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Commit 29333920 authored by Al Viro's avatar Al Viro
Browse files

Fix remount races with symlink handling in affs 



A couple of fields in affs_sb_info is used in follow_link() and
symlink() for handling AFFS "absolute" symlinks.  Need locking
against affs_remount() updates.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent afc70ed0

fs/affs/affs.h

+1 −1
Original line number Diff line number Diff line
@@ -106,8 +106,8 @@ struct affs_sb_info { 
	u32 s_last_bmap;

	struct buffer_head *s_bmap_bh;

	char *s_prefix;			/* Prefix for volumes and assigns. */

	int s_prefix_len;		/* Length of prefix. */

	char s_volume[32];		/* Volume prefix for absolute symlinks. */

	spinlock_t symlink_lock;	/* protects the previous two */

};



#define SF_INTL		0x0001		/* International filesystem. */

fs/affs/namei.c

+5 −2
Original line number Diff line number Diff line
@@ -341,10 +341,13 @@ affs_symlink(struct inode *dir, struct dentry *dentry, const char *symname) 
	p  = (char *)AFFS_HEAD(bh)->table;

	lc = '/';

	if (*symname == '/') {

		struct affs_sb_info *sbi = AFFS_SB(sb);

		while (*symname == '/')

			symname++;

		while (AFFS_SB(sb)->s_volume[i])	/* Cannot overflow */

			*p++ = AFFS_SB(sb)->s_volume[i++];

		spin_lock(&sbi->symlink_lock);

		while (sbi->s_volume[i])	/* Cannot overflow */

			*p++ = sbi->s_volume[i++];

		spin_unlock(&sbi->symlink_lock);

	}

	while (i < maxlen && (c = *symname++)) {

		if (c == '.' && lc == '/' && *symname == '.' && symname[1] == '/') {

fs/affs/super.c

+14 −3
Original line number Diff line number Diff line
@@ -221,8 +221,6 @@ parse_options(char *options, uid_t *uid, gid_t *gid, int *mode, int *reserved, s 
			*mount_opts |= SF_MUFS;

			break;

		case Opt_prefix:

			/* Free any previous prefix */

			kfree(*prefix);

			*prefix = match_strdup(&args[0]);

			if (!*prefix)

				return 0;
@@ -311,6 +309,7 @@ static int affs_fill_super(struct super_block *sb, void *data, int silent) 
		return -ENOMEM;

	sb->s_fs_info = sbi;

	mutex_init(&sbi->s_bmlock);

	spin_lock_init(&sbi->symlink_lock);



	if (!parse_options(data,&uid,&gid,&i,&reserved,&root_block,

				&blocksize,&sbi->s_prefix,
@@ -518,14 +517,18 @@ affs_remount(struct super_block *sb, int *flags, char *data) 
	unsigned long		 mount_flags;

	int			 res = 0;

	char			*new_opts = kstrdup(data, GFP_KERNEL);

	char			 volume[32];

	char			*prefix = NULL;



	pr_debug("AFFS: remount(flags=0x%x,opts=\"%s\")\n",*flags,data);



	*flags |= MS_NODIRATIME;



	memcpy(volume, sbi->s_volume, 32);

	if (!parse_options(data, &uid, &gid, &mode, &reserved, &root_block,

			   &blocksize, &sbi->s_prefix, sbi->s_volume,

			   &blocksize, &prefix, volume,

			   &mount_flags)) {

		kfree(prefix);

		kfree(new_opts);

		return -EINVAL;

	}
@@ -536,6 +539,14 @@ affs_remount(struct super_block *sb, int *flags, char *data) 
	sbi->s_mode  = mode;

	sbi->s_uid   = uid;

	sbi->s_gid   = gid;

	/* protect against readers */

	spin_lock(&sbi->symlink_lock);

	if (prefix) {

		kfree(sbi->s_prefix);

		sbi->s_prefix = prefix;

	}

	memcpy(sbi->s_volume, volume, 32);

	spin_unlock(&sbi->symlink_lock);



	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY)) {

		unlock_kernel();

fs/affs/symlink.c

+5 −2
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ static int affs_symlink_readpage(struct file *file, struct page *page) 
	int			 i, j;

	char			 c;

	char			 lc;

	char			*pf;



	pr_debug("AFFS: follow_link(ino=%lu)\n",inode->i_ino);
@@ -32,11 +31,15 @@ static int affs_symlink_readpage(struct file *file, struct page *page) 
	j  = 0;

	lf = (struct slink_front *)bh->b_data;

	lc = 0;

	pf = AFFS_SB(inode->i_sb)->s_prefix ? AFFS_SB(inode->i_sb)->s_prefix : "/";



	if (strchr(lf->symname,':')) {	/* Handle assign or volume name */

		struct affs_sb_info *sbi = AFFS_SB(inode->i_sb);

		char *pf;

		spin_lock(&sbi->symlink_lock);

		pf = sbi->s_prefix ? sbi->s_prefix : "/";

		while (i < 1023 && (c = pf[i]))

			link[i++] = c;

		spin_unlock(&sbi->symlink_lock);

		while (i < 1023 && lf->symname[j] != ':')

			link[i++] = lf->symname[j++];

		if (i < 1023)