cc314eef01
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>
97 lines
2 KiB
C
97 lines
2 KiB
C
/*
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* linux/fs/nfs/symlink.c
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*
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* Copyright (C) 1992 Rick Sladkey
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*
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* Optimization changes Copyright (C) 1994 Florian La Roche
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*
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* Jun 7 1999, cache symlink lookups in the page cache. -DaveM
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*
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* nfs symlink handling code
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*/
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#define NFS_NEED_XDR_TYPES
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#include <linux/time.h>
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#include <linux/errno.h>
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#include <linux/sunrpc/clnt.h>
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#include <linux/nfs.h>
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#include <linux/nfs2.h>
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#include <linux/nfs_fs.h>
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#include <linux/pagemap.h>
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#include <linux/stat.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/smp_lock.h>
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#include <linux/namei.h>
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/* Symlink caching in the page cache is even more simplistic
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* and straight-forward than readdir caching.
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*/
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static int nfs_symlink_filler(struct inode *inode, struct page *page)
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{
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int error;
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lock_kernel();
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error = NFS_PROTO(inode)->readlink(inode, page, 0, PAGE_SIZE);
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unlock_kernel();
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if (error < 0)
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goto error;
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SetPageUptodate(page);
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unlock_page(page);
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return 0;
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error:
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SetPageError(page);
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unlock_page(page);
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return -EIO;
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}
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static void *nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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struct inode *inode = dentry->d_inode;
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struct page *page;
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void *err = ERR_PTR(nfs_revalidate_inode(NFS_SERVER(inode), inode));
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if (err)
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goto read_failed;
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page = read_cache_page(&inode->i_data, 0,
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(filler_t *)nfs_symlink_filler, inode);
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if (IS_ERR(page)) {
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err = page;
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goto read_failed;
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}
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if (!PageUptodate(page)) {
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err = ERR_PTR(-EIO);
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goto getlink_read_error;
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}
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nd_set_link(nd, kmap(page));
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return page;
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getlink_read_error:
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page_cache_release(page);
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read_failed:
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nd_set_link(nd, err);
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return NULL;
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}
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static void nfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
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{
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if (cookie) {
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struct page *page = cookie;
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kunmap(page);
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page_cache_release(page);
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}
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}
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/*
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* symlinks can't do much...
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*/
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struct inode_operations nfs_symlink_inode_operations = {
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.readlink = generic_readlink,
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.follow_link = nfs_follow_link,
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.put_link = nfs_put_link,
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.getattr = nfs_getattr,
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.setattr = nfs_setattr,
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};
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