_number;
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atomic_t lo_refcnt;
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loff_t lo_offset;
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loff_t lo_sizelimit;
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int lo_flags;
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int (*transfer)(struct loop_device *, int cmd,
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struct page *raw_page, unsigned raw_off,
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struct page *loop_page, unsigned loop_off,
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int size, sector_t real_block);
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char lo_file_name[LO_NAME_SIZE];
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char lo_crypt_name[LO_NAME_SIZE];
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char lo_encrypt_key[LO_KEY_SIZE];
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int lo_encrypt_key_size;
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struct loop_func_table *lo_encryption;
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__u32 lo_init[2];
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kuid_t lo_key_owner; /* Who set the key */
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int (*ioctl)(struct loop_device *, int cmd,
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unsigned long arg);
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struct file * lo_backing_file;
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struct block_device *lo_device;
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void *key_data;
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gfp_t old_gfp_mask;
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spinlock_t lo_lock;
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int lo_state;
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struct kthread_worker worker;
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struct task_struct *worker_task;
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bool use_dio;
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bool sysfs_inited;
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struct request_queue *lo_queue;
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struct blk_mq_tag_set tag_set;
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struct gendisk *lo_disk;
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};
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struct loop_cmd {
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struct kthread_work work;
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bool use_aio; /* use AIO interface to handle I/O */
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atomic_t ref; /* only for aio */
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long ret;
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struct kiocb iocb;
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struct bio_vec *bvec;
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struct cgroup_subsys_state *css;
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};
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/* Support for loadable transfer modules */
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struct loop_func_table {
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int number; /* filter type */
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int (*transfer)(struct loop_device *lo, int cmd,
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struct page *raw_page, unsigned raw_off,
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struct page *loop_page, unsigned loop_off,
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int size, sector_t real_block);
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int (*init)(struct loop_device *, const struct loop_info64 *);
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/* release is called from loop_unregister_transfer or clr_fd */
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int (*release)(struct loop_device *);
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int (*ioctl)(struct loop_device *, int cmd, unsigned long arg);
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struct module *owner;
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};
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int loop_register_transfer(struct loop_func_table *funcs);
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int loop_unregister_transfer(int number);
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#endif
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