block/loop: fix race between I/O and set_status
Inside set_status, transfer need to setup again, so we have to drain IO before the transition, otherwise oops may be triggered like the following: divide error: 0000 [#1] SMP KASAN CPU: 0 PID: 2935 Comm: loop7 Not tainted 4.10.0-rc7+ #213 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff88006ba1e840 task.stack: ffff880067338000 RIP: 0010:transfer_xor+0x1d1/0x440 drivers/block/loop.c:110 RSP: 0018:ffff88006733f108 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff8800688d7000 RCX: 0000000000000059 RDX: 0000000000000000 RSI: 1ffff1000d743f43 RDI: ffff880068891c08 RBP: ffff88006733f160 R08: ffff8800688d7001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800688d7000 R13: ffff880067b7d000 R14: dffffc0000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88006d000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000006c17e0 CR3: 0000000066e3b000 CR4: 00000000001406f0 Call Trace: lo_do_transfer drivers/block/loop.c:251 [inline] lo_read_transfer drivers/block/loop.c:392 [inline] do_req_filebacked drivers/block/loop.c:541 [inline] loop_handle_cmd drivers/block/loop.c:1677 [inline] loop_queue_work+0xda0/0x49b0 drivers/block/loop.c:1689 kthread_worker_fn+0x4c3/0xa30 kernel/kthread.c:630 kthread+0x326/0x3f0 kernel/kthread.c:227 ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430 Code: 03 83 e2 07 41 29 df 42 0f b6 04 30 4d 8d 44 24 01 38 d0 7f 08 84 c0 0f 85 62 02 00 00 44 89 f8 41 0f b6 48 ff 25 ff 01 00 00 99 <f7> 7d c8 48 63 d2 48 03 55 d0 48 89 d0 48 89 d7 48 c1 e8 03 83 RIP: transfer_xor+0x1d1/0x440 drivers/block/loop.c:110 RSP: ffff88006733f108 ---[ end trace 0166f7bd3b0c0933 ]--- Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: stable@vger.kernel.org Signed-off-by: Ming Lei <tom.leiming@gmail.com> Tested-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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605cdf0875
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ecdd09597a
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@ -1097,9 +1097,12 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
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if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
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return -EINVAL;
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/* I/O need to be drained during transfer transition */
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blk_mq_freeze_queue(lo->lo_queue);
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err = loop_release_xfer(lo);
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if (err)
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return err;
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goto exit;
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if (info->lo_encrypt_type) {
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unsigned int type = info->lo_encrypt_type;
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@ -1114,12 +1117,14 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
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err = loop_init_xfer(lo, xfer, info);
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if (err)
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return err;
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goto exit;
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if (lo->lo_offset != info->lo_offset ||
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lo->lo_sizelimit != info->lo_sizelimit)
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if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit))
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return -EFBIG;
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if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) {
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err = -EFBIG;
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goto exit;
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}
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loop_config_discard(lo);
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@ -1156,7 +1161,9 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
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/* update dio if lo_offset or transfer is changed */
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__loop_update_dio(lo, lo->use_dio);
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return 0;
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exit:
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blk_mq_unfreeze_queue(lo->lo_queue);
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return err;
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}
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static int
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