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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: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2010-01-24 00:04:07 -05:00
parent afc70ed05a
commit 29333920a5
4 changed files with 25 additions and 8 deletions
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2
fs/affs/affs.h
View File

@ -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. */

7
fs/affs/namei.c
View File

@ -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] == '/') {

17
fs/affs/super.c
View File

@ -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();

7
fs/affs/symlink.c
View File

@ -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)