git: c8b24162a4eb - stable/13 - Fix potential NULL pointer dereference of device physical path

[Warner Losh]

The branch stable/13 has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=c8b24162a4eb20484d4add7710a33ef6387111f7

commit c8b24162a4eb20484d4add7710a33ef6387111f7
Author:     Young Xiao <92siuyang at gmail.com>
AuthorDate: 2019-05-21 07:36:29 +0000
Commit:     Warner Losh <imp at FreeBSD.org>
CommitDate: 2021-07-21 16:13:10 +0000

    Fix potential NULL pointer dereference of device physical path
    
    In ata_dev_advinfo() and nvme_dev_advinfo(), if the physical path is
    being stored and there is a malloc failure (malloc(9) is called with
    M_NOWAIT), we could wind up in a situation where the device's
    physpath_len is set to the length the user provided, but the physpath
    itself is NULL.
    
    If another context then comes in to fetch the physical path value, we
    would wind up trying to memcpy a NULL pointer into the caller's buffer.
    
    So, set the physpath_len to 0 when we free the physpath on entry into
    the store case for the physical path.  Reset the length to a non-zero
    value only after we've successfully malloced a buffer to hold it.
    
    This code mirrors scsi_xpt.c does already as well.
    
    Signed-off-by:  Young Xiao <92siuyang at gmail.com>
    Reviewed by:    imp
    PR:             238014
    
    (cherry picked from commit 431ddd94360a9e86c91294eaa2c7b859911984b7)
---
 sys/cam/ata/ata_xpt.c   | 7 +++++--
 sys/cam/nvme/nvme_xpt.c | 7 +++++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/sys/cam/ata/ata_xpt.c b/sys/cam/ata/ata_xpt.c
index 559e9a234b87..a3be7470354f 100644
--- a/sys/cam/ata/ata_xpt.c
+++ b/sys/cam/ata/ata_xpt.c
@@ -1756,9 +1756,11 @@ ata_dev_advinfo(union ccb *start_ccb)
 		break;
 	case CDAI_TYPE_PHYS_PATH:
 		if (cdai->flags & CDAI_FLAG_STORE) {
-			if (device->physpath != NULL)
+			if (device->physpath != NULL) {
 				free(device->physpath, M_CAMXPT);
-			device->physpath_len = cdai->bufsiz;
+				device->physpath = NULL;
+				device->physpath_len = 0;
+			}
 			/* Clear existing buffer if zero length */
 			if (cdai->bufsiz == 0)
 				break;
@@ -1767,6 +1769,7 @@ ata_dev_advinfo(union ccb *start_ccb)
 				start_ccb->ccb_h.status = CAM_REQ_ABORTED;
 				return;
 			}
+			device->physpath_len = cdai->bufsiz;
 			memcpy(device->physpath, cdai->buf, cdai->bufsiz);
 		} else {
 			cdai->provsiz = device->physpath_len;
diff --git a/sys/cam/nvme/nvme_xpt.c b/sys/cam/nvme/nvme_xpt.c
index 126b284936bb..800d6aeb291e 100644
--- a/sys/cam/nvme/nvme_xpt.c
+++ b/sys/cam/nvme/nvme_xpt.c
@@ -682,9 +682,11 @@ nvme_dev_advinfo(union ccb *start_ccb)
 		break;
 	case CDAI_TYPE_PHYS_PATH:
 		if (cdai->flags & CDAI_FLAG_STORE) {
-			if (device->physpath != NULL)
+			if (device->physpath != NULL) {
 				free(device->physpath, M_CAMXPT);
-			device->physpath_len = cdai->bufsiz;
+				device->physpath = NULL;
+				device->physpath_len = 0;
+			}
 			/* Clear existing buffer if zero length */
 			if (cdai->bufsiz == 0)
 				break;
@@ -693,6 +695,7 @@ nvme_dev_advinfo(union ccb *start_ccb)
 				start_ccb->ccb_h.status = CAM_REQ_ABORTED;
 				return;
 			}
+			device->physpath_len = cdai->bufsiz;
 			memcpy(device->physpath, cdai->buf, cdai->bufsiz);
 		} else {
 			cdai->provsiz = device->physpath_len;