From 9189c03e1f513985d7a3171ef10a4b16afb8f394 Mon Sep 17 00:00:00 2001 From: Todd Poynor Date: Tue, 15 Aug 2017 21:48:43 -0700 Subject: [PATCH] scsi: sg: recheck MMAP_IO request length with lock held BugLink: http://bugs.launchpad.net/bugs/1716284 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 Acked-by: Douglas Gilbert Signed-off-by: Martin K. Petersen Signed-off-by: Greg Kroah-Hartman Signed-off-by: Seth Forshee --- drivers/scsi/sg.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index dfe4a11666a7..aad6ebb51735 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1741,9 +1741,12 @@ sg_start_req(Sg_request *srp, unsigned char *cmd) !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) { -- 2.39.2