On Wed, May 13, 2026 at 10:52:45AM +0200, Daniel Vacek wrote:
> From: Omar Sandoval <[email protected]>
>
> fscrypt stores a context item with encrypted inodes that contains the
> related encryption information. fscrypt provides an arbitrary blob for
> the filesystem to store, and it does not clearly fit into an existing
> structure, so this goes in a new item type.
>
> Signed-off-by: Omar Sandoval <[email protected]>
> Signed-off-by: Sweet Tea Dorminy <[email protected]>
> Signed-off-by: Josef Bacik <[email protected]>
> Signed-off-by: Daniel Vacek <[email protected]>
> ---
>
> v7 changes:
> * Fix a path leak as found by Chri's AI review.
> v6 changes:
> * Shorten the inode context key macro name to BTRFS_FSCRYPT_INODE_CTX_KEY.
> v5:
> https://lore.kernel.org/linux-btrfs/5a88efb484b0874a7430b83bc6e5f6b9aa5858d5.1706116485.git.jo...@toxicpanda.com/
> ---
> fs/btrfs/fscrypt.c | 116 ++++++++++++++++++++++++++++++++
> fs/btrfs/fscrypt.h | 2 +
> fs/btrfs/inode.c | 19 ++++++
> fs/btrfs/ioctl.c | 8 ++-
> include/uapi/linux/btrfs_tree.h | 10 +++
> 5 files changed, 153 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/fscrypt.c b/fs/btrfs/fscrypt.c
> index 6cfba7d94e72..c503f817cbe7 100644
> --- a/fs/btrfs/fscrypt.c
> +++ b/fs/btrfs/fscrypt.c
> @@ -1,10 +1,126 @@
> // SPDX-License-Identifier: GPL-2.0
>
> +#include <linux/iversion.h>
> #include "ctree.h"
> +#include "accessors.h"
> #include "btrfs_inode.h"
> +#include "disk-io.h"
> +#include "fs.h"
> #include "fscrypt.h"
> +#include "ioctl.h"
> +#include "messages.h"
> +#include "transaction.h"
> +#include "xattr.h"
> +
> +static int btrfs_fscrypt_get_context(struct inode *inode, void *ctx, size_t
> len)
> +{
> + struct btrfs_key key = {
> + .objectid = btrfs_ino(BTRFS_I(inode)),
> + .type = BTRFS_FSCRYPT_INODE_CTX_KEY,
> + .offset = 0,
> + };
> + struct btrfs_path *path;
> + struct extent_buffer *leaf;
> + unsigned long ptr;
> + int ret;
> +
> +
> + path = btrfs_alloc_path();
> + if (!path)
> + return -ENOMEM;
> +
> + ret = btrfs_search_slot(NULL, BTRFS_I(inode)->root, &key, path, 0, 0);
> + if (ret) {
> + len = -ENOENT;
> + goto out;
> + }
> +
> + leaf = path->nodes[0];
> + ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
> + /* fscrypt provides max context length, but it could be less */
> + len = min_t(size_t, len, btrfs_item_size(leaf, path->slots[0]));
> + read_extent_buffer(leaf, ctx, ptr, len);
> +
> +out:
> + btrfs_free_path(path);
> + return len;
> +}
This doesn't conform to the calling convention for
fscrypt_operations::get_context, specifically in the cases where
-ENODATA and -ERANGE are expected.
/*
* Get the fscrypt context of the given inode.
*
* @inode: the inode whose context to get
* @ctx: the buffer into which to get the context
* @len: length of the @ctx buffer in bytes
*
* Return: On success, returns the length of the context in bytes; this
* may be less than @len. On failure, returns -ENODATA if the
* inode doesn't have a context, -ERANGE if the context is
* longer than @len, or another -errno code.
*/
int (*get_context)(struct inode *inode, void *ctx, size_t len);
It also seems to be assuming that any error from btrfs_search_slot()
means "not found", which isn't correct.
The size_t variable called 'len' is also being used to store negative
errno values, which is weird.
> +static int btrfs_fscrypt_set_context(struct inode *inode, const void *ctx,
> + size_t len, void *fs_data)
> +{
> + struct btrfs_trans_handle *trans = fs_data;
> + struct btrfs_key key = {
> + .objectid = btrfs_ino(BTRFS_I(inode)),
> + .type = BTRFS_FSCRYPT_INODE_CTX_KEY,
> + .offset = 0,
> + };
> + struct btrfs_path *path = NULL;
> + struct extent_buffer *leaf;
> + unsigned long ptr;
> + int ret;
> +
> + if (!trans)
> + trans = btrfs_start_transaction(BTRFS_I(inode)->root, 2);
> + if (IS_ERR(trans))
> + return PTR_ERR(trans);
> +
> + path = btrfs_alloc_path();
> + if (!path) {
> + ret = -ENOMEM;
> + goto out_err;
> + }
> +
> + ret = btrfs_search_slot(trans, BTRFS_I(inode)->root, &key, path, 0, 1);
> + if (ret < 0)
> + goto out_err;
> +
> + if (ret > 0) {
> + btrfs_release_path(path);
> + ret = btrfs_insert_empty_item(trans, BTRFS_I(inode)->root,
> path, &key, len);
> + if (ret)
> + goto out_err;
> + }
> +
> + leaf = path->nodes[0];
> + ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
> +
> + len = min_t(size_t, len, btrfs_item_size(leaf, path->slots[0]));
> + write_extent_buffer(leaf, ctx, ptr, len);
> + btrfs_mark_buffer_dirty(trans, leaf);
> + btrfs_release_path(path);
> +
> + if (fs_data)
> + goto out_err;
> +
> + BTRFS_I(inode)->flags |= BTRFS_INODE_ENCRYPT;
> + btrfs_sync_inode_flags_to_i_flags(BTRFS_I(inode));
> + inode_inc_iversion(inode);
> + inode_set_ctime_current(inode);
> + ret = btrfs_update_inode(trans, BTRFS_I(inode));
> + if (ret)
> + goto out_abort;
> + btrfs_free_path(path);
> + btrfs_end_transaction(trans);
> + return 0;
> +out_abort:
> + btrfs_abort_transaction(trans, ret);
> +out_err:
> + if (!fs_data)
> + btrfs_end_transaction(trans);
> + btrfs_free_path(path);
> + return ret;
> +}
The 'len = min_t(size_t, len, btrfs_item_size(leaf, path->slots[0]));'
line seems scary, since it just truncates the data given.
> @@ -199,7 +203,7 @@ static int check_fsflags(unsigned int old_flags, unsigned
> int flags)
> FS_NOATIME_FL | FS_NODUMP_FL | \
> FS_SYNC_FL | FS_DIRSYNC_FL | \
> FS_NOCOMP_FL | FS_COMPR_FL |
> - FS_NOCOW_FL))
> + FS_NOCOW_FL | FS_ENCRYPT_FL))
> return -EOPNOTSUPP;
Do you know why FS_VERITY_FL isn't in this mask?
- Eric
