On Mon, 2021-10-04 at 08:54 -0700, Casey Schaufler wrote: > On 10/4/2021 8:20 AM, Jeff Layton wrote: > > On Thu, 2021-09-30 at 14:59 -0400, Vivek Goyal wrote: > > > Right now security_dentry_init_security() only supports single security > > > label and is used by SELinux only. There are two users of of this hook, > > > namely ceph and nfs. > > > > > > NFS does not care about xattr name. Ceph hardcodes the xattr name to > > > security.selinux (XATTR_NAME_SELINUX). > > > > > > I am making changes to fuse/virtiofs to send security label to virtiofsd > > > and I need to send xattr name as well. I also hardcoded the name of > > > xattr to security.selinux. > > > > > > Stephen Smalley suggested that it probably is a good idea to modify > > > security_dentry_init_security() to also return name of xattr so that > > > we can avoid this hardcoding in the callers. > > > > > > This patch adds a new parameter "const char **xattr_name" to > > > security_dentry_init_security() and LSM puts the name of xattr > > > too if caller asked for it (xattr_name != NULL). > > > > > > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx> > > > --- > > > > > > I have compile tested this patch. Don't know how to setup ceph and > > > test it. Its a very simple change. Hopefully ceph developers can > > > have a quick look at it. > > > > > > A similar attempt was made three years back. > > > > > > https://lore.kernel.org/linux-security-module/20180626080429.27304-1-zyan@xxxxxxxxxx/T/ > > > --- > > > fs/ceph/xattr.c | 3 +-- > > > fs/nfs/nfs4proc.c | 3 ++- > > > include/linux/lsm_hook_defs.h | 3 ++- > > > include/linux/lsm_hooks.h | 1 + > > > include/linux/security.h | 6 ++++-- > > > security/security.c | 7 ++++--- > > > security/selinux/hooks.c | 6 +++++- > > > 7 files changed, 19 insertions(+), 10 deletions(-) > > > > > > Index: redhat-linux/security/selinux/hooks.c > > > =================================================================== > > > --- redhat-linux.orig/security/selinux/hooks.c 2021-09-28 11:36:03.559785943 -0400 > > > +++ redhat-linux/security/selinux/hooks.c 2021-09-30 14:01:05.869195347 -0400 > > > @@ -2948,7 +2948,8 @@ static void selinux_inode_free_security( > > > } > > > > > I agree with Al that it would be cleaner to just return the string, but > > the call_*_hook stuff makes that a bit more tricky. I suppose this is a > > reasonable compromise. > > call_int_hook() and call_void_hook() were introduced to reduce the monotonous > repetition in the source. They are cosmetic and add no real value. They shouldn't > be a consideration in the discussion. > > There is a problem with Al's suggestion. The interface as used today has two real > problems. It returns an attribute value without identifying the attribute. Al's > interface would address this issue. The other problem is that the interface can't > provide multiple attribute+value pairs. The interface is going to need changed to > support that for full module stacking. I don't see a rational way to extend the > interface if it returns a string when there are multiple attributes to choose from. > Is that also a problem for the ctx parameter? In the case of full module stacking do you get back multiple contexts as well? > > > static int selinux_dentry_init_security(struct dentry *dentry, int mode, > > > - const struct qstr *name, void **ctx, > > > + const struct qstr *name, > > > + const char **xattr_name, void **ctx, > > > u32 *ctxlen) > > > { > > > u32 newsid; > > > @@ -2961,6 +2962,9 @@ static int selinux_dentry_init_security( > > > if (rc) > > > return rc; > > > > > > + if (xattr_name) > > > + *xattr_name = XATTR_NAME_SELINUX; > > > + > > > return security_sid_to_context(&selinux_state, newsid, (char **)ctx, > > > ctxlen); > > > } > > > Index: redhat-linux/security/security.c > > > =================================================================== > > > --- redhat-linux.orig/security/security.c 2021-08-16 10:39:28.518988836 -0400 > > > +++ redhat-linux/security/security.c 2021-09-30 13:54:36.367195347 -0400 > > > @@ -1052,11 +1052,12 @@ void security_inode_free(struct inode *i > > > } > > > > > > int security_dentry_init_security(struct dentry *dentry, int mode, > > > - const struct qstr *name, void **ctx, > > > - u32 *ctxlen) > > > + const struct qstr *name, > > > + const char **xattr_name, void **ctx, > > > + u32 *ctxlen) > > > { > > > return call_int_hook(dentry_init_security, -EOPNOTSUPP, dentry, mode, > > > - name, ctx, ctxlen); > > > + name, xattr_name, ctx, ctxlen); > > > } > > > EXPORT_SYMBOL(security_dentry_init_security); > > > > > > Index: redhat-linux/include/linux/lsm_hooks.h > > > =================================================================== > > > --- redhat-linux.orig/include/linux/lsm_hooks.h 2021-06-02 10:20:27.717485143 -0400 > > > +++ redhat-linux/include/linux/lsm_hooks.h 2021-09-30 13:56:48.440195347 -0400 > > > @@ -196,6 +196,7 @@ > > > * @dentry dentry to use in calculating the context. > > > * @mode mode used to determine resource type. > > > * @name name of the last path component used to create file > > > + * @xattr_name pointer to place the pointer to security xattr name > > It might be a good idea to also document the lifetime for xattr_name > > here. In particular you're returning a pointer to a static string, and > > it would be good to note that the caller needn't free it or anything. > > > > > * @ctx pointer to place the pointer to the resulting context in. > > > * @ctxlen point to place the length of the resulting context. > > > * @dentry_create_files_as: > > > Index: redhat-linux/include/linux/security.h > > > =================================================================== > > > --- redhat-linux.orig/include/linux/security.h 2021-08-16 10:39:28.484988836 -0400 > > > +++ redhat-linux/include/linux/security.h 2021-09-30 13:59:00.288195347 -0400 > > > @@ -317,8 +317,9 @@ int security_add_mnt_opt(const char *opt > > > int len, void **mnt_opts); > > > int security_move_mount(const struct path *from_path, const struct path *to_path); > > > int security_dentry_init_security(struct dentry *dentry, int mode, > > > - const struct qstr *name, void **ctx, > > > - u32 *ctxlen); > > > + const struct qstr *name, > > > + const char **xattr_name, void **ctx, > > > + u32 *ctxlen); > > > int security_dentry_create_files_as(struct dentry *dentry, int mode, > > > struct qstr *name, > > > const struct cred *old, > > > @@ -739,6 +740,7 @@ static inline void security_inode_free(s > > > static inline int security_dentry_init_security(struct dentry *dentry, > > > int mode, > > > const struct qstr *name, > > > + const char **xattr_name, > > > void **ctx, > > > u32 *ctxlen) > > > { > > > Index: redhat-linux/include/linux/lsm_hook_defs.h > > > =================================================================== > > > --- redhat-linux.orig/include/linux/lsm_hook_defs.h 2021-07-07 11:54:59.673549151 -0400 > > > +++ redhat-linux/include/linux/lsm_hook_defs.h 2021-09-30 14:02:13.114195347 -0400 > > > @@ -83,7 +83,8 @@ LSM_HOOK(int, 0, sb_add_mnt_opt, const c > > > LSM_HOOK(int, 0, move_mount, const struct path *from_path, > > > const struct path *to_path) > > > LSM_HOOK(int, 0, dentry_init_security, struct dentry *dentry, > > > - int mode, const struct qstr *name, void **ctx, u32 *ctxlen) > > > + int mode, const struct qstr *name, const char **xattr_name, > > > + void **ctx, u32 *ctxlen) > > > LSM_HOOK(int, 0, dentry_create_files_as, struct dentry *dentry, int mode, > > > struct qstr *name, const struct cred *old, struct cred *new) > > > > > > Index: redhat-linux/fs/nfs/nfs4proc.c > > > =================================================================== > > > --- redhat-linux.orig/fs/nfs/nfs4proc.c 2021-07-14 14:47:42.732842926 -0400 > > > +++ redhat-linux/fs/nfs/nfs4proc.c 2021-09-30 14:06:02.249195347 -0400 > > > @@ -127,7 +127,8 @@ nfs4_label_init_security(struct inode *d > > > return NULL; > > > > > > err = security_dentry_init_security(dentry, sattr->ia_mode, > > > - &dentry->d_name, (void **)&label->label, &label->len); > > > + &dentry->d_name, NULL, > > > + (void **)&label->label, &label->len); > > > if (err == 0) > > > return label; > > > > > > Index: redhat-linux/fs/ceph/xattr.c > > > =================================================================== > > > --- redhat-linux.orig/fs/ceph/xattr.c 2021-09-09 13:05:21.800611264 -0400 > > > +++ redhat-linux/fs/ceph/xattr.c 2021-09-30 14:14:59.892195347 -0400 > > > @@ -1311,7 +1311,7 @@ int ceph_security_init_secctx(struct den > > > int err; > > > > > > err = security_dentry_init_security(dentry, mode, &dentry->d_name, > > > - &as_ctx->sec_ctx, > > > + &name, &as_ctx->sec_ctx, > > > &as_ctx->sec_ctxlen); > > > if (err < 0) { > > > WARN_ON_ONCE(err != -EOPNOTSUPP); > > > @@ -1335,7 +1335,6 @@ int ceph_security_init_secctx(struct den > > > * It only supports single security module and only selinux has > > > * dentry_init_security hook. > > > */ > > > - name = XATTR_NAME_SELINUX; > > > name_len = strlen(name); > > > err = ceph_pagelist_reserve(pagelist, > > > 4 * 2 + name_len + as_ctx->sec_ctxlen); > > > > > Looks reasonable overall. > > > > Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> > > > -- Jeff Layton <jlayton@xxxxxxxxxx>
