linux-ext4 - 答复: [PATCH v2] e2fsprogs: Check device id in advance to skip fake device name

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Date:   Mon, 11 Nov 2019 14:43:46 +0000
From:   Guiyao <guiyao@...wei.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
CC:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        Mingfangsen <mingfangsen@...wei.com>,
        "ebiggers@...gle.com" <ebiggers@...gle.com>,
        "aceballos@...il.com" <aceballos@...il.com>,
        "vertaling@...vern.nl" <vertaling@...vern.nl>
Subject: 答复: [PATCH v2] e2fsprogs: Check device id in advance to skip fake device name

Hi Theodore,

Thanks for your response and your rewriting.

Actually, we found some insane system administrators, they not only do something like "mount -t tmpfs /dev/sdb /tmp ", but also they do " ln -s /dev/sdb abc ", then "resize2fs abc xxx". :(

So we have to add the fixing code in both sides of "name matched" and "name not matched".

For the compiling issue, it's my fault in previous patch, and added the macro in a wrong line.

So, I rewrote it again, and please give more advise. Thank you in advance.


diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
index 6cd497d..729769e 100644
--- a/lib/ext2fs/ismounted.c
+++ b/lib/ext2fs/ismounted.c
@@ -97,6 +97,9 @@ static errcode_t check_mntent_file(const char *mtab_file, const char *file,
                   int *mount_flags, char *mtpt, int mtlen)
 {
    struct mntent   *mnt;
+#ifndef __GNU__
+   struct stat dir_st_buf;
+#endif  /* __GNU__ */
    struct stat st_buf;
    errcode_t   retval = 0;
    dev_t       file_dev=0, file_rdev=0;
@@ -128,13 +131,32 @@ static errcode_t check_mntent_file(const char *mtab_file, const char *file,
    while ((mnt = getmntent (f)) != NULL) {
        if (mnt->mnt_fsname[0] != '/')
            continue;
-       if (strcmp(file, mnt->mnt_fsname) == 0)
+#ifndef __GNU__
+       if (stat(mnt->mnt_dir, &dir_st_buf) != 0)
+           continue;
+#endif
+       if (strcmp(file, mnt->mnt_fsname) == 0) {
+#ifndef __GNU__
+           if (file_rdev && (file_rdev != dir_st_buf.st_dev)) {
+#ifdef DEBUG
+               printf("Bogus entry in %s!  "
+                      "(%s does not exist)\n",
+                      mtab_file, mnt->mnt_dir);
+#endif /* DEBUG */
+               continue;
+           }
+#endif /* __GNU__ */
            break;
+       }
+
        if (stat(mnt->mnt_fsname, &st_buf) == 0) {
            if (ext2fsP_is_disk_device(st_buf.st_mode)) {
 #ifndef __GNU__
-               if (file_rdev && (file_rdev == st_buf.st_rdev))
-                   break;
+               if (file_rdev && (file_rdev == st_buf.st_rdev)) {
+                   if (file_rdev == dir_st_buf.st_dev)
+                       break;
+               }
+
                if (check_loop_mounted(mnt->mnt_fsname,
                        st_buf.st_rdev, file_dev,
                        file_ino) == 1)
@@ -168,32 +190,6 @@ static errcode_t check_mntent_file(const char *mtab_file, const char *file,
 #endif /* __GNU__ */
        goto errout;
    }
-#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
-   /* Validate the entry in case /etc/mtab is out of date */
-   /*
-    * We need to be paranoid, because some broken distributions
-    * (read: Slackware) don't initialize /etc/mtab before checking
-    * all of the non-root filesystems on the disk.
-    */
-   if (stat(mnt->mnt_dir, &st_buf) < 0) {
-       retval = errno;
-       if (retval == ENOENT) {
-#ifdef DEBUG
-           printf("Bogus entry in %s!  (%s does not exist)\n",
-                  mtab_file, mnt->mnt_dir);
-#endif /* DEBUG */
-           retval = 0;
-       }
-       goto errout;
-   }
-   if (file_rdev && (st_buf.st_dev != file_rdev)) {
-#ifdef DEBUG
-       printf("Bogus entry in %s!  (%s not mounted on %s)\n",
-              mtab_file, file, mnt->mnt_dir);
-#endif /* DEBUG */
-       goto errout;
-   }
-#endif /* __GNU__ */
    *mount_flags = EXT2_MF_MOUNTED;

 #ifdef MNTOPT_RO
-- 
1.8.3.1