mke2fs: disallow creating FS on a loop mounted file with no option

When /etc/mtab is a symlink of /proc/mounts, mke2fs without -FF option
can create a filesystem on the image file that is mounted.
According to mke2fs man page, we should specify -FF option in this case.

This patch protects filesystem from unintended mke2fs caused by human error.

How to reproduce:
  # mke2fs -t ext4 -Fq fs.img
  # mount -o loop fs.img /mnt/mp1
  # mke2fs -t ext4 -Fq fs.img && echo "mke2fs success"
  mke2fs success

Signed-off-by: Kazuya Mio <k-mio@sx.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/configure b/configure
index 738bd89e937ee62727a8354ac4432b6a53fdd907..31ec8d395df049517f642290c24ba8ed61769644 100755 (executable)
--- a/configure
+++ b/configure
@@ -10370,7 +10370,7 @@ fi
 done
 
 fi
-for ac_header in       dirent.h        errno.h         execinfo.h      getopt.h        malloc.h        mntent.h        paths.h         semaphore.h     setjmp.h        signal.h        stdarg.h        stdint.h        stdlib.h        termios.h       termio.h        unistd.h        utime.h         linux/falloc.h  linux/fd.h      linux/major.h   net/if_dl.h     netinet/in.h    sys/disklabel.h         sys/file.h      sys/ioctl.h     sys/mkdev.h     sys/mman.h      sys/prctl.h     sys/queue.h     sys/resource.h  sys/select.h    sys/socket.h    sys/sockio.h    sys/stat.h      sys/syscall.h   sys/sysmacros.h         sys/time.h      sys/types.h     sys/un.h        sys/wait.h
+for ac_header in       dirent.h        errno.h         execinfo.h      getopt.h        malloc.h        mntent.h        paths.h         semaphore.h     setjmp.h        signal.h        stdarg.h        stdint.h        stdlib.h        termios.h       termio.h        unistd.h        utime.h         linux/falloc.h  linux/fd.h      linux/major.h   linux/loop.h    net/if_dl.h     netinet/in.h    sys/disklabel.h         sys/file.h      sys/ioctl.h     sys/mkdev.h     sys/mman.h      sys/prctl.h     sys/queue.h     sys/resource.h  sys/select.h    sys/socket.h    sys/sockio.h    sys/stat.h      sys/syscall.h   sys/sysmacros.h         sys/time.h      sys/types.h     sys/un.h        sys/wait.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"

diff --git a/configure.in b/configure.in
index 87d73e4e9cf8c78019737422592ac7e693c32612..6f39cc983de6700c16964dd44b9e0b95a35d92fe 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -866,6 +866,7 @@ AC_CHECK_HEADERS(m4_flatten([
        linux/falloc.h
        linux/fd.h
        linux/major.h
+       linux/loop.h
        net/if_dl.h
        netinet/in.h
        sys/disklabel.h

diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
index 2c1bd752b3c13b59f541388b317e57284c4d14f9..6c6ecff0e21cd160b290b175756d21130bc25032 100644 (file)
--- a/lib/ext2fs/ismounted.c
+++ b/lib/ext2fs/ismounted.c
@@ -21,6 +21,13 @@
 #ifdef HAVE_LINUX_FD_H
 #include <linux/fd.h>
 #endif
+#ifdef HAVE_LINUX_LOOP_H
+#include <linux/loop.h>
+#include <sys/ioctl.h>
+#ifdef HAVE_LINUX_MAJOR_H
+#include <linux/major.h>
+#endif /* HAVE_LINUX_MAJOR_H */
+#endif /* HAVE_LINUX_LOOP_H */
 #ifdef HAVE_MNTENT_H
 #include <mntent.h>
 #endif
@@ -35,6 +42,36 @@
 #include "ext2_fs.h"
 #include "ext2fs.h"
 
+/*
+ * Check to see if a regular file is mounted.
+ * If /etc/mtab/ is a symlink of /proc/mounts, you will need the following check
+ * because the name in /proc/mounts is a loopback device not a regular file.
+ */
+static int check_loop_mounted(const char *mnt_fsname, dev_t mnt_rdev,
+                               dev_t file_dev, ino_t file_ino)
+{
+#if defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H)
+       struct loop_info64 loopinfo;
+       int loop_fd, ret;
+
+       if (major(mnt_rdev) == LOOP_MAJOR) {
+               loop_fd = open(mnt_fsname, O_RDONLY);
+               if (loop_fd < 0)
+                       return -1;
+
+               ret = ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo);
+               close(loop_fd);
+               if (ret < 0)
+                       return -1;
+
+               if (file_dev == loopinfo.lo_device &&
+                               file_ino == loopinfo.lo_inode)
+                       return 1;
+       }
+#endif /* defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H) */
+       return 0;
+}
+
 #ifdef HAVE_SETMNTENT
 /*
  * Helper function which checks a file in /etc/mtab format to see if a
@@ -82,6 +119,10 @@ static errcode_t check_mntent_file(const char *mtab_file, const char *file,
 #ifndef __GNU__
                                if (file_rdev && (file_rdev == st_buf.st_rdev))
                                        break;
+                               if (check_loop_mounted(mnt->mnt_fsname,
+                                               st_buf.st_rdev, file_dev,
+                                               file_ino) == 1)
+                                       break;
 #endif /* __GNU__ */
                        } else {
                                if (file_dev && ((file_dev == st_buf.st_dev) &&