Allow changing the file mode, UID, and GID through SETATTR. This only really makes sense with allow-other, though (because without it, the effective access mode is fixed to be 0600 (u+rw) with qemu's user being the file's owner), so changing these stat fields is not allowed without allow-other.
Signed-off-by: Max Reitz <mre...@redhat.com> --- block/export/fuse.c | 48 ++++++++++++++++++++++++++++++++++----------- 1 file changed, 37 insertions(+), 11 deletions(-) diff --git a/block/export/fuse.c b/block/export/fuse.c index 1d54286d90..742e0af657 100644 --- a/block/export/fuse.c +++ b/block/export/fuse.c @@ -47,6 +47,10 @@ typedef struct FuseExport { bool writable; bool growable; bool allow_other; + + mode_t st_mode; + uid_t st_uid; + gid_t st_gid; } FuseExport; static GHashTable *exports; @@ -120,6 +124,13 @@ static int fuse_export_create(BlockExport *blk_exp, exp->growable = args->growable; exp->allow_other = args->allow_other; + exp->st_mode = S_IFREG | S_IRUSR; + if (exp->writable) { + exp->st_mode |= S_IWUSR; + } + exp->st_uid = getuid(); + exp->st_gid = getgid(); + ret = setup_fuse_export(exp, args->mountpoint, errp); if (ret < 0) { goto fail; @@ -329,7 +340,6 @@ static void fuse_getattr(fuse_req_t req, fuse_ino_t inode, int64_t length, allocated_blocks; time_t now = time(NULL); FuseExport *exp = fuse_req_userdata(req); - mode_t mode; length = blk_getlength(exp->common.blk); if (length < 0) { @@ -344,17 +354,12 @@ static void fuse_getattr(fuse_req_t req, fuse_ino_t inode, allocated_blocks = DIV_ROUND_UP(allocated_blocks, 512); } - mode = S_IFREG | S_IRUSR; - if (exp->writable) { - mode |= S_IWUSR; - } - statbuf = (struct stat) { .st_ino = inode, - .st_mode = mode, + .st_mode = exp->st_mode, .st_nlink = 1, - .st_uid = getuid(), - .st_gid = getgid(), + .st_uid = exp->st_uid, + .st_gid = exp->st_gid, .st_size = length, .st_blksize = blk_bs(exp->common.blk)->bl.request_alignment, .st_blocks = allocated_blocks, @@ -400,15 +405,23 @@ static int fuse_do_truncate(const FuseExport *exp, int64_t size, } /** - * Let clients set file attributes. Only resizing is supported. + * Let clients set file attributes. With allow_other, only resizing and + * changing permissions (st_mode, st_uid, st_gid) is allowed. Without + * allow_other, only resizing is supported. */ static void fuse_setattr(fuse_req_t req, fuse_ino_t inode, struct stat *statbuf, int to_set, struct fuse_file_info *fi) { FuseExport *exp = fuse_req_userdata(req); + int supported_attrs; int ret; - if (to_set & ~FUSE_SET_ATTR_SIZE) { + supported_attrs = FUSE_SET_ATTR_SIZE; + if (exp->allow_other) { + supported_attrs |= FUSE_SET_ATTR_MODE | FUSE_SET_ATTR_UID | + FUSE_SET_ATTR_GID; + } + if (to_set & ~supported_attrs) { fuse_reply_err(req, ENOTSUP); return; } @@ -426,6 +439,19 @@ static void fuse_setattr(fuse_req_t req, fuse_ino_t inode, struct stat *statbuf, } } + if (to_set & FUSE_SET_ATTR_MODE) { + /* Only allow changing the file mode, not the type */ + exp->st_mode = (statbuf->st_mode & 07777) | S_IFREG; + } + + if (to_set & FUSE_SET_ATTR_UID) { + exp->st_uid = statbuf->st_uid; + } + + if (to_set & FUSE_SET_ATTR_GID) { + exp->st_gid = statbuf->st_gid; + } + fuse_getattr(req, inode, fi); } -- 2.31.1