git: 95b86ac22728 - stable/12 - Fix race in case of device destruction.

[Alexander Motin]

The branch stable/12 has been updated by mav:

URL: https://cgit.FreeBSD.org/src/commit/?id=95b86ac2272885b4e1b9b3c2f0aafca7ea90fabc

commit 95b86ac2272885b4e1b9b3c2f0aafca7ea90fabc
Author:     Alexander Motin <mav at FreeBSD.org>
AuthorDate: 2021-04-13 15:19:10 +0000
Commit:     Alexander Motin <mav at FreeBSD.org>
CommitDate: 2021-04-27 12:48:57 +0000

    Fix race in case of device destruction.
    
    During device destruction it is possible that open() succeed, but
    fdevname() return NULL, that can't be assigned to string variable.
    Fix that by adding explicit NULL check.
    
    Also while there switch from fdevname() to fdevname_r().
    
    Sponsored by:   iXsystems, Inc.
    MFC after:      2 weeks
    
    (cherry picked from commit e49d3eb40324eaffaa13b93f2c4173dfa04dfa34)
---
 lib/libdevdctl/event.cc | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/libdevdctl/event.cc b/lib/libdevdctl/event.cc
index 36c9b725fed1..76ef1896975a 100644
--- a/lib/libdevdctl/event.cc
+++ b/lib/libdevdctl/event.cc
@@ -277,6 +277,7 @@ Event::GetTimestamp() const
 bool
 Event::DevPath(std::string &path) const
 {
+	char buf[SPECNAMELEN + 1];
 	string devName;
 
 	if (!DevName(devName))
@@ -288,7 +289,11 @@ Event::DevPath(std::string &path) const
 		return (false);
 
 	/* Normalize the device name in case the DEVFS event is for a link. */
-	devName = fdevname(devFd);
+	if (fdevname_r(devFd, buf, sizeof(buf)) == NULL) {
+		close(devFd);
+		return (false);
+	}
+	devName = buf;
 	path = _PATH_DEV + devName;
 
 	close(devFd);