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scsi: sg: recheck MMAP_IO request length with lock held

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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>
This commit is contained in:
Todd Poynor 2017-08-15 21:48:43 -07:00 • committed by Greg Kroah-Hartman
parent 0d7592a03b
commit a2e71dcfb0
1 changed files with 5 additions and 2 deletions
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7
drivers/scsi/sg.c
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@ -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) {