| Description: | In sg_io, blk_rq_map_user{,_iov} may allocate a set of bounce buffer pages to do the bio, if it finds the user buffer cannot be directly mapped. But the allocated pages are not cleared. If the bounce buffer is also not written to by device, garbage data is left, and copied back to user in blk_rq_unmap_user. The allocated pages should be cleared. This also eliminates the risk of leaking sensitive information to userspace, which may have a security impact.
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