Re: [PATCH v2 11/25] security: add hooks for set/get/remove of fscaps

Roberto Sassu
2024-03-01T15:59:56Z

On Wed, 2024-02-21 at 15:24 -0600, Seth Forshee (DigitalOcean) wrote:
> In preparation for moving fscaps out of the xattr code paths, add new
> security hooks. These hooks are largely needed because common kernel
> code will pass around struct vfs_caps pointers, which EVM will need to
> convert to raw xattr data for verification and updates of its hashes.
>
> Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org>
> ---
> include/linux/lsm_hook_defs.h | 7 +++++
> include/linux/security.h | 33 +++++++++++++++++++++
> security/security.c | 69 +++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 109 insertions(+)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 76458b6d53da..7b3c23f9e4a5 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -152,6 +152,13 @@ LSM_HOOK(int, 0, inode_get_acl, struct mnt_idmap *idmap,
> struct dentry *dentry, const char *acl_name)
> LSM_HOOK(int, 0, inode_remove_acl, struct mnt_idmap *idmap,
> struct dentry *dentry, const char *acl_name)
> +LSM_HOOK(int, 0, inode_set_fscaps, struct mnt_idmap *idmap,
> + struct dentry *dentry, const struct vfs_caps *caps, int flags);
> +LSM_HOOK(void, LSM_RET_VOID, inode_post_set_fscaps, struct mnt_idmap *idmap,
> + struct dentry *dentry, const struct vfs_caps *caps, int flags);
> +LSM_HOOK(int, 0, inode_get_fscaps, struct mnt_idmap *idmap, struct dentry *dentry);
> +LSM_HOOK(int, 0, inode_remove_fscaps, struct mnt_idmap *idmap,
> + struct dentry *dentry);

Uhm, there should not be semicolons here.

Roberto

> LSM_HOOK(int, 0, inode_need_killpriv, struct dentry *dentry)
> LSM_HOOK(int, 0, inode_killpriv, struct mnt_idmap *idmap,
> struct dentry *dentry)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index d0eb20f90b26..40be548e5e12 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -378,6 +378,13 @@ int security_inode_getxattr(struct dentry *dentry, const char *name);
> int security_inode_listxattr(struct dentry *dentry);
> int security_inode_removexattr(struct mnt_idmap *idmap,
> struct dentry *dentry, const char *name);
> +int security_inode_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
> + const struct vfs_caps *caps, int flags);
> +void security_inode_post_set_fscaps(struct mnt_idmap *idmap,
> + struct dentry *dentry,
> + const struct vfs_caps *caps, int flags);
> +int security_inode_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry);
> +int security_inode_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry);
> int security_inode_need_killpriv(struct dentry *dentry);
> int security_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry);
> int security_inode_getsecurity(struct mnt_idmap *idmap,
> @@ -935,6 +942,32 @@ static inline int security_inode_removexattr(struct mnt_idmap *idmap,
> return cap_inode_removexattr(idmap, dentry, name);
> }
>
> +static inline int security_inode_set_fscaps(struct mnt_idmap *idmap,
> + struct dentry *dentry,
> + const struct vfs_caps *caps,
> + int flags)
> +{
> + return 0;
> +}
> +static void security_inode_post_set_fscaps(struct mnt_idmap *idmap,
> + struct dentry *dentry,
> + const struct vfs_caps *caps,
> + int flags)
> +{
> +}
> +
> +static int security_inode_get_fscaps(struct mnt_idmap *idmap,
> + struct dentry *dentry)
> +{
> + return 0;
> +}
> +
> +static int security_inode_remove_fscaps(struct mnt_idmap *idmap,
> + struct dentry *dentry)
> +{
> + return 0;
> +}
> +
> static inline int security_inode_need_killpriv(struct dentry *dentry)
> {
> return cap_inode_need_killpriv(dentry);
> diff --git a/security/security.c b/security/security.c
> index 3aaad75c9ce8..0d210da9862c 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2351,6 +2351,75 @@ int security_inode_remove_acl(struct mnt_idmap *idmap,
> return evm_inode_remove_acl(idmap, dentry, acl_name);
> }
>
> +/**
> + * security_inode_set_fscaps() - Check if setting fscaps is allowed
> + * @idmap: idmap of the mount
> + * @dentry: file
> + * @caps: fscaps to be written
> + * @flags: flags for setxattr
> + *
> + * Check permission before setting the file capabilities given in @vfs_caps.
> + *
> + * Return: Returns 0 if permission is granted.
> + */
> +int security_inode_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
> + const struct vfs_caps *caps, int flags)
> +{
> + if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> + return 0;
> + return call_int_hook(inode_set_fscaps, 0, idmap, dentry, caps, flags);
> +}
> +
> +/**
> + * security_inode_post_set_fscaps() - Update the inode after setting fscaps
> + * @idmap: idmap of the mount
> + * @dentry: file
> + * @caps: fscaps to be written
> + * @flags: flags for setxattr
> + *
> + * Update inode security field after successfully setting fscaps.
> + *
> + */
> +void security_inode_post_set_fscaps(struct mnt_idmap *idmap,
> + struct dentry *dentry,
> + const struct vfs_caps *caps, int flags)
> +{
> + if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> + return;
> + call_void_hook(inode_post_set_fscaps, idmap, dentry, caps, flags);
> +}
> +
> +/**
> + * security_inode_get_fscaps() - Check if reading fscaps is allowed
> + * @dentry: file
> + *
> + * Check permission before getting fscaps.
> + *
> + * Return: Returns 0 if permission is granted.
> + */
> +int security_inode_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry)
> +{
> + if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> + return 0;
> + return call_int_hook(inode_get_fscaps, 0, idmap, dentry);
> +}
> +
> +/**
> + * security_inode_remove_fscaps() - Check if removing fscaps is allowed
> + * @idmap: idmap of the mount
> + * @dentry: file
> + *
> + * Check permission before removing fscaps.
> + *
> + * Return: Returns 0 if permission is granted.
> + */
> +int security_inode_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry)
> +{
> + if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> + return 0;
> + return call_int_hook(inode_remove_fscaps, 0, idmap, dentry);
> +}
> +
> /**
> * security_inode_post_setxattr() - Update the inode after a setxattr operation
> * @dentry: file
>