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authorTodd Poynor <toddpoynor@google.com>2017-08-15 21:48:43 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-09 17:39:42 +0200
commit7791b59153cb2adfe2fa4273b2f9c8925c3238ed (patch)
parentb06e1abf1ff26046f0f3369b7abe8a221dadf26b (diff)
scsi: sg: recheck MMAP_IO request length with lock held
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>
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0506a776cc10..9236a13d5d2a 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1747,9 +1747,12 @@ 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;
- return -EBUSY;
+ return res;
} else {
res = sg_build_indirect(req_schp, sfp, dxfer_len);
if (res) {