[PATCH v2 3/5] scsi: ufs: bsg: Validate request_len before accessing request

[Stanley Jhu <stanleyjhu@google.com>]

ufs_bsg_request() and ufs_bsg_exec_advanced_rpmb_req() read the
request buffer without checking job->request_len, which userspace
controls. A short request causes an out-of-bounds read. Found by
syzkaller.

Reject requests shorter than the structure each path reads.

Fixes: 64d4864714c2 ("scsi: ufs: bsg: Remove unnecessary length checkup")
Fixes: 6ff265fc5ef6 ("scsi: ufs: core: bsg: Add advanced RPMB support in ufs_bsg")
Cc: stable@vger.kernel.org
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Stanley Jhu <stanleyjhu@google.com>
---
Changes in v2:
- Complete the job on the early -EINVAL return through out_complete
  (added in patch 1). Kept Bean's Reviewed-by; Bean, please let me
  know if you would like to look again.

 drivers/ufs/core/ufs_bsg.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/ufs/core/ufs_bsg.c b/drivers/ufs/core/ufs_bsg.c
index 545ef7b79ceb..0db830e54ef0 100644
--- a/drivers/ufs/core/ufs_bsg.c
+++ b/drivers/ufs/core/ufs_bsg.c
@@ -73,6 +73,9 @@ static int ufs_bsg_exec_advanced_rpmb_req(struct ufs_hba *hba, struct bsg_job *j
 	if (hba->ufs_version < ufshci_version(4, 0) || !hba->dev_info.b_advanced_rpmb_en)
 		return -EINVAL;
 
+	if (job->request_len < sizeof(*rpmb_request))
+		return -EINVAL;
+
 	if (rpmb_request->ehs_req.length != 2 || rpmb_request->ehs_req.ehs_type != 1)
 		return -EINVAL;
 
@@ -142,6 +145,11 @@ static int ufs_bsg_request(struct bsg_job *job)
 
 	memset(job->reply, 0, job->reply_len);
 
+	if (job->request_len < sizeof(*bsg_request)) {
+		ret = -EINVAL;
+		goto out_complete;
+	}
+
 	ufshcd_rpm_get_sync(hba);
 
 	msgcode = bsg_request->msgcode;
@@ -194,6 +202,7 @@ static int ufs_bsg_request(struct bsg_job *job)
 out:
 	ufshcd_rpm_put_sync(hba);
 	kfree(buff);
+out_complete:
 	bsg_reply->result = ret;
 	if (ret == 0)
 		job->reply_len = rpmb ? sizeof(struct ufs_rpmb_reply) :
-- 
2.56.0.385.gd3acb90ef8-goog