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authorTodd Poynor <toddpoynor@google.com>2017-08-15 21:48:43 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-13 14:09:45 -0700
commita2e71dcfb0d47748ba8d947db52e4dafc019c6dc (patch)
tree84fd034a5d0c5e2b442219b2676a433af2d08e1c
parent0d7592a03b8abd032afa19aed99ab89dec7f394a (diff)
downloadlinux-linaro-stable-a2e71dcfb0d47748ba8d947db52e4dafc019c6dc.tar.gz
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>
-rw-r--r--drivers/scsi/sg.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index fc1d9d33873f..71325972e503 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1757,9 +1757,12 @@ 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) {