Commit e27168f8 authored Sep 17, 2009 by Christof Schmitt Committed by James Bottomley Oct 02, 2009

[SCSI] sg: Free data buffers after calling blk_rq_unmap_user



Running sg_luns on s390x with CONFIG_DEBUG_PAGEALLOC enabled fails
with EFAULT from the SG_IO ioctl. The EFAULT is the result from
copy_to_user failing in this call chain:

sg_ioctl
sg_new_read
sg_finish_rem_req
blk_rq_unmap_user
__blk_rq_unmap_user
bio_uncopy_user
__bio_copy_iov
copy_to_user

The sg driver calls sg_remove_scat to free the memory pages before
calling blk_rq_unmap_user that tries to copy the data back to
userspace. Change the order to first call blk_rq_unmap_user before
freeing the pages in sg_remove_scat.

Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: stable@kernel.org
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

parent 5915136d

drivers/scsi/sg.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -1708,11 +1708,6 @@ static int sg_finish_rem_req(Sg_request * srp)
		Sg_scatter_hold *req_schp = &srp->data;

		SCSI_LOG_TIMEOUT(4, printk("sg_finish_rem_req: res_used=%d\n", (int) srp->res_used));
		if (srp->res_used)
		sg_unlink_reserve(sfp, srp);
		else
		sg_remove_scat(req_schp);

		if (srp->rq) {
		if (srp->bio)
		ret = blk_rq_unmap_user(srp->bio);
		@@ -1720,6 +1715,11 @@ static int sg_finish_rem_req(Sg_request * srp)
		blk_put_request(srp->rq);
		}

		if (srp->res_used)
		sg_unlink_reserve(sfp, srp);
		else
		sg_remove_scat(req_schp);

		sg_remove_request(sfp, srp);

		return ret;

Admin message