3.16.85-rc1 review patch. If anyone has any objections, please let me know.
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From: Todd Poynor toddpoynor@google.com
commit 8d26f491116feaa0b16de370b6a7ba40a40fa0b4 upstream.
Commit 1bc0eb044615 ("scsi: sg: protect accesses to 'reserved' page array") adds needed concurrency protection for the "reserve" buffer. Some checks that are initially made outside the lock are replicated once the lock is taken to ensure the checks and resulting decisions are made using consistent state.
The check that a request with flag SG_FLAG_MMAP_IO set fits in the reserve buffer also needs to be performed again under the lock to ensure the reserve buffer length compared against matches the value in effect when the request is linked to the reserve buffer. An -ENOMEM should be returned in this case, instead of switching over to an indirect buffer as for non-MMAP_IO requests.
Signed-off-by: Todd Poynor toddpoynor@google.com Acked-by: Douglas Gilbert dgilbert@interlog.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/scsi/sg.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1772,9 +1772,12 @@ sg_start_req(Sg_request *srp, unsigned c !sfp->res_in_use) { sfp->res_in_use = 1; sg_link_reserve(sfp, srp, dxfer_len); - } else if ((hp->flags & SG_FLAG_MMAP_IO) && sfp->res_in_use) { + } else if (hp->flags & SG_FLAG_MMAP_IO) { + res = -EBUSY; /* sfp->res_in_use == 1 */ + if (dxfer_len > rsv_schp->bufflen) + res = -ENOMEM; mutex_unlock(&sfp->f_mutex); - return -EBUSY; + return res; } else { res = sg_build_indirect(req_schp, sfp, dxfer_len); if (res) {