From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Fri, 25 Jul 2025 17:06:45 +0000 (+0900)
Subject: core/exec-invoke: check size of read size
X-Git-Tag: v258-rc2~81^2~8
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1f4e9f6d605f9cee7ef43373cd307ffb1445e562;p=thirdparty%2Fsystemd.git

core/exec-invoke: check size of read size

Even though we do not use the read data, it is better to check the size
to prevent something spurious going.

Fixes CID#1612155.
---

diff --git a/src/core/exec-invoke.c b/src/core/exec-invoke.c
index dbac2958243..56facd94c3f 100644
--- a/src/core/exec-invoke.c
+++ b/src/core/exec-invoke.c
@@ -2244,8 +2244,11 @@ static int setup_private_users_child(int unshare_ready_fd, const char *uid_map,
 
         /* Wait until the parent unshared the user namespace */
         uint64_t c;
-        if (read(unshare_ready_fd, &c, sizeof(c)) < 0)
+        ssize_t n = read(unshare_ready_fd, &c, sizeof(c));
+        if (n < 0)
                 return log_debug_errno(errno, "Failed to read from signaling eventfd: %m");
+        if (n != sizeof(c))
+                return log_debug_errno(SYNTHETIC_ERRNO(EIO), "Short read from signaling eventfd.");
 
         /* Disable the setgroups() system call in the child user namespace, for good, unless PrivateUsers=full
          * and using the system service manager. */