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Commit d5e66348 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 4330ed8e

fs/nfs/file.c

+7 −4
Original line number Original line 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 */

	/* origin == SEEK_END => we must revalidate the cached file length */

	if (origin == SEEK_END) {

	if (origin == SEEK_END) {

		struct inode *inode = filp->f_mapping->host;

		struct inode *inode = filp->f_mapping->host;



		int retval = nfs_revalidate_file_size(inode, filp);

		int retval = nfs_revalidate_file_size(inode, filp);

		if (retval < 0)

		if (retval < 0)

			return (loff_t)retval;

			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);

		loff = generic_file_llseek_unlocked(filp, offset, origin);

	unlock_kernel();

	return loff;

	return loff;

}

}