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    SubjectRe: [PATCH] st: don't doublefree pages from scatterlist
    Hugh Dickins wrote:
    > On some architectures, mapping the scatterlist may coalesce entries:
    > if that coalesced list is then used for freeing the pages afterwards,
    > there's a danger that pages may be doubly freed (and others leaked).
    > Fix SCSI Tape's sgl_unmap_user_pages by freeing from the pagelist used
    > in sgl_map_user_pages. Fixes Ryan Richter's crash on x86_64, with Bad
    > page state mapcount 2 from sgl_unmap_user_pages, and consequent mayhem.

    Is this crash occuring with 2.6.16-rc1? I ask becuase in that kernel the
    scatterlist passed into scsi_execute_async

    if (scsi_execute_async(STp->device, cmd, direction,
    &((STp->buffer)->sg[0]), bytes,

    is not the same one that gets send down to the device/HBA.

    scsi_execute_async takes the scatterlist passed to it from st or sg,
    uses it as a hint to build a request + bios, then later when the request
    is sent to the device a new scatterlist is sent to the device and the
    device does the pci/dma operation on that scatterlist from the
    block/scsi layer.
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      Last update: 2006-02-03 21:40    [W:0.022 / U:9.060 seconds]
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