git: 2f5778abbe18 - stable/12 - Fix potential NULL pointer dereference of device physical path

[Warner Losh]

The branch stable/12 has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=2f5778abbe180dcb44eaf17db1fb915204249615

commit 2f5778abbe180dcb44eaf17db1fb915204249615
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 16:16:31 +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 5b789559468f..34a70a951a39 100644
--- a/sys/cam/ata/ata_xpt.c
+++ b/sys/cam/ata/ata_xpt.c
@@ -1757,9 +1757,11 @@ 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;
@@ -1768,6 +1770,7 @@ 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 68097a5e4e74..f3cf66f1ca19 100644
--- a/sys/cam/nvme/nvme_xpt.c
+++ b/sys/cam/nvme/nvme_xpt.c
@@ -683,9 +683,11 @@ 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;
@@ -694,6 +696,7 @@ 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;