libmount: support MS_RDONLY on write-protected devices

This feature is supported by mount(8) only. It seems better move
this code to libmount. The results is more simple mount(8) and the
feature is accessible for all libmount users.

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libmount/docs/libmount-sections.txt b/libmount/docs/libmount-sections.txt
index 78d89cae7a65174f6dcb13be5c1d6dde6bbaec9f..1d21879a00f7a13287f123a21ddc2ead1c7136b4 100644 (file)
--- a/libmount/docs/libmount-sections.txt
+++ b/libmount/docs/libmount-sections.txt
@@ -35,8 +35,10 @@ mnt_context_enable_fork
 mnt_context_enable_lazy
 mnt_context_enable_loopdel
 mnt_context_enable_rdonly_umount
+mnt_context_enable_rwonly_mount;
 mnt_context_enable_sloppy
 mnt_context_enable_verbose
+mnt_context_forced_rdonly;
 mnt_context_get_cache
 mnt_context_get_fs
 mnt_context_get_fstab
@@ -72,6 +74,7 @@ mnt_context_is_nomtab
 mnt_context_is_parent
 mnt_context_is_rdonly_umount
 mnt_context_is_restricted
+mnt_context_is_rwonly_mount;
 mnt_context_is_sloppy
 mnt_context_is_swapmatch
 mnt_context_is_verbose

diff --git a/libmount/src/context.c b/libmount/src/context.c
index e731749b4200a1647feb940682bed8e001128ca5..6a7c7d35185e40bf9e9393d4a5b68867e7bef0fd 100644 (file)
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -172,6 +172,7 @@ int mnt_reset_context(struct libmnt_context *cxt)
        cxt->flags |= (fl & MNT_FL_FORCE);
        cxt->flags |= (fl & MNT_FL_NOCANONICALIZE);
        cxt->flags |= (fl & MNT_FL_RDONLY_UMOUNT);
+       cxt->flags |= (fl & MNT_FL_RWONLY_MOUNT);
        cxt->flags |= (fl & MNT_FL_NOSWAPMATCH);
        cxt->flags |= (fl & MNT_FL_TABPATHS_CHECKED);
        return 0;
@@ -477,6 +478,48 @@ int mnt_context_is_rdonly_umount(struct libmnt_context *cxt)
        return cxt->flags & MNT_FL_RDONLY_UMOUNT ? 1 : 0;
 }
 
+/**
+ * mnt_context_enable_rwonly_mount:
+ * @cxt: mount context
+ * @enable: TRUE or FALSE
+ *
+ * Force read-write mount; if enabled libmount will never try MS_RDONLY
+ * after failed mount(2) EROFS. (See mount(8) man page, option -w).
+ *
+ * Returns: 0 on success, negative number in case of error.
+ */
+int mnt_context_enable_rwonly_mount(struct libmnt_context *cxt, int enable)
+{
+       return set_flag(cxt, MNT_FL_RWONLY_MOUNT, enable);
+}
+
+/**
+ * mnt_context_is_rwonly_mount
+ * @cxt: mount context
+ *
+ * See also mnt_context_enable_rwonly_mount() and mount(8) man page,
+ * option -w.
+ *
+ * Returns: 1 if only read-write mount is allowed.
+ */
+int mnt_context_is_rwonly_mount(struct libmnt_context *cxt)
+{
+       return cxt->flags & MNT_FL_RWONLY_MOUNT ? 1 : 0;
+}
+
+/**
+ * mnt_context_forced_rdonly:
+ * @cxt: mount context
+ *
+ * See also mnt_context_enable_rwonly_mount().
+ *
+ * Returns: 1 if mounted read-only on write-protected device.
+ */
+int mnt_context_forced_rdonly(struct libmnt_context *cxt)
+{
+       return cxt->flags & MNT_FL_FORCED_RDONLY ? 1 : 0;
+}
+
 /**
  * mnt_context_disable_helpers:
  * @cxt: mount context
@@ -2002,8 +2045,10 @@ int mnt_context_apply_fstab(struct libmnt_context *cxt)
        if (!cxt || !cxt->fs)
                return -EINVAL;
 
-       if (mnt_context_tab_applied(cxt))       /* already applied */
+       if (mnt_context_tab_applied(cxt)) {     /* already applied */
+               DBG(CXT, ul_debugobj(cxt, "fstab already applied -- skip"));
                return 0;
+       }
 
        if (mnt_context_is_restricted(cxt)) {
                DBG(CXT, ul_debugobj(cxt, "force fstab usage for non-root users!"));

diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c
index 6368e9ba816e101b3e1a702c31d4f67b6b642d11..1c8a629243a4bafa9ea21557ee7c9bcb99aa237d 100644 (file)
--- a/libmount/src/context_mount.c
+++ b/libmount/src/context_mount.c
@@ -1083,6 +1083,7 @@ int mnt_context_mount(struct libmnt_context *cxt)
        assert(cxt->helper_exec_status == 1);
        assert(cxt->syscall_status == 1);
 
+again:
        rc = mnt_context_prepare_mount(cxt);
        if (!rc)
                rc = mnt_context_prepare_update(cxt);
@@ -1090,6 +1091,32 @@ int mnt_context_mount(struct libmnt_context *cxt)
                rc = mnt_context_do_mount(cxt);
        if (!rc)
                rc = mnt_context_update_tabs(cxt);
+
+       /*
+        * Read-only device; try mount filesystem read-only
+        */
+       if ((rc == -EROFS && !mnt_context_syscall_called(cxt))  /* before syscall; rdonly loopdev */
+            || mnt_context_get_syscall_errno(cxt) == EROFS     /* syscall failed with EROFS */
+            || mnt_context_get_syscall_errno(cxt) == EACCES)   /* syscall failed with EACCES */
+       {
+               unsigned long mflags = 0;
+
+               mnt_context_get_mflags(cxt, &mflags);
+
+               if (!(mflags & MS_RDONLY)                       /* not yet RDONLY */
+                   && !(mflags & MS_REMOUNT)                   /* not remount */
+                   && !(mflags & MS_BIND)                      /* not bin mount */
+                   && !mnt_context_is_rwonly_mount(cxt)) {     /* no explicit read-write */
+
+                       assert(!(cxt->flags & MNT_FL_FORCED_RDONLY));
+                       DBG(CXT, ul_debugobj(cxt, "write-protected source, trying RDONLY."));
+
+                       mnt_context_reset_status(cxt);
+                       mnt_context_set_mflags(cxt, mflags | MS_RDONLY);
+                       cxt->flags |= MNT_FL_FORCED_RDONLY;
+                       goto again;
+               }
+       }
        return rc;
 }
 

diff --git a/libmount/src/libmount.h.in b/libmount/src/libmount.h.in
index f191a52fe0334f53078497b5b290a33442c889ed..3f2da3230897d5b4ca7306612b4f1dd4ed0acaa2 100644 (file)
--- a/libmount/src/libmount.h.in
+++ b/libmount/src/libmount.h.in
@@ -610,6 +610,7 @@ extern int mnt_context_set_optsmode(struct libmnt_context *cxt, int mode);
 extern int mnt_context_disable_canonicalize(struct libmnt_context *cxt, int disable);
 extern int mnt_context_enable_lazy(struct libmnt_context *cxt, int enable);
 extern int mnt_context_enable_rdonly_umount(struct libmnt_context *cxt, int enable);
+extern int mnt_context_enable_rwonly_mount(struct libmnt_context *cxt, int enable);
 extern int mnt_context_disable_helpers(struct libmnt_context *cxt, int disable);
 extern int mnt_context_enable_sloppy(struct libmnt_context *cxt, int enable);
 extern int mnt_context_enable_fake(struct libmnt_context *cxt, int enable);
@@ -626,6 +627,8 @@ extern int mnt_context_is_lazy(struct libmnt_context *cxt)
                        __ul_attribute__((nonnull));
 extern int mnt_context_is_rdonly_umount(struct libmnt_context *cxt)
                        __ul_attribute__((nonnull));
+extern int mnt_context_is_rwonly_mount(struct libmnt_context *cxt)
+                       __ul_attribute__((nonnull));
 extern int mnt_context_is_sloppy(struct libmnt_context *cxt)
                        __ul_attribute__((nonnull));
 extern int mnt_context_is_fake(struct libmnt_context *cxt)
@@ -644,6 +647,8 @@ extern int mnt_context_is_nocanonicalize(struct libmnt_context *cxt)
                        __ul_attribute__((nonnull));
 extern int mnt_context_is_swapmatch(struct libmnt_context *cxt)
                        __ul_attribute__((nonnull));
+extern int mnt_context_forced_rdonly(struct libmnt_context *cxt)
+                       __ul_attribute__((nonnull));
 
 extern int mnt_context_is_fork(struct libmnt_context *cxt)
                        __ul_attribute__((nonnull));

diff --git a/libmount/src/libmount.sym b/libmount/src/libmount.sym
index f0210c240a575cc5ddcf4936a9ff8b71cf0a9834..354332b43a4c457fa137df79fdedeadd4e6b50fd 100644 (file)
--- a/libmount/src/libmount.sym
+++ b/libmount/src/libmount.sym
@@ -315,3 +315,9 @@ MOUNT_2.28 {
        mnt_table_find_target_with_option;
        mnt_fs_set_priority;
 } MOUNT_2.26;
+
+MOUNT_2.30 {
+       mnt_context_is_rwonly_mount;
+       mnt_context_forced_rdonly;
+       mnt_context_enable_rwonly_mount;
+} MOUNT_2.28;

diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index 2baab55de5202077a67291c821d1ea2cc53fb076..42957ecb9e30c380052d3139d5602da75643c83b 100644 (file)
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -328,6 +328,7 @@ struct libmnt_context
 #define MNT_FL_RDONLY_UMOUNT   (1 << 11)       /* remount,ro after EBUSY umount(2) */
 #define MNT_FL_FORK            (1 << 12)
 #define MNT_FL_NOSWAPMATCH     (1 << 13)
+#define MNT_FL_RWONLY_MOUNT    (1 << 14)       /* explicit mount -w; never try read-only  */
 
 #define MNT_FL_MOUNTDATA       (1 << 20)
 #define MNT_FL_TAB_APPLIED     (1 << 21)       /* mtab/fstab merged to cxt->fs */
@@ -338,6 +339,7 @@ struct libmnt_context
 #define MNT_FL_LOOPDEV_READY   (1 << 26)       /* /dev/loop<N> initialized by the library */
 #define MNT_FL_MOUNTOPTS_FIXED  (1 << 27)
 #define MNT_FL_TABPATHS_CHECKED        (1 << 28)
+#define MNT_FL_FORCED_RDONLY   (1 << 29)       /* mounted read-only on write-protected device */
 
 /* default flags */
 #define MNT_FL_DEFAULT         0

diff --git a/sys-utils/mount.8 b/sys-utils/mount.8
index 56ccbbd35e3c97e4cfc831b99ec25addc5a13a95..bbfe71b75ca6ece9e167d34893f7372ca82e4f8f 100644 (file)
--- a/sys-utils/mount.8
+++ b/sys-utils/mount.8
@@ -807,8 +807,12 @@ Mount the partition that has the specified
 Verbose mode.
 .TP
 .BR \-w , " \-\-rw" , " \-\-read\-write"
-Mount the filesystem read/write.  This is the default.  A synonym is
+Mount the filesystem read/write. The read-write is kernel default.  A synonym is
 .BR "\-o rw" .
+
+Note that specify \fB\-w\fR on command line forces \fBmount\fR command
+to never try read-only mount on write-protected devices. The default is
+try read-only if the previous mount syscall with read-write flags failed.
 .TP
 .BR \-V , " \-\-version"
 Display version information and exit.

diff --git a/sys-utils/mount.c b/sys-utils/mount.c
index b09e776161948c861714aa862844dcd83803310c..bdf6e4bdb6e07ed56f33731d8d8488598133d80e 100644 (file)
--- a/sys-utils/mount.c
+++ b/sys-utils/mount.c
@@ -51,8 +51,6 @@
  *  --options-source-force                             MNT_OMODE_FORCE
  */
 
-static int readwrite;
-
 static int mk_exit_code(struct libmnt_context *cxt, int rc);
 
 static void __attribute__((__noreturn__)) exit_non_root(const char *option)
@@ -369,7 +367,6 @@ static int mk_exit_code(struct libmnt_context *cxt, int rc)
        const char *tgt = mnt_context_get_target(cxt);
        const char *src = mnt_context_get_source(cxt);
 
-try_readonly:
        if (mnt_context_helper_executed(cxt)) {
                /*
                 * /sbin/mount.<type> called, return status
@@ -385,6 +382,9 @@ try_readonly:
                 */
                selinux_warning(cxt, tgt);
 
+               if (mnt_context_forced_rdonly(cxt))
+                       warnx(_("WARNING: device write-protected, mounted read-only"));
+
                return MOUNT_EX_SUCCESS;        /* mount(2) success */
        }
 
@@ -404,13 +404,14 @@ try_readonly:
                        return MOUNT_EX_USAGE;
                /* -EROFS before syscall can happen only for loop mount */
                case -EROFS:
-                       warnx(_("%s is used as read only loop, mounting read-only"), src);
-                       mnt_context_reset_status(cxt);
-                       mnt_context_set_mflags(cxt, mflags | MS_RDONLY);
-                       rc = mnt_context_mount(cxt);
-                       if (!rc)
-                               rc = mnt_context_finalize_mount(cxt);
-                       goto try_readonly;
+                       if (mflags & MS_RDONLY)
+                               warnx(_("cannot mount %s read-only"), src);
+                       else if (mnt_context_is_rwonly_mount(cxt))
+                               warnx(_("%s is write-protected but explicit `-w' flag given"), src);
+                       else if (mflags & MS_REMOUNT)
+                               warnx(_("cannot remount %s read-write, is write-protected"), src);
+                       warnx(_("mount %s on %s failed"), src, tgt);
+                       return MOUNT_EX_USAGE;
                case -MNT_ERR_NOFSTAB:
                        if (mnt_context_is_swapmatch(cxt)) {
                                warnx(_("can't find %s in %s"),
@@ -481,7 +482,6 @@ try_readonly:
         */
        syserr = mnt_context_get_syscall_errno(cxt);
 
-
        switch(syserr) {
        case EPERM:
                if (geteuid() == 0) {
@@ -620,27 +620,11 @@ try_readonly:
        case EROFS:
                if (mflags & MS_RDONLY)
                        warnx(_("cannot mount %s read-only"), src);
-
-               else if (readwrite)
+               else if (mnt_context_is_rwonly_mount(cxt))
                        warnx(_("%s is write-protected but explicit `-w' flag given"), src);
-
                else if (mflags & MS_REMOUNT)
                        warnx(_("cannot remount %s read-write, is write-protected"), src);
-
-               else if (mflags & MS_BIND)
-                       warn(_("mount %s on %s failed"), src, tgt);
-
-               else {
-                       warnx(_("%s is write-protected, mounting read-only"), src);
-
-                       mnt_context_reset_status(cxt);
-                       mnt_context_set_mflags(cxt, mflags | MS_RDONLY);
-                       rc = mnt_context_do_mount(cxt);
-                       if (!rc)
-                               rc = mnt_context_finalize_mount(cxt);
-
-                       goto try_readonly;
-               }
+               warnx(_("mount %s on %s failed"), src, tgt);
                break;
 
        case ENOMEDIUM:
@@ -924,7 +908,7 @@ int main(int argc, char **argv)
                        break;
                case 'r':
                        append_option(cxt, "ro");
-                       readwrite = 0;
+                       mnt_context_enable_rwonly_mount(cxt, FALSE);
                        break;
                case 'v':
                        mnt_context_enable_verbose(cxt, TRUE);
@@ -934,7 +918,7 @@ int main(int argc, char **argv)
                        break;
                case 'w':
                        append_option(cxt, "rw");
-                       readwrite = 1;
+                       mnt_context_enable_rwonly_mount(cxt, TRUE);
                        break;
                case 'o':
                        append_option(cxt, optarg);