rpcdebug: avoid buffer underflow (RHEL-7931)

commit c1c35487aba2cec828d9b8a1be9043000beadea5
Author: Lixiaokeng <lixiaokeng@huawei.com>
Date:   Mon Oct 24 13:00:50 2022 -0400

    blkmapd: fix coredump in bl_add_disk

Signed-off-by: Steve Dickson <steved@redhat.com>
Resolves: RHEL-7941

nfs-utils-2.5.4-rpcdebug-check-read-return.patch

@@ -0,0 +1,24 @@
+commit a746c35822e557766d1871ec976490a71e6962d9
+Author: Zhi Li <yieli@redhat.com>
+Date:   Wed Apr 5 12:08:10 2023 -0400
+
+    rpcdebug: avoid buffer underflow if read() returns 0
+    
+    Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2176740
+    
+    Signed-off-by: Zhi Li <yieli@redhat.com>
+    Signed-off-by: Steve Dickson <steved@redhat.com>
+
+diff --git a/tools/rpcdebug/rpcdebug.c b/tools/rpcdebug/rpcdebug.c
+index 68206cc5..ec05179e 100644
+--- a/tools/rpcdebug/rpcdebug.c
++++ b/tools/rpcdebug/rpcdebug.c
+@@ -257,7 +257,7 @@ get_flags(char *module)
+ 		perror(filename);
+ 		exit(1);
+ 	}
+-	if ((len = read(sysfd, buffer, sizeof(buffer))) < 0) {
++	if ((len = read(sysfd, buffer, sizeof(buffer))) <= 0) {
+ 		perror("read");
+ 		exit(1);
+ 	}

nfs-utils.spec

@@ -57,6 +57,7 @@ Patch021: nfs-utils-2.5.4-mount-mountconf-typo.patch
 Patch022: nfs-utils-2.5.4-support-for-rpc-with-tls.patch
 Patch023: nfs-utils-2.5.4-fix-typos-in-messages.patch
 Patch024: nfs-utils-2.5.4-blkmapd-double-free.patch
+Patch025: nfs-utils-2.5.4-rpcdebug-check-read-return.patch
 
 Patch100: nfs-utils-1.2.1-statdpath-man.patch
 Patch101: nfs-utils-1.2.1-exp-subtree-warn-off.patch
@@ -498,9 +499,10 @@ fi
 %{_mandir}/*/nfsiostat.8.gz
 
 %changelog
-* Mon Feb  5 2024 Steve Dickson <steved@redhat.com> 2.5.4-23
+* Tus Feb  6 2024 Steve Dickson <steved@redhat.com> 2.5.4-23
 - Typos and documentation fixes (RHEL-22654)
 - blkmapd: fix coredump in bl_add_disk (RHEL-7941)
+- rpcdebug: avoid buffer underflow (RHEL-7931)
 
 * Thu Feb  1 2024 Steve Dickson <steved@redhat.com> 2.5.4-22
 - nfsmount.conf: Fix typo of the attribute name (RHEL-7904)