fuse: optional supplementary group in create requests

Permission to create an object (create, mkdir, symlink, mknod) needs to
take supplementary groups into account.

Add a supplementary group request extension.  This can contain an arbitrary
number of group IDs and can be added to any request.  This extension is not
added to any request by default.

Add FUSE_CREATE_SUPP_GROUP init flag to enable supplementary group info in
creation requests.  This adds just a single supplementary group that
matches the parent group in the case described above.  In other cases the
extension is not added.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index fa6381f199b342762a453144c63b255de584171d..0c1d7e387f0d5faf887ccdc86d221658ca38a556 100644 (file)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -521,7 +521,63 @@ out_err:
        return err;
 }
 
-static int get_create_ext(struct fuse_args *args, struct dentry *dentry,
+static void *extend_arg(struct fuse_in_arg *buf, u32 bytes)
+{
+       void *p;
+       u32 newlen = buf->size + bytes;
+
+       p = krealloc(buf->value, newlen, GFP_KERNEL);
+       if (!p) {
+               kfree(buf->value);
+               buf->size = 0;
+               buf->value = NULL;
+               return NULL;
+       }
+
+       memset(p + buf->size, 0, bytes);
+       buf->value = p;
+       buf->size = newlen;
+
+       return p + newlen - bytes;
+}
+
+static u32 fuse_ext_size(size_t size)
+{
+       return FUSE_REC_ALIGN(sizeof(struct fuse_ext_header) + size);
+}
+
+/*
+ * This adds just a single supplementary group that matches the parent's group.
+ */
+static int get_create_supp_group(struct inode *dir, struct fuse_in_arg *ext)
+{
+       struct fuse_conn *fc = get_fuse_conn(dir);
+       struct fuse_ext_header *xh;
+       struct fuse_supp_groups *sg;
+       kgid_t kgid = dir->i_gid;
+       gid_t parent_gid = from_kgid(fc->user_ns, kgid);
+       u32 sg_len = fuse_ext_size(sizeof(*sg) + sizeof(sg->groups[0]));
+
+       if (parent_gid == (gid_t) -1 || gid_eq(kgid, current_fsgid()) ||
+           !in_group_p(kgid))
+               return 0;
+
+       xh = extend_arg(ext, sg_len);
+       if (!xh)
+               return -ENOMEM;
+
+       xh->size = sg_len;
+       xh->type = FUSE_EXT_GROUPS;
+
+       sg = (struct fuse_supp_groups *) &xh[1];
+       sg->nr_groups = 1;
+       sg->groups[0] = parent_gid;
+
+       return 0;
+}
+
+static int get_create_ext(struct fuse_args *args,
+                         struct inode *dir, struct dentry *dentry,
                          umode_t mode)
 {
        struct fuse_conn *fc = get_fuse_conn_super(dentry->d_sb);
@@ -530,6 +586,8 @@ static int get_create_ext(struct fuse_args *args, struct dentry *dentry,
 
        if (fc->init_security)
                err = get_security_context(dentry, mode, &ext);
+       if (!err && fc->create_supp_group)
+               err = get_create_supp_group(dir, &ext);
 
        if (!err && ext.size) {
                WARN_ON(args->in_numargs >= ARRAY_SIZE(args->in_args));
@@ -612,7 +670,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
        args.out_args[1].size = sizeof(outopen);
        args.out_args[1].value = &outopen;
 
-       err = get_create_ext(&args, entry, mode);
+       err = get_create_ext(&args, dir, entry, mode);
        if (err)
                goto out_put_forget_req;
 
@@ -739,7 +797,7 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args,
        args->out_args[0].value = &outarg;
 
        if (args->opcode != FUSE_LINK) {
-               err = get_create_ext(args, entry, mode);
+               err = get_create_ext(args, dir, entry, mode);
                if (err)
                        goto out_put_forget_req;
        }

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index ac300f14aa2dd4a98a113bb0b6efb599f38d526a..e13a8eff2e3de55198447dd0035435e87d18ce2c 100644 (file)
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -783,6 +783,9 @@ struct fuse_conn {
        /* Initialize security xattrs when creating a new inode */
        unsigned int init_security:1;
 
+       /* Add supplementary group info when creating a new inode */
+       unsigned int create_supp_group:1;
+
        /* Does the filesystem support per inode DAX? */
        unsigned int inode_dax:1;
 

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 6b3beda16c1ba0a4394d30db7671edd73f2cc034..114bdb3f7ccb68aa6820b603261fae5548b81bff 100644 (file)
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1201,6 +1201,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
                                fc->setxattr_ext = 1;
                        if (flags & FUSE_SECURITY_CTX)
                                fc->init_security = 1;
+                       if (flags & FUSE_CREATE_SUPP_GROUP)
+                               fc->create_supp_group = 1;
                } else {
                        ra_pages = fc->max_read / PAGE_SIZE;
                        fc->no_lock = 1;
@@ -1246,7 +1248,7 @@ void fuse_send_init(struct fuse_mount *fm)
                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_INIT_EXT |
-               FUSE_SECURITY_CTX;
+               FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP;
 #ifdef CONFIG_FUSE_DAX
        if (fm->fc->dax)
                flags |= FUSE_MAP_ALIGNMENT;

diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index c71f12429e3d9dc5409d139a9e9eba77ab363866..1b9d0dfae72df6df7ac4defb1aed14ccb77f2670 100644 (file)
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -204,6 +204,8 @@
  *  - add total_extlen to fuse_in_header
  *  - add FUSE_MAX_NR_SECCTX
  *  - add extension header
+ *  - add FUSE_EXT_GROUPS
+ *  - add FUSE_CREATE_SUPP_GROUP
  */
 
 #ifndef _LINUX_FUSE_H
@@ -365,6 +367,8 @@ struct fuse_file_lock {
  * FUSE_SECURITY_CTX:  add security context to create, mkdir, symlink, and
  *                     mknod
  * FUSE_HAS_INODE_DAX:  use per inode DAX
+ * FUSE_CREATE_SUPP_GROUP: add supplementary group info to create, mkdir,
+ *                     symlink and mknod (single group that matches parent)
  */
 #define FUSE_ASYNC_READ                (1 << 0)
 #define FUSE_POSIX_LOCKS       (1 << 1)
@@ -401,6 +405,7 @@ struct fuse_file_lock {
 /* bits 32..63 get shifted down 32 bits into the flags2 field */
 #define FUSE_SECURITY_CTX      (1ULL << 32)
 #define FUSE_HAS_INODE_DAX     (1ULL << 33)
+#define FUSE_CREATE_SUPP_GROUP (1ULL << 34)
 
 /**
  * CUSE INIT request/reply flags
@@ -509,10 +514,12 @@ struct fuse_file_lock {
 /**
  * extension type
  * FUSE_MAX_NR_SECCTX: maximum value of &fuse_secctx_header.nr_secctx
+ * FUSE_EXT_GROUPS: &fuse_supp_groups extension
  */
 enum fuse_ext_type {
        /* Types 0..31 are reserved for fuse_secctx_header */
        FUSE_MAX_NR_SECCTX      = 31,
+       FUSE_EXT_GROUPS         = 32,
 };
 
 enum fuse_opcode {
@@ -1073,4 +1080,14 @@ struct fuse_ext_header {
        uint32_t        type;
 };
 
+/**
+ * struct fuse_supp_groups - Supplementary group extension
+ * @nr_groups: number of supplementary groups
+ * @groups: flexible array of group IDs
+ */
+struct fuse_supp_groups {
+       uint32_t        nr_groups;
+       uint32_t        groups[];
+};
+
 #endif /* _LINUX_FUSE_H */