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Tony Battersby authored
sg has the following problems related to device removal: * opening a sg fd races with removing a device * closing a sg fd races with removing a device * /proc/scsi/sg/* access races with removing a device * command completion races with removing a device * command completion races with closing a sg fd * can rmmod sg with active commands These problems can cause kernel oopses, memory-use-after-free, or double-free errors. This patch fixes these problems by using krefs to manage the lifetime of sg_device and sg_fd. Each command submitted to the midlevel holds a reference to sg_fd until the completion callback. This ensures that sg_fd doesn't go away if the fd is closed with commands still outstanding. sg_fd gets the reference of sg_device (with scsi_device) and also makes sure that the sg module doesn't go away. /proc/scsi/sg/* functions don't play nicely with krefs because they give information about sg_fds which have been closed but not yet freed due to still having outstanding commands and sg_devices which have been removed but not yet freed due to still being referenced by one or more sg_fds. To deal with this safely without removing functionality, /proc functions now access sg_device and sg_fd while holding a lock instead of using kref_get()/kref_put(). Signed-off-by:
Tony Battersby <tonyb@cybernetics.com> Acked-by:
Douglas Gilbert <dgilbert@interlog.com> Signed-off-by:
James Bottomley <James.Bottomley@HansenPartnership.com>
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