Commit 0499d672 authored by Chuck Lever's avatar Chuck Lever Committed by Yu Kuai
Browse files

libfs: Add simple_offset_empty() 

mainline inclusion
from mainline-v6.9-rc1
commit ecba88a3b32d733d41e27973e25b2bc580f64281
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAR5GW
CVE: CVE-2024-46701

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ecba88a3b32d733d41e27973e25b2bc580f64281



--------------------------------

For simple filesystems that use directory offset mapping, rely
strictly on the directory offset map to tell when a directory has
no children.

After this patch is applied, the emptiness test holds only the RCU
read lock when the directory being tested has no children.

In addition, this adds another layer of confirmation that
simple_offset_add/remove() are working as expected.

Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Link: https://lore.kernel.org/r/170820143463.6328.7872919188371286951.stgit@91.116.238.104.host.secureserver.net


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
parent 0a47eeb3

fs/libfs.c

+32 −0
Original line number Diff line number Diff line
@@ -312,6 +312,38 @@ void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry) 
	offset_set(dentry, 0);

}



/**

 * simple_offset_empty - Check if a dentry can be unlinked

 * @dentry: dentry to be tested

 *

 * Returns 0 if @dentry is a non-empty directory; otherwise returns 1.

 */

int simple_offset_empty(struct dentry *dentry)

{

	struct inode *inode = d_inode(dentry);

	struct offset_ctx *octx;

	struct dentry *child;

	unsigned long index;

	int ret = 1;



	if (!inode || !S_ISDIR(inode->i_mode))

		return ret;



	index = DIR_OFFSET_MIN;

	octx = inode->i_op->get_offset_ctx(inode);

	xa_for_each(&octx->xa, index, child) {

		spin_lock(&child->d_lock);

		if (simple_positive(child)) {

			spin_unlock(&child->d_lock);

			ret = 0;

			break;

		}

		spin_unlock(&child->d_lock);

	}



	return ret;

}



/**

 * simple_offset_rename_exchange - exchange rename with directory offsets

 * @old_dir: parent of dentry being moved

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -3262,6 +3262,7 @@ struct offset_ctx { 
void simple_offset_init(struct offset_ctx *octx);

int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry);

void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry);

int simple_offset_empty(struct dentry *dentry);

int simple_offset_rename_exchange(struct inode *old_dir,

				  struct dentry *old_dentry,

				  struct inode *new_dir,

mm/shmem.c

+2 −2
Original line number Diff line number Diff line
@@ -3543,7 +3543,7 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry) 


static int shmem_rmdir(struct inode *dir, struct dentry *dentry)

{

	if (!simple_empty(dentry))

	if (!simple_offset_empty(dentry))

		return -ENOTEMPTY;



	drop_nlink(d_inode(dentry));
@@ -3600,7 +3600,7 @@ static int shmem_rename2(struct mnt_idmap *idmap, 
		return simple_offset_rename_exchange(old_dir, old_dentry,

						     new_dir, new_dentry);



	if (!simple_empty(new_dentry))

	if (!simple_offset_empty(new_dentry))

		return -ENOTEMPTY;



	if (flags & RENAME_WHITEOUT) {