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Commit b4c07bce authored by Lee Schermerhorn's avatar Lee Schermerhorn Committed by Linus Torvalds
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hugetlbfs: handle empty options string 



I was seeing a null pointer deref in fs/super.c:vfs_kern_mount().
Some file system get_sb() handler was returning NULL mnt_sb with
a non-negative return value.  I also noticed a "hugetlbfs: Bad
mount option:" message in the log.

Turns out that hugetlbfs_parse_options() was not checking for an
empty option string after call to strsep().  On failure,
hugetlbfs_parse_options() returns 1.  hugetlbfs_fill_super() just
passed this return code back up the call stack where
vfs_kern_mount() missed the error and proceeded with a NULL mnt_sb.

Apparently introduced by patch:
	hugetlbfs-use-lib-parser-fix-docs.patch

The problem was exposed by this line in my fstab:

none        /huge       hugetlbfs   defaults    0 0

It can also be demonstrated by invoking mount of hugetlbfs
directly with no options or a bogus option.

This patch:

1) adds the check for empty option to hugetlbfs_parse_options(),
2) enhances the error message to bracket any unrecognized
   option with quotes ,
3) modifies hugetlbfs_parse_options() to return -EINVAL on any
   unrecognized option,
4) adds a BUG_ON() to vfs_kern_mount() to catch any get_sb()
   handler that returns a NULL mnt->mnt_sb with a return value
   >= 0.

Signed-off-by: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e73a75fa

fs/hugetlbfs/inode.c

+5 −3
Original line number Original line Diff line number Diff line
@@ -621,6 +621,8 @@ hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig) 




	while ((p = strsep(&options, ",")) != NULL) {

	while ((p = strsep(&options, ",")) != NULL) {

		int token;

		int token;

		if (!*p)

			continue;





		token = match_token(p, tokens, args);

		token = match_token(p, tokens, args);

		switch (token) {

		switch (token) {
@@ -665,8 +667,9 @@ hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig) 
			break;

			break;





		default:

		default:

			printk(KERN_ERR "hugetlbfs: Bad mount option: %s\n", p);

			printk(KERN_ERR "hugetlbfs: Bad mount option: \"%s\"\n",

 			return 1;

				 p);

			return -EINVAL;

			break;

			break;

		}

		}

	}

	}
@@ -693,7 +696,6 @@ hugetlbfs_fill_super(struct super_block *sb, void *data, int silent) 
	config.gid = current->fsgid;

	config.gid = current->fsgid;

	config.mode = 0755;

	config.mode = 0755;

	ret = hugetlbfs_parse_options(data, &config);

	ret = hugetlbfs_parse_options(data, &config);



	if (ret)

	if (ret)

		return ret;

		return ret;

fs/super.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -884,6 +884,7 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void 
	error = type->get_sb(type, flags, name, data, mnt);

	error = type->get_sb(type, flags, name, data, mnt);

	if (error < 0)

	if (error < 0)

		goto out_free_secdata;

		goto out_free_secdata;

	BUG_ON(!mnt->mnt_sb);





 	error = security_sb_kern_mount(mnt->mnt_sb, secdata);

 	error = security_sb_kern_mount(mnt->mnt_sb, secdata);

 	if (error)

 	if (error)