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    Subject[PATCH 5.15 017/917] char: xillybus: fix msg_ep UAF in xillyusb_probe()
    Date
    From: Ziyang Xuan <william.xuanziyang@huawei.com>

    commit 15c9a359094ec6251578b02387436bc64f11a477 upstream.

    When endpoint_alloc() return failed in xillyusb_setup_base_eps(),
    'xdev->msg_ep' will be freed but not set to NULL. That lets program
    enter fail handling to cleanup_dev() in xillyusb_probe(). Check for
    'xdev->msg_ep' is invalid in cleanup_dev() because 'xdev->msg_ep' did
    not set to NULL when was freed. So the UAF problem for 'xdev->msg_ep'
    is triggered.

    ==================================================================
    BUG: KASAN: use-after-free in fifo_mem_release+0x1f4/0x210
    CPU: 0 PID: 166 Comm: kworker/0:2 Not tainted 5.15.0-rc5+ #19
    Call Trace:
    dump_stack_lvl+0xe2/0x152
    print_address_description.constprop.0+0x21/0x140
    ? fifo_mem_release+0x1f4/0x210
    kasan_report.cold+0x7f/0x11b
    ? xillyusb_probe+0x530/0x700
    ? fifo_mem_release+0x1f4/0x210
    fifo_mem_release+0x1f4/0x210
    ? __sanitizer_cov_trace_pc+0x1d/0x50
    endpoint_dealloc+0x35/0x2b0
    cleanup_dev+0x90/0x120
    xillyusb_probe+0x59a/0x700
    ...

    Freed by task 166:
    kasan_save_stack+0x1b/0x40
    kasan_set_track+0x1c/0x30
    kasan_set_free_info+0x20/0x30
    __kasan_slab_free+0x109/0x140
    kfree+0x117/0x4c0
    xillyusb_probe+0x606/0x700

    Set 'xdev->msg_ep' to NULL after being freed in xillyusb_setup_base_eps()
    to fix the UAF problem.

    Fixes: a53d1202aef1 ("char: xillybus: Add driver for XillyUSB (Xillybus variant for USB)")
    Cc: stable <stable@vger.kernel.org>
    Acked-by: Eli Billauer <eli.billauer@gmail.com>
    Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
    Link: https://lore.kernel.org/r/20211016052047.1611983-1-william.xuanziyang@huawei.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/char/xillybus/xillyusb.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/drivers/char/xillybus/xillyusb.c
    +++ b/drivers/char/xillybus/xillyusb.c
    @@ -1912,6 +1912,7 @@ static int xillyusb_setup_base_eps(struc

    dealloc:
    endpoint_dealloc(xdev->msg_ep); /* Also frees FIFO mem if allocated */
    + xdev->msg_ep = NULL;
    return -ENOMEM;
    }


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