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>

1 files changed, 5 insertions, 2 deletions

diff --git a/fs/affs/symlink.c b/fs/affs/symlink.c
index 41782539c907..ee00f08c4f53 100644
--- a/fs/affs/symlink.c
+++ b/fs/affs/symlink.c
@@ -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)