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    Subject[PATCH 4.9 15/31] asm-generic: sections: refactor memory_intersects
    Date
    From: Quanyang Wang <quanyang.wang@windriver.com>

    commit 0c7d7cc2b4fe2e74ef8728f030f0f1674f9f6aee upstream.

    There are two problems with the current code of memory_intersects:

    First, it doesn't check whether the region (begin, end) falls inside the
    region (virt, vend), that is (virt < begin && vend > end).

    The second problem is if vend is equal to begin, it will return true but
    this is wrong since vend (virt + size) is not the last address of the
    memory region but (virt + size -1) is. The wrong determination will
    trigger the misreporting when the function check_for_illegal_area calls
    memory_intersects to check if the dma region intersects with stext region.

    The misreporting is as below (stext is at 0x80100000):
    WARNING: CPU: 0 PID: 77 at kernel/dma/debug.c:1073 check_for_illegal_area+0x130/0x168
    DMA-API: chipidea-usb2 e0002000.usb: device driver maps memory from kernel text or rodata [addr=800f0000] [len=65536]
    Modules linked in:
    CPU: 1 PID: 77 Comm: usb-storage Not tainted 5.19.0-yocto-standard #5
    Hardware name: Xilinx Zynq Platform
    unwind_backtrace from show_stack+0x18/0x1c
    show_stack from dump_stack_lvl+0x58/0x70
    dump_stack_lvl from __warn+0xb0/0x198
    __warn from warn_slowpath_fmt+0x80/0xb4
    warn_slowpath_fmt from check_for_illegal_area+0x130/0x168
    check_for_illegal_area from debug_dma_map_sg+0x94/0x368
    debug_dma_map_sg from __dma_map_sg_attrs+0x114/0x128
    __dma_map_sg_attrs from dma_map_sg_attrs+0x18/0x24
    dma_map_sg_attrs from usb_hcd_map_urb_for_dma+0x250/0x3b4
    usb_hcd_map_urb_for_dma from usb_hcd_submit_urb+0x194/0x214
    usb_hcd_submit_urb from usb_sg_wait+0xa4/0x118
    usb_sg_wait from usb_stor_bulk_transfer_sglist+0xa0/0xec
    usb_stor_bulk_transfer_sglist from usb_stor_bulk_srb+0x38/0x70
    usb_stor_bulk_srb from usb_stor_Bulk_transport+0x150/0x360
    usb_stor_Bulk_transport from usb_stor_invoke_transport+0x38/0x440
    usb_stor_invoke_transport from usb_stor_control_thread+0x1e0/0x238
    usb_stor_control_thread from kthread+0xf8/0x104
    kthread from ret_from_fork+0x14/0x2c

    Refactor memory_intersects to fix the two problems above.

    Before the 1d7db834a027e ("dma-debug: use memory_intersects()
    directly"), memory_intersects is called only by printk_late_init:

    printk_late_init -> init_section_intersects ->memory_intersects.

    There were few places where memory_intersects was called.

    When commit 1d7db834a027e ("dma-debug: use memory_intersects()
    directly") was merged and CONFIG_DMA_API_DEBUG is enabled, the DMA
    subsystem uses it to check for an illegal area and the calltrace above
    is triggered.

    [akpm@linux-foundation.org: fix nearby comment typo]
    Link: https://lkml.kernel.org/r/20220819081145.948016-1-quanyang.wang@windriver.com
    Fixes: 979559362516 ("asm/sections: add helpers to check for section data")
    Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
    Cc: Ard Biesheuvel <ardb@kernel.org>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Thierry Reding <treding@nvidia.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    include/asm-generic/sections.h | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- a/include/asm-generic/sections.h
    +++ b/include/asm-generic/sections.h
    @@ -87,7 +87,7 @@ static inline bool memory_contains(void
    /**
    * memory_intersects - checks if the region occupied by an object intersects
    * with another memory region
    - * @begin: virtual address of the beginning of the memory regien
    + * @begin: virtual address of the beginning of the memory region
    * @end: virtual address of the end of the memory region
    * @virt: virtual address of the memory object
    * @size: size of the memory object
    @@ -100,7 +100,10 @@ static inline bool memory_intersects(voi
    {
    void *vend = virt + size;

    - return (virt >= begin && virt < end) || (vend >= begin && vend < end);
    + if (virt < end && vend > begin)
    + return true;
    +
    + return false;
    }

    /**

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