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authorLinus Torvalds <torvalds@g5.osdl.org>2005-08-20 05:02:56 +0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-08-20 05:02:56 +0400
commitcc314eef0128a807e50fa03baf2d0abc0647952c (patch)
tree8e38db1be28006894915273b3f3cb3beaa6efda3 /fs/namei.c
parent2fb1e3086df9b454538491fba8121298da37cd23 (diff)
downloadlinux-cc314eef0128a807e50fa03baf2d0abc0647952c.tar.xz
Fix nasty ncpfs symlink handling bug.
This bug could cause oopses and page state corruption, because ncpfs used the generic page-cache symlink handlign functions. But those functions only work if the page cache is guaranteed to be "stable", ie a page that was installed when the symlink walk was started has to still be installed in the page cache at the end of the walk. We could have fixed ncpfs to not use the generic helper routines, but it is in many ways much cleaner to instead improve on the symlink walking helper routines so that they don't require that absolute stability. We do this by allowing "follow_link()" to return a error-pointer as a cookie, which is fed back to the cleanup "put_link()" routine. This also simplifies NFS symlink handling. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c40
1 files changed, 21 insertions, 19 deletions
diff --git a/fs/namei.c b/fs/namei.c
index b85f158aef0c..6ec1f0fefc5b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -501,6 +501,7 @@ struct path {
static inline int __do_follow_link(struct path *path, struct nameidata *nd)
{
int error;
+ void *cookie;
struct dentry *dentry = path->dentry;
touch_atime(path->mnt, dentry);
@@ -508,13 +509,15 @@ static inline int __do_follow_link(struct path *path, struct nameidata *nd)
if (path->mnt == nd->mnt)
mntget(path->mnt);
- error = dentry->d_inode->i_op->follow_link(dentry, nd);
- if (!error) {
+ cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
+ error = PTR_ERR(cookie);
+ if (!IS_ERR(cookie)) {
char *s = nd_get_link(nd);
+ error = 0;
if (s)
error = __vfs_follow_link(nd, s);
if (dentry->d_inode->i_op->put_link)
- dentry->d_inode->i_op->put_link(dentry, nd);
+ dentry->d_inode->i_op->put_link(dentry, nd, cookie);
}
dput(dentry);
mntput(path->mnt);
@@ -2344,15 +2347,17 @@ out:
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct nameidata nd;
- int res;
+ void *cookie;
+
nd.depth = 0;
- res = dentry->d_inode->i_op->follow_link(dentry, &nd);
- if (!res) {
- res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
+ cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
+ if (!IS_ERR(cookie)) {
+ int res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
if (dentry->d_inode->i_op->put_link)
- dentry->d_inode->i_op->put_link(dentry, &nd);
+ dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
+ cookie = ERR_PTR(res);
}
- return res;
+ return PTR_ERR(cookie);
}
int vfs_follow_link(struct nameidata *nd, const char *link)
@@ -2395,23 +2400,20 @@ int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
return res;
}
-int page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
+void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
{
- struct page *page;
+ struct page *page = NULL;
nd_set_link(nd, page_getlink(dentry, &page));
- return 0;
+ return page;
}
-void page_put_link(struct dentry *dentry, struct nameidata *nd)
+void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
- if (!IS_ERR(nd_get_link(nd))) {
- struct page *page;
- page = find_get_page(dentry->d_inode->i_mapping, 0);
- if (!page)
- BUG();
+ struct page *page = cookie;
+
+ if (page) {
kunmap(page);
page_cache_release(page);
- page_cache_release(page);
}
}