From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 12 May 2021 11:45:48 +0000 (+0200)
Subject: terminal-util: add extra validity checks that we operate on a TTY before doing so
X-Git-Tag: v249-rc1~194^2~4
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e60a4a3c46df1abc6570a026d716c71a6cb1bf5c;p=thirdparty%2Fsystemd.git

terminal-util: add extra validity checks that we operate on a TTY before doing so

Prompted by #19213, but not fixing it.

This is mostly paranoia that we don't do stuff on inodes that aren't
actually ttys.
---

diff --git a/src/basic/terminal-util.c b/src/basic/terminal-util.c
index 91c404892ea..9bc6bb2024f 100644
--- a/src/basic/terminal-util.c
+++ b/src/basic/terminal-util.c
@@ -240,9 +240,11 @@ int reset_terminal_fd(int fd, bool switch_to_text) {
 
         assert(fd >= 0);
 
-        /* We leave locked terminal attributes untouched, so that
-         * Plymouth may set whatever it wants to set, and we don't
-         * interfere with that. */
+        if (isatty(fd) < 1)
+                return log_debug_errno(errno, "Asked to reset a terminal that actually isn't a terminal: %m");
+
+        /* We leave locked terminal attributes untouched, so that Plymouth may set whatever it wants to set,
+         * and we don't interfere with that. */
 
         /* Disable exclusive mode, just in case */
         if (ioctl(fd, TIOCNXCL) < 0)
@@ -1329,6 +1331,9 @@ int vt_restore(int fd) {
         };
         int r, q = 0;
 
+        if (isatty(fd) < 1)
+                return log_debug_errno(errno, "Asked to restore the VT for an fd that does not refer to a terminal: %m");
+
         if (ioctl(fd, KDSETMODE, KD_TEXT) < 0)
                 q = log_debug_errno(errno, "Failed to set VT in text mode, ignoring: %m");
 
@@ -1362,6 +1367,9 @@ int vt_release(int fd, bool restore) {
          * sent by the kernel and optionally reset the VT in text and auto
          * VT-switching modes. */
 
+        if (isatty(fd) < 1)
+                return log_debug_errno(errno, "Asked to release the VT for an fd that does not refer to a terminal: %m");
+
         if (ioctl(fd, VT_RELDISP, 1) < 0)
                 return -errno;