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    Subject[PATCH 3/11] ACPI: Fix acpi_os_read_memory() and acpi_os_write_memory()
    Date
    From: Rafael J. Wysocki <rjw@sisk.pl>

    The functions acpi_os_read_memory() and acpi_os_write_memory() do
    two wrong things. First, they shouldn't call rcu_read_unlock()
    before the looked up address is actually used for I/O, because in
    that case the mapping it belongs to may be removed before the I/O
    is done. Second, they shouldn't use the physical address if
    there's no mapping for it, because that may lead to problems (at
    least for the "write" case it's like sending data to a random
    physical address in the hope it's going to work).

    Make the rcu_read_unlock() be called by these functions when the I/O
    is complete and modify them to dump stack and return error code if
    the requested physical address is not present in the ACPI iomaps.

    Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
    ---
    drivers/acpi/osl.c | 31 +++++++++++++------------------
    1 file changed, 13 insertions(+), 18 deletions(-)

    Index: linux-2.6/drivers/acpi/osl.c
    ===================================================================
    --- linux-2.6.orig/drivers/acpi/osl.c
    +++ linux-2.6/drivers/acpi/osl.c
    @@ -638,17 +638,17 @@ acpi_os_read_memory(acpi_physical_addres
    {
    u32 dummy;
    void __iomem *virt_addr;
    - int size = width / 8, unmap = 0;
    +
    + if (!value)
    + value = &dummy;

    rcu_read_lock();
    - virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
    - rcu_read_unlock();
    + virt_addr = acpi_map_vaddr_lookup(phys_addr, width / 8);
    if (!virt_addr) {
    - virt_addr = acpi_os_ioremap(phys_addr, size);
    - unmap = 1;
    + rcu_read_unlock();
    + WARN(true, "Address not mapped: %llx\n", phys_addr);
    + return AE_BAD_ADDRESS;
    }
    - if (!value)
    - value = &dummy;

    switch (width) {
    case 8:
    @@ -663,9 +663,7 @@ acpi_os_read_memory(acpi_physical_addres
    default:
    BUG();
    }
    -
    - if (unmap)
    - iounmap(virt_addr);
    + rcu_read_unlock();

    return AE_OK;
    }
    @@ -674,14 +672,13 @@ acpi_status
    acpi_os_write_memory(acpi_physical_address phys_addr, u32 value, u32 width)
    {
    void __iomem *virt_addr;
    - int size = width / 8, unmap = 0;

    rcu_read_lock();
    - virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
    - rcu_read_unlock();
    + virt_addr = acpi_map_vaddr_lookup(phys_addr, width / 8);
    if (!virt_addr) {
    - virt_addr = acpi_os_ioremap(phys_addr, size);
    - unmap = 1;
    + rcu_read_unlock();
    + WARN(true, "Address not mapped: %llx\n", phys_addr);
    + return AE_BAD_ADDRESS;
    }

    switch (width) {
    @@ -697,9 +694,7 @@ acpi_os_write_memory(acpi_physical_addre
    default:
    BUG();
    }
    -
    - if (unmap)
    - iounmap(virt_addr);
    + rcu_read_unlock();

    return AE_OK;
    }


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