From 47fbe49861392b049dc9f4826b2d75cf6e8a1ba3 Mon Sep 17 00:00:00 2001
From: Joachim Wiberg <troglobit@gmail.com>
Date: Mon, 14 Jun 2021 11:20:08 +0200
Subject: [PATCH] Wrap all mount(2) calls so we at least get an error message

If any of these mount() calls fail, not counting EBUSY because that
would mean sth is already mounted, there really isn't much we can do.
So the least we should do is warn on console if it happens.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
---
 src/finit.c | 37 ++++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/src/finit.c b/src/finit.c
index 54f34d59..055ad8dc 100644
--- a/src/finit.c
+++ b/src/finit.c
@@ -156,6 +156,18 @@ static int fsck_all(void)
 	return rc;
 }
 
+/* Wrapper for mount(2), logs any errors to stderr */
+static void fs_mount(const char *src, const char *tgt, const char *fstype,
+		     unsigned long flags, const void *data)
+{
+	const char *msg = !fstype ? "MS_MOVE" : "mounting";
+	int rc;
+
+	rc = mount(src, tgt, fstype, flags, data);
+	if (rc && errno != EBUSY)
+		_pe("Failed %s %s on %s", msg, src, tgt);
+}
+
 #ifndef SYSROOT
 /* If / is not listed in fstab, or listed as 'ro', leave it alone */
 static int fs_readonly_root(struct fstab *fs)
@@ -207,8 +219,7 @@ static void fs_remount_root(int fsckerr)
 	 * XXX: Untested, in the initramfs age we should
 	 *      probably use switch_root instead.
 	 */
-	if (mount(SYSROOT, "/", NULL, MS_MOVE, NULL))
-		_pe("Failed %s / MS_MOVE");
+	fs_mount(SYSROOT, "/", NULL, MS_MOVE, NULL);
 }
 #endif	/* SYSROOT */
 
@@ -232,7 +243,7 @@ static void fs_finalize(void)
 	 */
 	if (!fismnt("/dev/shm")) {
 		makedir("/dev/shm", 0777);
-		mount("shm", "/dev/shm", "tmpfs", 0, "mode=0777");
+		fs_mount("shm", "/dev/shm", "tmpfs", 0, "mode=0777");
 	}
 
 	/* Modern systems use /dev/pts */
@@ -250,7 +261,7 @@ static void fs_finalize(void)
 		snprintf(opts, sizeof(opts), "gid=%d,mode=%d,ptmxmode=0666", gid, mode);
 
 		makedir("/dev/pts", 0755);
-		mount("devpts", "/dev/pts", "devpts", MS_NOSUID | MS_NOEXEC, opts);
+		fs_mount("devpts", "/dev/pts", "devpts", MS_NOSUID | MS_NOEXEC, opts);
 	}
 
 	/*
@@ -263,19 +274,19 @@ static void fs_finalize(void)
 	 * for /run (and optionally /run/lock).
 	 */
 	if (fisdir("/run") && !fismnt("/run")) {
-		mount("tmpfs", "/run", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, "mode=0755,size=10%");
+		fs_mount("tmpfs", "/run", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, "mode=0755,size=10%");
 
 		/* This prevents user DoS of /run by filling /run/lock at the expense of another tmpfs, max 5MiB */
 		makedir("/run/lock", 1777);
-		mount("tmpfs", "/run/lock", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, "mode=0777,size=5252880");
+		fs_mount("tmpfs", "/run/lock", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, "mode=0777,size=5252880");
 	}
 
 	/* Modern systems use tmpfs for /tmp */
 	if (!fismnt("/tmp"))
-		mount("tmpfs", "/tmp", "tmpfs", MS_NOSUID | MS_NODEV, "mode=1777");
+		fs_mount("tmpfs", "/tmp", "tmpfs", MS_NOSUID | MS_NODEV, "mode=1777");
 }
 
-static void fs_mount(void)
+static void fs_mount_all(void)
 {
 	if (!rescue)
 		fs_remount_root(fsck_all());
@@ -299,7 +310,7 @@ static void fs_mount(void)
  * We need /proc for rs_remount_root() and conf_parse_cmdline(), /dev
  * for early multi-console, and /sys for the cgroups support.  Any
  * occurrence of these file systems in /etc/fstab will replace these
- * mounts later in fs_mount()
+ * mounts later in fs_mount_all()
  *
  * Ignore any mount errors with EBUSY, kernel likely alread mounted
  * the filesystem for us automatically, e.g., CONFIG_DEVTMPFS_MOUNT.
@@ -319,8 +330,6 @@ static void fs_init(void)
 	umask(022);
 
 	for (i = 0; i < NELEMS(fs); i++) {
-		int rc;
-
 		/*
 		 * Check if already mounted, we may be running in a
 		 * container, or an initramfs ran before us.  The
@@ -330,9 +339,7 @@ static void fs_init(void)
 		if (fismnt(fs[i].file))
 			continue;
 
-		rc = mount(fs[i].spec, fs[i].file, fs[i].type, 0, NULL);
-		if (rc && errno != EBUSY)
-			_pe("Failed mounting %s on %s", fs[i].spec, fs[i].file);
+		fs_mount(fs[i].spec, fs[i].file, fs[i].type, 0, NULL);
 	}
 }
 
@@ -608,7 +615,7 @@ int main(int argc, char *argv[])
 	cgroup_init(&loop);
 
 	/* Check and mount filesystems. */
-	fs_mount();
+	fs_mount_all();
 
 	/* Bootstrap conditions, needed for hooks */
 	cond_init();