Merge pull request #31181 from fbuihuu/gpt-auto-more-defensive

gpt-auto-generator: be more defensive when checking the presence of E…

NEWS

@@ -13,6 +13,13 @@ CHANGES WITH 256 in spe:
           section, then all assigned VLAN IDs on the interface that are not
           configured in the .network file are removed.
 
+        * systemd-gpt-auto-generator will stop generating units for ESP or
+          XBOOTLDR partitions if it finds mount entries in the /boot/ or /efi/
+          hierarchies in fstab. This is to prevent the generator from
+          interfering with systems where ESP is explicitly configured to be
+          mounted at some path, for example /boot/efi/ (this type of setup is
+          obsolete but is still commonly found).
+
         Network Management:
 
         * systemd-networkd's proxy support gained a new option to configure

man/systemd-gpt-auto-generator.xml

@@ -32,18 +32,22 @@
 
     <para><filename>systemd-gpt-auto-generator</filename> is a unit generator that automatically discovers
     the root partition, <filename>/home/</filename>, <filename>/srv/</filename>, <filename>/var/</filename>,
-    <filename>/var/tmp/</filename>, the EFI System Partition, the Extended Boot Loader Partition, and swap
+    <filename>/var/tmp/</filename>, the EFI System Partition (ESP), the Extended Boot Loader Partition
-    partitions and creates mount and swap units for them, based on the partition type GUIDs of GUID partition
+    (XBOOTLDR), and swap partitions and creates mount and swap units for them, based on the partition type
-    tables (GPT). See <ulink url="https://uefi.org/specifications">UEFI Specification</ulink>, chapter 5 for
+    GUIDs of GUID partition tables (GPT). See <ulink url="https://uefi.org/specifications">UEFI
-    more details. It implements the <ulink
+    Specification</ulink>, chapter 5 for more details. It implements the <ulink
     url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable
     Partitions Specification</ulink>.</para>
 
     <para>Note that this generator has no effect on non-GPT systems. It will also not create mount point
     configuration for directories which already contain files or if the mount point is explicitly configured
     in <citerefentry
-    project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>. If
+    project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Additionally
-    the units this generator creates are overridden, for example by units in directories with higher
+    no unit will be created for the ESP or the XBOOTLDR partition if mount entries are found in the
+    <filename>/boot/</filename> or <filename>/efi/</filename> hierarchies in <citerefentry
+    project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+
+    <para>If the units this generator creates are overridden, for example by units in directories with higher
     precedence, drop-ins and additional dependencies created by this generator might still be used.</para>
 
     <para>This generator will only look for the root partition on the same physical disk where the EFI System

src/gpt-auto-generator/gpt-auto-generator.c

@@ -463,18 +463,6 @@ static int add_automount(
         return generator_add_symlink(arg_dest, SPECIAL_LOCAL_FS_TARGET, "wants", unit);
 }
 
-static int slash_boot_in_fstab(void) {
-        static int cache = -1;
-
-        if (cache >= 0)
-                return cache;
-
-        cache = fstab_is_mount_point("/boot");
-        if (cache < 0)
-                return log_error_errno(cache, "Failed to parse fstab: %m");
-        return cache;
-}
-
 static int add_partition_xbootldr(DissectedPartition *p) {
         _cleanup_free_ char *options = NULL;
         int r;
@@ -486,14 +474,6 @@ static int add_partition_xbootldr(DissectedPartition *p) {
                 return 0;
         }
 
-        r = slash_boot_in_fstab();
-        if (r < 0)
-                return r;
-        if (r > 0) {
-                log_debug("/boot/ specified in fstab, ignoring XBOOTLDR partition.");
-                return 0;
-        }
-
         r = path_is_busy("/boot");
         if (r < 0)
                 return r;
@@ -523,18 +503,6 @@ static int add_partition_xbootldr(DissectedPartition *p) {
 }
 
 #if ENABLE_EFI
-static int slash_efi_in_fstab(void) {
-        static int cache = -1;
-
-        if (cache >= 0)
-                return cache;
-
-        cache = fstab_is_mount_point("/efi");
-        if (cache < 0)
-                return log_error_errno(cache, "Failed to parse fstab: %m");
-        return cache;
-}
-
 static bool slash_boot_exists(void) {
         static int cache = -1;
 
@@ -574,27 +542,16 @@ static int add_partition_esp(DissectedPartition *p, bool has_xbootldr) {
          * Otherwise, if /efi/ is unused and empty (or missing), we'll take that.
          * Otherwise, we do nothing. */
         if (!has_xbootldr && slash_boot_exists()) {
-                r = slash_boot_in_fstab();
+                r = path_is_busy("/boot");
                 if (r < 0)
                         return r;
                 if (r == 0) {
-                        r = path_is_busy("/boot");
+                        esp_path = "/boot";
-                        if (r < 0)
+                        id = "boot";
-                                return r;
-                        if (r == 0) {
-                                esp_path = "/boot";
-                                id = "boot";
-                        }
                 }
         }
 
         if (!esp_path) {
-                r = slash_efi_in_fstab();
-                if (r < 0)
-                        return r;
-                if (r > 0)
-                        return 0;
-
                 r = path_is_busy("/efi");
                 if (r < 0)
                         return r;
@@ -781,6 +738,18 @@ static int process_loader_partitions(DissectedPartition *esp, DissectedPartition
         assert(esp);
         assert(xbootldr);
 
+        /* If any paths in fstab look similar to our favorite paths for ESP or XBOOTLDR, we just exit
+         * early. We also don't bother with cases where one is configured explicitly and the other shall be
+         * mounted automatically. */
+
+        r = fstab_has_mount_point_prefix_strv(STRV_MAKE("/boot", "/efi"));
+        if (r > 0) {
+                log_debug("Found mount entries in the /boot/ or /efi/ hierarchies in fstab, not generating ESP or XBOOTLDR mounts.");
+                return 0;
+        }
+        if (r < 0)
+                log_debug_errno(r, "Failed to check fstab existing paths, ignoring: %m");
+
         if (!is_efi_boot()) {
                 log_debug("Not an EFI boot, skipping loader partition UUID check.");
                 goto mount;

src/shared/fstab-util.c

@@ -105,6 +105,34 @@ static int fstab_is_same_node(const char *what_fstab, const char *path) {
         return false;
 }
 
+int fstab_has_mount_point_prefix_strv(char **prefixes) {
+        _cleanup_endmntent_ FILE *f = NULL;
+
+        assert(prefixes);
+
+        /* This function returns true if at least one entry in fstab has a mount point that starts with one
+         * of the passed prefixes. */
+
+        if (!fstab_enabled())
+                return false;
+
+        f = setmntent(fstab_path(), "re");
+        if (!f)
+                return errno == ENOENT ? false : -errno;
+
+        for (;;) {
+                struct mntent *me;
+
+                errno = 0;
+                me = getmntent(f);
+                if (!me)
+                        return errno != 0 ? -errno : false;
+
+                if (path_startswith_strv(me->mnt_dir, prefixes))
+                        return true;
+        }
+}
+
 int fstab_is_mount_point_full(const char *where, const char *path) {
         _cleanup_endmntent_ FILE *f = NULL;
         int r;

src/shared/fstab-util.h

@@ -25,6 +25,8 @@ static inline int fstab_has_node(const char *path) {
         return fstab_is_mount_point_full(NULL, path);
 }
 
+int fstab_has_mount_point_prefix_strv(char **prefixes);
+
 int fstab_filter_options(
                 const char *opts,
                 const char *names,