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security: Introduce inode_post_create_tmpfile hook

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In preparation for moving IMA and EVM to the LSM infrastructure, introduce
the inode_post_create_tmpfile hook.

As temp files can be made persistent, treat new temp files like other new
files, so that the file hash is calculated and stored in the security
xattr.

LSMs could also take some action after temp files have been created.

The new hook cannot return an error and cannot cause the operation to be
canceled.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Roberto Sassu 2024-02-15 11:31:03 +01:00 committed by Paul Moore
parent 08abce60d6
commit a7811e34d1
4 changed files with 24 additions and 0 deletions
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1
fs/namei.c
View file

@ -3705,6 +3705,7 @@ static int vfs_tmpfile(struct mnt_idmap *idmap,
inode->i_state |= I_LINKABLE;
spin_unlock(&inode->i_lock);
}
security_inode_post_create_tmpfile(idmap, inode);
ima_post_create_tmpfile(idmap, inode);
return 0;
}

2
include/linux/lsm_hook_defs.h
View file

@ -121,6 +121,8 @@ LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode,
const struct qstr *name, const struct inode *context_inode)
LSM_HOOK(int, 0, inode_create, struct inode *dir, struct dentry *dentry,
umode_t mode)
LSM_HOOK(void, LSM_RET_VOID, inode_post_create_tmpfile, struct mnt_idmap *idmap,
struct inode *inode)
LSM_HOOK(int, 0, inode_link, struct dentry *old_dentry, struct inode *dir,
struct dentry *new_dentry)
LSM_HOOK(int, 0, inode_unlink, struct inode *dir, struct dentry *dentry)

6
include/linux/security.h
View file

@ -344,6 +344,8 @@ int security_inode_init_security_anon(struct inode *inode,
const struct qstr *name,
const struct inode *context_inode);
int security_inode_create(struct inode *dir, struct dentry *dentry, umode_t mode);
void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
struct inode *inode);
int security_inode_link(struct dentry *old_dentry, struct inode *dir,
struct dentry *new_dentry);
int security_inode_unlink(struct inode *dir, struct dentry *dentry);
@ -811,6 +813,10 @@ static inline int security_inode_create(struct inode *dir,
return 0;
}
static inline void
security_inode_post_create_tmpfile(struct mnt_idmap *idmap, struct inode *inode)
{ }
static inline int security_inode_link(struct dentry *old_dentry,
struct inode *dir,
struct dentry *new_dentry)

15
security/security.c
View file

@ -2013,6 +2013,21 @@ int security_inode_create(struct inode *dir, struct dentry *dentry,
}
EXPORT_SYMBOL_GPL(security_inode_create);
/**
* security_inode_post_create_tmpfile() - Update inode security of new tmpfile
* @idmap: idmap of the mount
* @inode: inode of the new tmpfile
*
* Update inode security data after a tmpfile has been created.
*/
void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
struct inode *inode)
{
if (unlikely(IS_PRIVATE(inode)))
return;
call_void_hook(inode_post_create_tmpfile, idmap, inode);
}
/**
* security_inode_link() - Check if creating a hard link is allowed
* @old_dentry: existing file