Commit d5e66348 authored Sep 23, 2008 by Trond Myklebust

NFS: Fix nfs_file_llseek()

After the BKL removal patches were applied to the rest of the NFS code, the
BKL protection in nfs_file_llseek() is no longer sufficient to ensure that
inode->i_size is read safely in generic_file_llseek_unlocked().

In order to fix the situation, we either have to replace the naked read of
inode->i_size in generic_file_llseek_unlocked() with i_size_read(), or the
whole thing needs to be executed under the inode->i_lock;
In order to avoid disrupting other filesystems, avoid touching
generic_file_llseek_unlocked() for now...

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

parent 4330ed8e

fs/nfs/file.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -188,13 +188,16 @@ static loff_t nfs_file_llseek(struct file *filp, loff_t offset, int origin)
		/* origin == SEEK_END => we must revalidate the cached file length */
		if (origin == SEEK_END) {
		struct inode *inode = filp->f_mapping->host;

		int retval = nfs_revalidate_file_size(inode, filp);
		if (retval < 0)
		return (loff_t)retval;
		}
		lock_kernel(); /* BKL needed? */

		spin_lock(&inode->i_lock);
		loff = generic_file_llseek_unlocked(filp, offset, origin);
		spin_unlock(&inode->i_lock);
		} else
		loff = generic_file_llseek_unlocked(filp, offset, origin);
		unlock_kernel();
		return loff;
		}

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