The SCSI generic driver is currently broken in the 3.18, 4.1, 4.4, and 4.9 stable kernels.  This is the problematic commit:

109bade9c625 ("scsi: sg: use standard lists for sg_requests")

(all commit ids are from upstream git, not stable.git)

There have already been a number of fixes backported to -stable to fix problems introduced by that commit:

bd46fc406b30 ("scsi: sg: off by one in sg_ioctl()") 4759df905a47 ("scsi: sg: factor out sg_fill_request_table()") 3e0097499839 ("scsi: sg: fixup infoleak when using SG_GET_REQUEST_TABLE") 587c3c9f286c ("scsi: sg: Re-fix off by one in sg_fill_request_table()")

I am not sure why 109bade9c625 was added to -stable to begin with.  My guess is that the "infoleak" fix was flagged as being appropriate for -stable, and it depended on the original commit 109bade9c625.  But if you take a close look, the original commit 109bade9c625 is what introduced the infoleak in the first place.  Or maybe there was some other reason.  But I digress.

There is one more fix for 109bade9c625 that has not yet been backported:

48ae8484e9fc ("scsi: sg: don't return bogus Sg_requests")

Without the fix above, sg oopses as soon as I try to use it.  So please add 48ae8484e9fc to -stable.

The following -stable kernels already have 48ae8484e9fc: 4.14.31 4.15.14

The following -stable kernels need 48ae8484e9fc: 3.18.102 4.1.51 4.4.125 4.9.91

The following -stable kernels are not affected because they have not had the problematic commit backported: 3.2.101 3.16.56

Related bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=198081

Thanks! Tony Battersby Cybernetics