--- /dev/null
+From b00674347337b7531c92fdb65590ab253bb57538 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
+Date: Wed, 23 Jun 2021 11:46:41 +0200
+Subject: [PATCH] basic/unit-name: do not use strdupa() on a path
+
+The path may have unbounded length, for example through a fuse mount.
+
+CVE-2021-33910: attacked controlled alloca() leads to crash in systemd and
+ultimately a kernel panic. Systemd parses the content of /proc/self/mountinfo
+and each mountpoint is passed to mount_setup_unit(), which calls
+unit_name_path_escape() underneath. A local attacker who is able to mount a
+filesystem with a very long path can crash systemd and the whole system.
+
+https://bugzilla.redhat.com/show_bug.cgi?id=1970887
+
+The resulting string length is bounded by UNIT_NAME_MAX, which is 256. But we
+can't easily check the length after simplification before doing the
+simplification, which in turns uses a copy of the string we can write to.
+So we can't reject paths that are too long before doing the duplication.
+Hence the most obvious solution is to switch back to strdup(), as before
+7410616cd9dbbec97cf98d75324da5cda2b2f7a2.
+
+(cherry picked from commit 441e0115646d54f080e5c3bb0ba477c892861ab9)
+(cherry picked from commit 764b74113e36ac5219a4b82a05f311b5a92136ce)
+(cherry picked from commit 4a1c5f34bd3e1daed4490e9d97918e504d19733b)
+
+CVE: CVE-2021-33910
+Upstream-Status: Backport [b00674347337b7531c92fdb65590ab253bb57538]
+Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
+---
+ src/basic/unit-name.c | 13 +++++--------
+ 1 file changed, 5 insertions(+), 8 deletions(-)
+
+diff --git a/src/basic/unit-name.c b/src/basic/unit-name.c
+index 5f595af944..9b6cacde87 100644
+--- a/src/basic/unit-name.c
++++ b/src/basic/unit-name.c
+@@ -378,12 +378,13 @@ int unit_name_unescape(const char *f, char **ret) {
+ }
+
+ int unit_name_path_escape(const char *f, char **ret) {
+- char *p, *s;
++ _cleanup_free_ char *p = NULL;
++ char *s;
+
+ assert(f);
+ assert(ret);
+
+- p = strdupa(f);
++ p = strdup(f);
+ if (!p)
+ return -ENOMEM;
+
+@@ -395,13 +396,9 @@ int unit_name_path_escape(const char *f, char **ret) {
+ if (!path_is_normalized(p))
+ return -EINVAL;
+
+- /* Truncate trailing slashes */
++ /* Truncate trailing slashes and skip leading slashes */
+ delete_trailing_chars(p, "/");
+-
+- /* Truncate leading slashes */
+- p = skip_leading_chars(p, "/");
+-
+- s = unit_name_escape(p);
++ s = unit_name_escape(skip_leading_chars(p, "/"));
+ }
+ if (!s)
+ return -ENOMEM;
+--
+2.33.0
+
