On Nov 7, 2023 Roberto Sassu <roberto.sassu@xxxxxxxxxxxxxxx> wrote:
>
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the inode_post_removexattr hook.
>
> At inode_removexattr hook, EVM verifies the file's existing HMAC value. At
> inode_post_removexattr, EVM re-calculates the file's HMAC with the passed
> xattr removed and other file metadata.
>
> Other LSMs could similarly take some action after successful xattr removal.
>
> The new hook cannot return an error and cannot cause the operation to be
> reverted.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> ---
> fs/xattr.c | 9 +++++----
> include/linux/lsm_hook_defs.h | 2 ++
> include/linux/security.h | 5 +++++
> security/security.c | 14 ++++++++++++++
> 4 files changed, 26 insertions(+), 4 deletions(-)
...
> diff --git a/security/security.c b/security/security.c
> index ce3bc7642e18..8aa6e9f316dd 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2452,6 +2452,20 @@ int security_inode_removexattr(struct mnt_idmap *idmap,
> return evm_inode_removexattr(idmap, dentry, name);
> }
>
> +/**
> + * security_inode_post_removexattr() - Update the inode after a removexattr op
> + * @dentry: file
> + * @name: xattr name
> + *
> + * Update the inode after a successful removexattr operation.
> + */
> +void security_inode_post_removexattr(struct dentry *dentry, const char *name)
> +{
> + if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> + return;
Similar comment about the S_PRIVATE check as was in patch 10/23.
> + call_void_hook(inode_post_removexattr, dentry, name);
> +}
> +
> /**
> * security_inode_need_killpriv() - Check if security_inode_killpriv() required
> * @dentry: associated dentry
> --
> 2.34.1
--
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