From e27168f8c337b12b8aa8d59c3123c79d2f83603d Mon Sep 17 00:00:00 2001 From: Christof Schmitt Date: Thu, 17 Sep 2009 09:10:14 +0200 Subject: [PATCH] [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 Cc: stable@kernel.org Signed-off-by: Christof Schmitt Acked-by: Douglas Gilbert Signed-off-by: James Bottomley --- drivers/scsi/sg.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 0cb049f5cc56..a328b5f284de 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -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;