On 11/7/2023 5:40 AM, Roberto Sassu wrote: > From: Roberto Sassu <[email protected]> > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce > the path_post_mknod hook. > > IMA-appraisal requires all existing files in policy to have a file > hash/signature stored in security.ima. An exception is made for empty files > created by mknod, by tagging them as new files. > > LSMs could also take some action after files are created. > > The new hook cannot return an error and cannot cause the operation to be > reverted. > > Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Casey Schaufler <[email protected]> > --- > fs/namei.c | 5 +++++ > include/linux/lsm_hook_defs.h | 2 ++ > include/linux/security.h | 5 +++++ > security/security.c | 14 ++++++++++++++ > 4 files changed, 26 insertions(+) > > diff --git a/fs/namei.c b/fs/namei.c > index fb93d3e13df6..b7f433720b1e 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -4047,6 +4047,11 @@ static int do_mknodat(int dfd, struct filename *name, > umode_t mode, > dentry, mode, 0); > break; > } > + > + if (error) > + goto out2; > + > + security_path_post_mknod(idmap, dentry); > out2: > done_path_create(&path, dentry); > if (retry_estale(error, lookup_flags)) { > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > index 5d0a09ead7ac..e491951399f7 100644 > --- a/include/linux/lsm_hook_defs.h > +++ b/include/linux/lsm_hook_defs.h > @@ -94,6 +94,8 @@ LSM_HOOK(int, 0, path_mkdir, const struct path *dir, struct > dentry *dentry, > LSM_HOOK(int, 0, path_rmdir, const struct path *dir, struct dentry *dentry) > LSM_HOOK(int, 0, path_mknod, const struct path *dir, struct dentry *dentry, > umode_t mode, unsigned int dev) > +LSM_HOOK(void, LSM_RET_VOID, path_post_mknod, struct mnt_idmap *idmap, > + struct dentry *dentry) > LSM_HOOK(int, 0, path_truncate, const struct path *path) > LSM_HOOK(int, 0, path_symlink, const struct path *dir, struct dentry *dentry, > const char *old_name) > diff --git a/include/linux/security.h b/include/linux/security.h > index a570213693d9..68cbdc84506e 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -1884,6 +1884,7 @@ int security_path_mkdir(const struct path *dir, struct > dentry *dentry, umode_t m > int security_path_rmdir(const struct path *dir, struct dentry *dentry); > int security_path_mknod(const struct path *dir, struct dentry *dentry, > umode_t mode, > unsigned int dev); > +void security_path_post_mknod(struct mnt_idmap *idmap, struct dentry > *dentry); > int security_path_truncate(const struct path *path); > int security_path_symlink(const struct path *dir, struct dentry *dentry, > const char *old_name); > @@ -1918,6 +1919,10 @@ static inline int security_path_mknod(const struct > path *dir, struct dentry *den > return 0; > } > > +static inline void security_path_post_mknod(struct mnt_idmap *idmap, > + struct dentry *dentry) > +{ } > + > static inline int security_path_truncate(const struct path *path) > { > return 0; > diff --git a/security/security.c b/security/security.c > index 331a3e5efb62..5eaf5f2aa5ea 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -1800,6 +1800,20 @@ int security_path_mknod(const struct path *dir, struct > dentry *dentry, > } > EXPORT_SYMBOL(security_path_mknod); > > +/** > + * security_path_post_mknod() - Update inode security field after file > creation > + * @idmap: idmap of the mount > + * @dentry: new file > + * > + * Update inode security field after a file has been created. > + */ > +void security_path_post_mknod(struct mnt_idmap *idmap, struct dentry *dentry) > +{ > + if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) > + return; > + call_void_hook(path_post_mknod, idmap, dentry); > +} > + > /** > * security_path_mkdir() - Check if creating a new directory is allowed > * @dir: parent directory
