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    Subject[PATCH 4.14 317/323] block: reexpand iov_iter after read/write
    Date
    From: yangerkun <yangerkun@huawei.com>

    [ Upstream commit cf7b39a0cbf6bf57aa07a008d46cf695add05b4c ]

    We get a bug:

    BUG: KASAN: slab-out-of-bounds in iov_iter_revert+0x11c/0x404
    lib/iov_iter.c:1139
    Read of size 8 at addr ffff0000d3fb11f8 by task

    CPU: 0 PID: 12582 Comm: syz-executor.2 Not tainted
    5.10.0-00843-g352c8610ccd2 #2
    Hardware name: linux,dummy-virt (DT)
    Call trace:
    dump_backtrace+0x0/0x2d0 arch/arm64/kernel/stacktrace.c:132
    show_stack+0x28/0x34 arch/arm64/kernel/stacktrace.c:196
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0x110/0x164 lib/dump_stack.c:118
    print_address_description+0x78/0x5c8 mm/kasan/report.c:385
    __kasan_report mm/kasan/report.c:545 [inline]
    kasan_report+0x148/0x1e4 mm/kasan/report.c:562
    check_memory_region_inline mm/kasan/generic.c:183 [inline]
    __asan_load8+0xb4/0xbc mm/kasan/generic.c:252
    iov_iter_revert+0x11c/0x404 lib/iov_iter.c:1139
    io_read fs/io_uring.c:3421 [inline]
    io_issue_sqe+0x2344/0x2d64 fs/io_uring.c:5943
    __io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260
    io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326
    io_submit_sqe fs/io_uring.c:6395 [inline]
    io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624
    __do_sys_io_uring_enter fs/io_uring.c:9013 [inline]
    __se_sys_io_uring_enter fs/io_uring.c:8960 [inline]
    __arm64_sys_io_uring_enter+0x190/0x708 fs/io_uring.c:8960
    __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
    invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
    el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
    do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:227
    el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
    el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
    el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670

    Allocated by task 12570:
    stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
    kasan_save_stack mm/kasan/common.c:48 [inline]
    kasan_set_track mm/kasan/common.c:56 [inline]
    __kasan_kmalloc+0xdc/0x120 mm/kasan/common.c:461
    kasan_kmalloc+0xc/0x14 mm/kasan/common.c:475
    __kmalloc+0x23c/0x334 mm/slub.c:3970
    kmalloc include/linux/slab.h:557 [inline]
    __io_alloc_async_data+0x68/0x9c fs/io_uring.c:3210
    io_setup_async_rw fs/io_uring.c:3229 [inline]
    io_read fs/io_uring.c:3436 [inline]
    io_issue_sqe+0x2954/0x2d64 fs/io_uring.c:5943
    __io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260
    io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326
    io_submit_sqe fs/io_uring.c:6395 [inline]
    io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624
    __do_sys_io_uring_enter fs/io_uring.c:9013 [inline]
    __se_sys_io_uring_enter fs/io_uring.c:8960 [inline]
    __arm64_sys_io_uring_enter+0x190/0x708 fs/io_uring.c:8960
    __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
    invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
    el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
    do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:227
    el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
    el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
    el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670

    Freed by task 12570:
    stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
    kasan_save_stack mm/kasan/common.c:48 [inline]
    kasan_set_track+0x38/0x6c mm/kasan/common.c:56
    kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:355
    __kasan_slab_free+0x124/0x150 mm/kasan/common.c:422
    kasan_slab_free+0x10/0x1c mm/kasan/common.c:431
    slab_free_hook mm/slub.c:1544 [inline]
    slab_free_freelist_hook mm/slub.c:1577 [inline]
    slab_free mm/slub.c:3142 [inline]
    kfree+0x104/0x38c mm/slub.c:4124
    io_dismantle_req fs/io_uring.c:1855 [inline]
    __io_free_req+0x70/0x254 fs/io_uring.c:1867
    io_put_req_find_next fs/io_uring.c:2173 [inline]
    __io_queue_sqe+0x1fc/0x520 fs/io_uring.c:6279
    __io_req_task_submit+0x154/0x21c fs/io_uring.c:2051
    io_req_task_submit+0x2c/0x44 fs/io_uring.c:2063
    task_work_run+0xdc/0x128 kernel/task_work.c:151
    get_signal+0x6f8/0x980 kernel/signal.c:2562
    do_signal+0x108/0x3a4 arch/arm64/kernel/signal.c:658
    do_notify_resume+0xbc/0x25c arch/arm64/kernel/signal.c:722
    work_pending+0xc/0x180

    blkdev_read_iter can truncate iov_iter's count since the count + pos may
    exceed the size of the blkdev. This will confuse io_read that we have
    consume the iovec. And once we do the iov_iter_revert in io_read, we
    will trigger the slab-out-of-bounds. Fix it by reexpand the count with
    size has been truncated.

    blkdev_write_iter can trigger the problem too.

    Signed-off-by: yangerkun <yangerkun@huawei.com>
    Acked-by: Pavel Begunkov <asml.silencec@gmail.com>
    Link: https://lore.kernel.org/r/20210401071807.3328235-1-yangerkun@huawei.com
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/block_dev.c | 20 +++++++++++++++++---
    1 file changed, 17 insertions(+), 3 deletions(-)

    diff --git a/fs/block_dev.c b/fs/block_dev.c
    index 23fb999b49e1..a56974d04010 100644
    --- a/fs/block_dev.c
    +++ b/fs/block_dev.c
    @@ -1906,6 +1906,7 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
    struct inode *bd_inode = bdev_file_inode(file);
    loff_t size = i_size_read(bd_inode);
    struct blk_plug plug;
    + size_t shorted = 0;
    ssize_t ret;

    if (bdev_read_only(I_BDEV(bd_inode)))
    @@ -1920,12 +1921,17 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
    if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
    return -EOPNOTSUPP;

    - iov_iter_truncate(from, size - iocb->ki_pos);
    + size -= iocb->ki_pos;
    + if (iov_iter_count(from) > size) {
    + shorted = iov_iter_count(from) - size;
    + iov_iter_truncate(from, size);
    + }

    blk_start_plug(&plug);
    ret = __generic_file_write_iter(iocb, from);
    if (ret > 0)
    ret = generic_write_sync(iocb, ret);
    + iov_iter_reexpand(from, iov_iter_count(from) + shorted);
    blk_finish_plug(&plug);
    return ret;
    }
    @@ -1937,13 +1943,21 @@ ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
    struct inode *bd_inode = bdev_file_inode(file);
    loff_t size = i_size_read(bd_inode);
    loff_t pos = iocb->ki_pos;
    + size_t shorted = 0;
    + ssize_t ret;

    if (pos >= size)
    return 0;

    size -= pos;
    - iov_iter_truncate(to, size);
    - return generic_file_read_iter(iocb, to);
    + if (iov_iter_count(to) > size) {
    + shorted = iov_iter_count(to) - size;
    + iov_iter_truncate(to, size);
    + }
    +
    + ret = generic_file_read_iter(iocb, to);
    + iov_iter_reexpand(to, iov_iter_count(to) + shorted);
    + return ret;
    }
    EXPORT_SYMBOL_GPL(blkdev_read_iter);

    --
    2.30.2


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