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    Subject[PATCH 5.10 102/104] net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()
    Date
    From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>

    commit 2a80c15812372e554474b1dba0b1d8e467af295d upstream.

    syzbot found WARNING in qrtr_tun_write_iter [1] when write_iter length
    exceeds KMALLOC_MAX_SIZE causing order >= MAX_ORDER condition.

    Additionally, there is no check for 0 length write.

    [1]
    WARNING: mm/page_alloc.c:5011
    [..]
    Call Trace:
    alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
    alloc_pages include/linux/gfp.h:547 [inline]
    kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
    kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
    kmalloc include/linux/slab.h:557 [inline]
    kzalloc include/linux/slab.h:682 [inline]
    qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
    call_write_iter include/linux/fs.h:1901 [inline]

    Reported-by: syzbot+c2a7e5c5211605a90865@syzkaller.appspotmail.com
    Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
    Link: https://lore.kernel.org/r/20210202092059.1361381-1-snovitoll@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/qrtr/tun.c | 6 ++++++
    1 file changed, 6 insertions(+)

    --- a/net/qrtr/tun.c
    +++ b/net/qrtr/tun.c
    @@ -80,6 +80,12 @@ static ssize_t qrtr_tun_write_iter(struc
    ssize_t ret;
    void *kbuf;

    + if (!len)
    + return -EINVAL;
    +
    + if (len > KMALLOC_MAX_SIZE)
    + return -ENOMEM;
    +
    kbuf = kzalloc(len, GFP_KERNEL);
    if (!kbuf)
    return -ENOMEM;

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