On Tue, Oct 12, 2021 at 11:24:23AM -0700, Casey Schaufler wrote: > On 10/12/2021 11:06 AM, Vivek Goyal wrote: > > When a new inode is created, send its security context to server along > > with creation request (FUSE_CREAT, FUSE_MKNOD, FUSE_MKDIR and FUSE_SYMLINK). > > This gives server an opportunity to create new file and set security > > context (possibly atomically). In all the configurations it might not > > be possible to set context atomically. > > > > Like nfs and ceph, use security_dentry_init_security() to dermine security > > context of inode and send it with create, mkdir, mknod, and symlink requests. > > > > Following is the information sent to server. > > > > - struct fuse_secctxs. > > This contains total number of security contexts being sent. > > > > - struct fuse_secctx. > > This contains total size of security context which follows this structure. > > There is one fuse_secctx instance per security context. > > > > - xattr name string. > > This string represents name of xattr which should be used while setting > > security context. As of now it is hardcoded to "security.selinux". > > Where is the name hardcoded? I looks as if you're getting the attribute > name along with the value from security_dentry_init_security(). Sorry, I copied pasted this description from V1 where I was hardcoding the name to "security.selinux". But V2 got rid of that hardcoding and that's why this patch series is dependent on the other patch which modifies security_dentry_init_security() signature. https://lore.kernel.org/linux-fsdevel/YWWMO%2FZDrvDZ5X4c@xxxxxxxxxx/ Thanks Vivek > > > > > - security context. > > This is the actual security context whose size is specified in fuse_secctx > > struct. > > > > This patch is modified version of patch from > > Chirantan Ekbote <chirantan@xxxxxxxxxxxx> > > > > v2: > > - Added "fuse_secctxs" structure where one can specify how many security > > contexts are being sent. This can be useful down the line if we > > have more than one security contexts being set. > > > > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx> > > --- > > fs/fuse/dir.c | 115 ++++++++++++++++++++++++++++++++++++-- > > fs/fuse/fuse_i.h | 3 + > > fs/fuse/inode.c | 4 +- > > include/uapi/linux/fuse.h | 20 +++++++ > > 4 files changed, 136 insertions(+), 6 deletions(-) > > > > diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c > > index d9b977c0f38d..ce62593a61f9 100644 > > --- a/fs/fuse/dir.c > > +++ b/fs/fuse/dir.c > > @@ -17,6 +17,9 @@ > > #include <linux/xattr.h> > > #include <linux/iversion.h> > > #include <linux/posix_acl.h> > > +#include <linux/security.h> > > +#include <linux/types.h> > > +#include <linux/kernel.h> > > > > static void fuse_advise_use_readdirplus(struct inode *dir) > > { > > @@ -456,6 +459,66 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry, > > return ERR_PTR(err); > > } > > > > +static int get_security_context(struct dentry *entry, umode_t mode, > > + void **security_ctx, u32 *security_ctxlen) > > +{ > > + struct fuse_secctx *fsecctx; > > + struct fuse_secctxs *fsecctxs; > > + void *ctx, *full_ctx; > > + u32 ctxlen, full_ctxlen; > > + int err = 0; > > + const char *name; > > + > > + err = security_dentry_init_security(entry, mode, &entry->d_name, > > + &name, &ctx, &ctxlen); > > + if (err) { > > + if (err != -EOPNOTSUPP) > > + goto out_err; > > + /* No LSM is supporting this security hook. Ignore error */ > > + err = 0; > > + ctxlen = 0; > > + } > > + > > + if (ctxlen > 0) { > > + void *ptr; > > + > > + full_ctxlen = sizeof(*fsecctxs) + sizeof(*fsecctx) + > > + strlen(name) + ctxlen + 1; > > + full_ctx = kzalloc(full_ctxlen, GFP_KERNEL); > > + if (!full_ctx) { > > + err = -ENOMEM; > > + kfree(ctx); > > + goto out_err; > > + } > > + > > + ptr = full_ctx; > > + fsecctxs = (struct fuse_secctxs*) ptr; > > + fsecctxs->nr_secctx = 1; > > + ptr += sizeof(*fsecctxs); > > + > > + fsecctx = (struct fuse_secctx*) ptr; > > + fsecctx->size = ctxlen; > > + ptr += sizeof(*fsecctx); > > + > > + strcpy(ptr, name); > > + ptr += strlen(name) + 1; > > + memcpy(ptr, ctx, ctxlen); > > + kfree(ctx); > > + } else { > > + full_ctxlen = sizeof(*fsecctxs); > > + full_ctx = kzalloc(full_ctxlen, GFP_KERNEL); > > + if (!full_ctx) { > > + err = -ENOMEM; > > + goto out_err; > > + } > > + } > > + > > + *security_ctxlen = full_ctxlen; > > + *security_ctx = full_ctx; > > +out_err: > > + return err; > > +} > > + > > /* > > * Atomic create+open operation > > * > > @@ -476,6 +539,8 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, > > struct fuse_entry_out outentry; > > struct fuse_inode *fi; > > struct fuse_file *ff; > > + void *security_ctx = NULL; > > + u32 security_ctxlen; > > > > /* Userspace expects S_IFREG in create mode */ > > BUG_ON((mode & S_IFMT) != S_IFREG); > > @@ -517,6 +582,18 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, > > args.out_args[0].value = &outentry; > > args.out_args[1].size = sizeof(outopen); > > args.out_args[1].value = &outopen; > > + > > + if (fm->fc->init_security) { > > + err = get_security_context(entry, mode, &security_ctx, > > + &security_ctxlen); > > + if (err) > > + goto out_put_forget_req; > > + > > + args.in_numargs = 3; > > + args.in_args[2].size = security_ctxlen; > > + args.in_args[2].value = security_ctx; > > + } > > + > > err = fuse_simple_request(fm, &args); > > if (err) > > goto out_free_ff; > > @@ -554,6 +631,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, > > > > out_free_ff: > > fuse_file_free(ff); > > + kfree(security_ctx); > > out_put_forget_req: > > kfree(forget); > > out_err: > > @@ -613,13 +691,15 @@ static int fuse_atomic_open(struct inode *dir, struct dentry *entry, > > */ > > static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args, > > struct inode *dir, struct dentry *entry, > > - umode_t mode) > > + umode_t mode, bool init_security) > > { > > struct fuse_entry_out outarg; > > struct inode *inode; > > struct dentry *d; > > int err; > > struct fuse_forget_link *forget; > > + void *security_ctx = NULL; > > + u32 security_ctxlen = 0; > > > > if (fuse_is_bad(dir)) > > return -EIO; > > @@ -633,7 +713,29 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args, > > args->out_numargs = 1; > > args->out_args[0].size = sizeof(outarg); > > args->out_args[0].value = &outarg; > > + > > + if (init_security) { > > + unsigned short idx = args->in_numargs; > > + > > + if ((size_t)idx >= ARRAY_SIZE(args->in_args)) { > > + err = -ENOMEM; > > + goto out_put_forget_req; > > + } > > + > > + err = get_security_context(entry, mode, &security_ctx, > > + &security_ctxlen); > > + if (err) > > + goto out_put_forget_req; > > + > > + if (security_ctxlen > 0) { > > + args->in_args[idx].size = security_ctxlen; > > + args->in_args[idx].value = security_ctx; > > + args->in_numargs++; > > + } > > + } > > + > > err = fuse_simple_request(fm, args); > > + kfree(security_ctx); > > if (err) > > goto out_put_forget_req; > > > > @@ -691,7 +793,7 @@ static int fuse_mknod(struct user_namespace *mnt_userns, struct inode *dir, > > args.in_args[0].value = &inarg; > > args.in_args[1].size = entry->d_name.len + 1; > > args.in_args[1].value = entry->d_name.name; > > - return create_new_entry(fm, &args, dir, entry, mode); > > + return create_new_entry(fm, &args, dir, entry, mode, fm->fc->init_security); > > } > > > > static int fuse_create(struct user_namespace *mnt_userns, struct inode *dir, > > @@ -719,7 +821,8 @@ static int fuse_mkdir(struct user_namespace *mnt_userns, struct inode *dir, > > args.in_args[0].value = &inarg; > > args.in_args[1].size = entry->d_name.len + 1; > > args.in_args[1].value = entry->d_name.name; > > - return create_new_entry(fm, &args, dir, entry, S_IFDIR); > > + return create_new_entry(fm, &args, dir, entry, S_IFDIR, > > + fm->fc->init_security); > > } > > > > static int fuse_symlink(struct user_namespace *mnt_userns, struct inode *dir, > > @@ -735,7 +838,8 @@ static int fuse_symlink(struct user_namespace *mnt_userns, struct inode *dir, > > args.in_args[0].value = entry->d_name.name; > > args.in_args[1].size = len; > > args.in_args[1].value = link; > > - return create_new_entry(fm, &args, dir, entry, S_IFLNK); > > + return create_new_entry(fm, &args, dir, entry, S_IFLNK, > > + fm->fc->init_security); > > } > > > > void fuse_update_ctime(struct inode *inode) > > @@ -915,7 +1019,8 @@ static int fuse_link(struct dentry *entry, struct inode *newdir, > > args.in_args[0].value = &inarg; > > args.in_args[1].size = newent->d_name.len + 1; > > args.in_args[1].value = newent->d_name.name; > > - err = create_new_entry(fm, &args, newdir, newent, inode->i_mode); > > + err = create_new_entry(fm, &args, newdir, newent, inode->i_mode, > > + false); > > /* Contrary to "normal" filesystems it can happen that link > > makes two "logical" inodes point to the same "physical" > > inode. We invalidate the attributes of the old one, so it > > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h > > index 319596df5dc6..885f34f9967f 100644 > > --- a/fs/fuse/fuse_i.h > > +++ b/fs/fuse/fuse_i.h > > @@ -765,6 +765,9 @@ struct fuse_conn { > > /* Propagate syncfs() to server */ > > unsigned int sync_fs:1; > > > > + /* Initialize security xattrs when creating a new inode */ > > + unsigned int init_security:1; > > + > > /** The number of requests waiting for completion */ > > atomic_t num_waiting; > > > > diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c > > index 36cd03114b6d..343bc9cfbd92 100644 > > --- a/fs/fuse/inode.c > > +++ b/fs/fuse/inode.c > > @@ -1152,6 +1152,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args, > > } > > if (arg->flags & FUSE_SETXATTR_EXT) > > fc->setxattr_ext = 1; > > + if (arg->flags & FUSE_SECURITY_CTX) > > + fc->init_security = 1; > > } else { > > ra_pages = fc->max_read / PAGE_SIZE; > > fc->no_lock = 1; > > @@ -1195,7 +1197,7 @@ void fuse_send_init(struct fuse_mount *fm) > > FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL | > > FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS | > > FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA | > > - FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT; > > + FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_SECURITY_CTX; > > #ifdef CONFIG_FUSE_DAX > > if (fm->fc->dax) > > ia->in.flags |= FUSE_MAP_ALIGNMENT; > > diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h > > index 2fe54c80051a..b31a0f79fde8 100644 > > --- a/include/uapi/linux/fuse.h > > +++ b/include/uapi/linux/fuse.h > > @@ -986,4 +986,24 @@ struct fuse_syncfs_in { > > uint64_t padding; > > }; > > > > +/* > > + * For each security context, send fuse_secctx with size of security context > > + * fuse_secctx will be followed by security context name and this in turn > > + * will be followed by actual context label. > > + * fuse_secctx, name, context > > + * */ > > +struct fuse_secctx { > > + uint32_t size; > > + uint32_t padding; > > +}; > > + > > +/* > > + * Contains the information about how many fuse_secctx structures are being > > + * sent. > > + */ > > +struct fuse_secctxs { > > + uint32_t nr_secctx; > > + uint32_t padding; > > +}; > > + > > #endif /* _LINUX_FUSE_H */ >
