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    Subject[PATCH 041/241] target: Avoid integer overflow in se_dev_align_max_sectors()
    Date
    3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Roland Dreier <roland@purestorage.com>

    commit 3e03989b5868acf69a391a424dc71fcd6cc48167 upstream.

    The expression (max_sectors * block_size) might overflow a u32
    (indeed, since iblock sets max_hw_sectors to UINT_MAX, it is
    guaranteed to overflow and end up with a much-too-small result in many
    common cases). Fix this by doing an equivalent calculation that
    doesn't require multiplication.

    While we're touching this code, avoid splitting a printk format across
    two lines and use pr_info(...) instead of printk(KERN_INFO ...).

    Signed-off-by: Roland Dreier <roland@purestorage.com>
    Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
    [ herton: unfuzz patch ]
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    drivers/target/target_core_device.c | 18 +++++++++---------
    1 file changed, 9 insertions(+), 9 deletions(-)

    diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
    index 5ad9728..8542099 100644
    --- a/drivers/target/target_core_device.c
    +++ b/drivers/target/target_core_device.c
    @@ -824,20 +824,20 @@ int se_dev_check_shutdown(struct se_device *dev)

    u32 se_dev_align_max_sectors(u32 max_sectors, u32 block_size)
    {
    - u32 tmp, aligned_max_sectors;
    + u32 aligned_max_sectors;
    + u32 alignment;
    /*
    * Limit max_sectors to a PAGE_SIZE aligned value for modern
    * transport_allocate_data_tasks() operation.
    */
    - tmp = rounddown((max_sectors * block_size), PAGE_SIZE);
    - aligned_max_sectors = (tmp / block_size);
    - if (max_sectors != aligned_max_sectors) {
    - printk(KERN_INFO "Rounding down aligned max_sectors from %u"
    - " to %u\n", max_sectors, aligned_max_sectors);
    - return aligned_max_sectors;
    - }
    + alignment = max(1ul, PAGE_SIZE / block_size);
    + aligned_max_sectors = rounddown(max_sectors, alignment);
    +
    + if (max_sectors != aligned_max_sectors)
    + pr_info("Rounding down aligned max_sectors from %u to %u\n",
    + max_sectors, aligned_max_sectors);

    - return max_sectors;
    + return aligned_max_sectors;
    }

    void se_dev_set_default_attribs(
    --
    1.7.9.5


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