Re: [PATCH 1/3] evm: calculate HMAC after initializing posix acl

From: Casey Schaufler
Date: Wed Apr 24 2013 - 13:00:43 EST


On 4/24/2013 5:10 AM, Mimi Zohar wrote:
> (Reposting with expanded 'cc' list.)
>
> Included in the EVM hmac calculation is the i_mode. Any changes to
> the i_mode need to be reflected in the hmac. shmem_mknod() currently
> calls posix_acl_init(), which modifies the i_mode, after calling
> security_inode_init_security(). This patch reverses the order in
> which they are called.

I haven't tried this with Smack, but I don't anticipate any issues.

> Reported-by: Sven Vermeulen <sven.vermeulen@xxxxxxxxx>
> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxx>
> ---
> mm/shmem.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 1c44af7..398c195 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1937,6 +1937,13 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
>
> inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
> if (inode) {
> +#ifdef CONFIG_TMPFS_POSIX_ACL
> + error = generic_acl_init(inode, dir);
> + if (error) {
> + iput(inode);
> + return error;
> + }
> +#endif
> error = security_inode_init_security(inode, dir,
> &dentry->d_name,
> shmem_initxattrs, NULL);
> @@ -1946,15 +1953,8 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
> return error;
> }
> }
> -#ifdef CONFIG_TMPFS_POSIX_ACL
> - error = generic_acl_init(inode, dir);
> - if (error) {
> - iput(inode);
> - return error;
> - }
> -#else
> +
> error = 0;
> -#endif
> dir->i_size += BOGO_DIRENT_SIZE;
> dir->i_ctime = dir->i_mtime = CURRENT_TIME;
> d_instantiate(dentry, inode);

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