From: Christof Schmitt <christof.schmitt@xxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx
Signed-off-by: Christof Schmitt <christof.schmitt@xxxxxxxxxx>
---
drivers/scsi/sg.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
--- a/drivers/scsi/sg.c 2009-09-15 18:18:11.000000000 +0200
+++ b/drivers/scsi/sg.c 2009-09-15 18:18:45.000000000 +0200
@@ -1708,11 +1708,6 @@ static int sg_finish_rem_req(Sg_request
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
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;
--
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