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SubjectRe: [PATCH 05/20] afs: Implement @sys substitution handling
Date
How about the attached changes?

Note that I've put the checks for ".", ".." and names containing '/' in the
functions where the strings for @sys and @cell are set.

David
---
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index a14ea4280590..5e3a0ed2043f 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -760,6 +760,55 @@ static struct inode *afs_do_lookup(struct inode *dir, struct dentry *dentry,
return inode;
}

+/*
+ * Do a parallel recursive lookup.
+ *
+ * Ideally, we'd call lookup_one_len(), but we can't because we'd need to be
+ * holding i_mutex but we only hold i_rwsem for read.
+ */
+struct dentry *afs_lookup_rec(struct dentry *dir, const char *name, int len)
+{
+ DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+ struct dentry *dentry, *old;
+ struct inode *inode = dir->d_inode;
+ struct qstr this;
+ int ret;
+
+ this.name = name;
+ this.len = len;
+ this.hash = full_name_hash(dir, name, len);
+
+ if (unlikely(IS_DEADDIR(inode)))
+ return ERR_PTR(-ESTALE);
+
+again:
+ dentry = d_alloc_parallel(dir, &this, &wq);
+ if (IS_ERR(dentry))
+ return ERR_CAST(dentry);
+
+ if (unlikely(!d_in_lookup(dentry))) {
+ ret = dentry->d_op->d_revalidate(dentry, 0);
+ if (unlikely(ret <= 0)) {
+ if (!ret) {
+ d_invalidate(dentry);
+ dput(dentry);
+ goto again;
+ }
+ dput(dentry);
+ dentry = ERR_PTR(ret);
+ }
+ } else {
+ old = inode->i_op->lookup(inode, dentry, 0);
+ d_lookup_done(dentry); /* Clean up wq */
+ if (unlikely(old)) {
+ dput(dentry);
+ dentry = old;
+ }
+ }
+
+ return dentry;
+}
+
/*
* Look up an entry in a directory with @sys substitution.
*/
@@ -810,7 +859,7 @@ static struct dentry *afs_lookup_atsys(struct inode *dir, struct dentry *dentry,
strcpy(p, name);
read_unlock(&net->sysnames_lock);

- ret = lookup_one_len(buf, parent, len);
+ ret = afs_lookup_rec(parent, buf, len);
if (IS_ERR(ret) || d_is_positive(ret))
goto out_b;
dput(ret);
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
index b70380e5d0e3..42d03a80310d 100644
--- a/fs/afs/dynroot.c
+++ b/fs/afs/dynroot.c
@@ -125,7 +125,7 @@ static struct dentry *afs_lookup_atcell(struct dentry *dentry)
if (!cell)
goto out_n;

- ret = lookup_one_len(name, parent, len);
+ ret = afs_lookup_rec(parent, name, len);
if (IS_ERR(ret) || d_is_positive(ret))
goto out_n;

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 70dd41e06363..1dbcdafb25a0 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -682,6 +682,7 @@ extern const struct inode_operations afs_dir_inode_operations;
extern const struct address_space_operations afs_dir_aops;
extern const struct dentry_operations afs_fs_dentry_operations;

+extern struct dentry *afs_lookup_rec(struct dentry *, const char *, int);
extern void afs_d_release(struct dentry *);

/*
diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index 870b0bad03d0..47a0ac21ee44 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -393,6 +393,12 @@ static ssize_t afs_proc_rootcell_write(struct file *file,
if (IS_ERR(kbuf))
return PTR_ERR(kbuf);

+ ret = -EINVAL;
+ if (kbuf[0] == '.')
+ goto out;
+ if (memchr(kbuf, '/', size))
+ goto out;
+
/* trim to first NL */
s = memchr(kbuf, '\n', size);
if (s)
@@ -405,6 +411,7 @@ static ssize_t afs_proc_rootcell_write(struct file *file,
if (ret >= 0)
ret = size; /* consume everything, always */

+out:
kfree(kbuf);
_leave(" = %d", ret);
return ret;
@@ -775,27 +782,28 @@ static ssize_t afs_proc_sysname_write(struct file *file,
len = strlen(s);
if (len == 0)
continue;
- if (len >= AFSNAMEMAX) {
- sysnames->error = -ENAMETOOLONG;
- ret = -ENAMETOOLONG;
- goto out;
- }
+ ret = -ENAMETOOLONG;
+ if (len >= AFSNAMEMAX)
+ goto error;
+
if (len >= 4 &&
s[len - 4] == '@' &&
s[len - 3] == 's' &&
s[len - 2] == 'y' &&
- s[len - 1] == 's') {
+ s[len - 1] == 's')
/* Protect against recursion */
- sysnames->error = -EINVAL;
- ret = -EINVAL;
- goto out;
- }
+ goto invalid;
+
+ if (s[0] == '.' &&
+ (len < 2 || (len == 2 && s[1] == '.')))
+ goto invalid;
+
+ if (memchr(s, '/', len))
+ goto invalid;

- if (sysnames->nr >= AFS_NR_SYSNAME) {
- sysnames->error = -EFBIG;
- ret = -EFBIG;
+ ret = -EFBIG;
+ if (sysnames->nr >= AFS_NR_SYSNAME)
goto out;
- }

if (strcmp(s, afs_init_sysname) == 0) {
sub = (char *)afs_init_sysname;
@@ -815,6 +823,12 @@ static ssize_t afs_proc_sysname_write(struct file *file,
inode_unlock(file_inode(file));
kfree(kbuf);
return ret;
+
+invalid:
+ ret = -EINVAL;
+error:
+ sysnames->error = ret;
+ goto out;
}

static int afs_proc_sysname_release(struct inode *inode, struct file *file)
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