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commit 49dcce14db81499c84f741125d80cb6638f0ee28 Author: Marco Casaroli <[email protected]> AuthorDate: Mon Oct 19 01:57:03 2026 +0200 fs/v9fs: Give a new file the effective user and group of the caller. The server gives a new file the user of the fid that creates it. V9FS attached only once, at mount time, so every file, directory and symbolic link belonged to the user that mounted the file system. The create requests also sent the real group ID, not the effective group ID. With CONFIG_SCHED_USER_IDENTITY, attach again for each effective user ID that uses the mount, and start each walk from the root fid of the caller. Send the effective group ID in Tlcreate, Tmkdir and Tsymlink. Without CONFIG_SCHED_USER_IDENTITY, the IDs are 0 as before. With QEMU security_model=mapped-xattr, a file that a task with the effective user ID 1000 creates now shows uid 1000 in stat(). Assisted-by: Claude Code:claude-opus-5-5 Signed-off-by: Marco Casaroli <[email protected]> --- fs/v9fs/client.c | 153 +++++++++++++++++++++++++++++++++++++++++++++++++------ fs/v9fs/client.h | 15 ++++++ 2 files changed, 152 insertions(+), 16 deletions(-) diff --git a/fs/v9fs/client.c b/fs/v9fs/client.c index 2f10a78f593..aae85210aea 100644 --- a/fs/v9fs/client.c +++ b/fs/v9fs/client.c @@ -691,7 +691,8 @@ static int v9fs_client_clunk(FAR struct v9fs_client_s *client, ****************************************************************************/ static int v9fs_client_attach(FAR struct v9fs_client_s *client, uint32_t fid, - FAR const char *uname, FAR const char *aname) + FAR const char *uname, FAR const char *aname, + uint32_t uid) { struct v9fs_attach_s request; struct v9fs_rattach_s response; @@ -699,7 +700,6 @@ static int v9fs_client_attach(FAR struct v9fs_client_s *client, uint32_t fid, struct iovec riov[1]; uint16_t uname_len = strlen(uname); uint16_t aname_len = strlen(aname); - uint32_t uid = getuid(); off_t offset = 0; uint32_t newfid; int ret; @@ -798,6 +798,86 @@ static int v9fs_client_version(FAR struct v9fs_client_s *client) return 0; } +/**************************************************************************** + * v9fs_client_root + * + * Description: + * Return the root fid of the effective user of the caller. The server + * gives new files the user of the fid that creates them, so each user + * attaches with its own uid when it first uses the mount. + * + ****************************************************************************/ + +static int v9fs_client_root(FAR struct v9fs_client_s *client) +{ +#ifdef CONFIG_SCHED_USER_IDENTITY + FAR struct v9fs_root_s *root; + FAR struct v9fs_root_s *entry; + uid_t uid = geteuid(); + int ret; + + if (uid == client->root_uid) + { + return client->root_fid; + } + + nxmutex_lock(&client->lock); + for (root = client->roots; root != NULL; root = root->next) + { + if (root->uid == uid) + { + nxmutex_unlock(&client->lock); + return root->fid; + } + } + + nxmutex_unlock(&client->lock); + + entry = fs_heap_malloc(sizeof(struct v9fs_root_s)); + if (entry == NULL) + { + return -ENOMEM; + } + + ret = v9fs_client_attach(client, V9FS_NOFID, client->uname, + client->aname, uid); + if (ret < 0) + { + fs_heap_free(entry); + return ret; + } + + entry->uid = uid; + entry->fid = ret; + + /* Another thread of the same user can attach at the same time */ + + nxmutex_lock(&client->lock); + for (root = client->roots; root != NULL; root = root->next) + { + if (root->uid == uid) + { + break; + } + } + + if (root == NULL) + { + entry->next = client->roots; + client->roots = entry; + nxmutex_unlock(&client->lock); + return entry->fid; + } + + nxmutex_unlock(&client->lock); + v9fs_client_clunk(client, entry->fid); + fs_heap_free(entry); + return root->fid; +#else + return client->root_fid; +#endif +} + /**************************************************************************** * Public Functions ****************************************************************************/ @@ -1382,7 +1462,7 @@ int v9fs_client_mkdir(FAR struct v9fs_client_s *client, uint32_t fid, struct v9fs_rmkdir_s response; struct iovec wiov[1]; struct iovec riov[1]; - uint32_t gid = getgid(); + uint32_t gid = getegid(); off_t offset = 0; /* size[4] Tmkdir tag[2] dfid[4] name[s] mode[4] gid[4] @@ -1424,7 +1504,7 @@ int v9fs_client_create(FAR struct v9fs_client_s *client, uint32_t fid, struct iovec wiov[1]; struct iovec riov[1]; uint32_t flags = v9fs_map_open_flags(oflags); - uint32_t gid = getgid(); + uint32_t gid = getegid(); off_t offset = 0; int ret; @@ -1644,7 +1724,7 @@ static int v9fs_build_path_to_component(FAR const char *path, ****************************************************************************/ static int v9fs_client_walk_impl(FAR struct v9fs_client_s *client, - FAR const char *path, + uint32_t root, FAR const char *path, FAR const char **childname, FAR struct v9fs_rwalk_s *response, FAR char *response_payload, @@ -1727,7 +1807,7 @@ static int v9fs_client_walk_impl(FAR struct v9fs_client_s *client, total_len; request.header.type = V9FS_TWALK; request.header.tag = v9fs_get_tagid(client); - request.fid = client->root_fid; + request.fid = root; request.newfid = newfid; request.nwname = nwname; start = path; @@ -1814,7 +1894,7 @@ err: ****************************************************************************/ static int v9fs_client_walk_internal(FAR struct v9fs_client_s *client, - FAR const char *path, + uint32_t root, FAR const char *path, FAR const char **childname, bool nofollow, int symloop_count) @@ -1842,7 +1922,7 @@ static int v9fs_client_walk_internal(FAR struct v9fs_client_s *client, return -ENOMEM; } - ret = fid = v9fs_client_walk_impl(client, path, childname, + ret = fid = v9fs_client_walk_impl(client, root, path, childname, &response, response_payload, &nwname); #ifdef CONFIG_FS_LINKS @@ -1869,7 +1949,7 @@ static int v9fs_client_walk_internal(FAR struct v9fs_client_s *client, goto errout_with_symlink; } - fid = v9fs_client_walk_impl(client, symlink_path, NULL, + fid = v9fs_client_walk_impl(client, root, symlink_path, NULL, &response, response_payload, NULL); if (fid < 0) @@ -1933,9 +2013,9 @@ static int v9fs_client_walk_internal(FAR struct v9fs_client_s *client, goto errout_with_symlink; } - fid = v9fs_client_walk_impl(client, symlink_path, NULL, - &response, response_payload, - NULL); + fid = v9fs_client_walk_impl(client, root, symlink_path, + NULL, &response, + response_payload, NULL); if (fid < 0) { /* Walk failed, no point trying longer paths */ @@ -2049,7 +2129,7 @@ static int v9fs_client_walk_internal(FAR struct v9fs_client_s *client, snprintf(new_path, PATH_MAX, "%.*s%s%s", (int)(start - path), path, readlink_buf, end); - ret = v9fs_client_walk_internal(client, new_path, childname, + ret = v9fs_client_walk_internal(client, root, new_path, childname, nofollow, symloop_count + 1); goto errout_with_newpath; } @@ -2086,7 +2166,16 @@ errout_with_response: int v9fs_client_walk(FAR struct v9fs_client_s *client, FAR const char *path, FAR const char **childname, bool nofollow) { - return v9fs_client_walk_internal(client, path, childname, nofollow, 0); + int root; + + root = v9fs_client_root(client); + if (root < 0) + { + return root; + } + + return v9fs_client_walk_internal(client, root, path, childname, + nofollow, 0); } /**************************************************************************** @@ -2186,7 +2275,7 @@ int v9fs_client_init(FAR struct v9fs_client_s *client, /* Do Attach */ - ret = v9fs_client_attach(client, V9FS_NOFID, uname, aname); + ret = v9fs_client_attach(client, V9FS_NOFID, uname, aname, geteuid()); if (ret < 0) { goto out; @@ -2194,6 +2283,23 @@ int v9fs_client_init(FAR struct v9fs_client_s *client, client->root_fid = ret; client->tag_id = 1; + +#ifdef CONFIG_SCHED_USER_IDENTITY + /* Keep the names for the attach of other users */ + + client->root_uid = geteuid(); + client->uname = fs_heap_strdup(uname); + client->aname = fs_heap_strdup(aname); + if (client->uname == NULL || client->aname == NULL) + { + fs_heap_free(client->uname); + fs_heap_free(client->aname); + v9fs_client_clunk(client, client->root_fid); + ret = -ENOMEM; + goto out; + } +#endif + lib_put_pathbuffer(aname); return 0; @@ -2211,6 +2317,9 @@ out: int v9fs_client_uninit(FAR struct v9fs_client_s *client) { +#ifdef CONFIG_SCHED_USER_IDENTITY + FAR struct v9fs_root_s *root; +#endif int ret; ret = v9fs_client_clunk(client, client->root_fid); @@ -2219,6 +2328,18 @@ int v9fs_client_uninit(FAR struct v9fs_client_s *client) return ret; } +#ifdef CONFIG_SCHED_USER_IDENTITY + while ((root = client->roots) != NULL) + { + client->roots = root->next; + v9fs_client_clunk(client, root->fid); + fs_heap_free(root); + } + + fs_heap_free(client->uname); + fs_heap_free(client->aname); +#endif + v9fs_transport_destroy(client->transport); nxmutex_destroy(&client->lock); idr_destroy(client->fids); @@ -2327,7 +2448,7 @@ int v9fs_client_symlink(FAR struct v9fs_client_s *client, uint32_t fid, struct v9fs_rsymlink_s response; struct iovec wiov[1]; struct iovec riov[1]; - uint32_t gid = getgid(); + uint32_t gid = getegid(); off_t offset = 0; uint16_t symtgt_len; size_t name_len; diff --git a/fs/v9fs/client.h b/fs/v9fs/client.h index f018042e276..4652a0b6dc5 100644 --- a/fs/v9fs/client.h +++ b/fs/v9fs/client.h @@ -70,6 +70,15 @@ struct v9fs_transport_ops_s CODE void (*destroy)(FAR struct v9fs_transport_s *transport); }; +#ifdef CONFIG_SCHED_USER_IDENTITY +struct v9fs_root_s +{ + FAR struct v9fs_root_s *next; + uid_t uid; + uint32_t fid; +}; +#endif + struct v9fs_client_s { FAR struct v9fs_transport_s *transport; @@ -78,6 +87,12 @@ struct v9fs_client_s uint32_t root_fid; uint32_t tag_id; mutex_t lock; +#ifdef CONFIG_SCHED_USER_IDENTITY + uid_t root_uid; /* The user of root_fid */ + FAR struct v9fs_root_s *roots; /* The root fids of other users */ + FAR char *uname; + FAR char *aname; +#endif }; /****************************************************************************
