fuse: Fail all requests with invalid uids or gids (c9582eb0) · Commits · 戴 / test

Upon a cursory examinination the uid and gid of a fuse request are necessary for correct operation. Failing a fuse request where those values are not reliable seems a straight forward and reliable means of ensuring that fuse requests with bad data are not sent or processed. In most cases the vfs will avoid actions it suspects will cause an inode write back of an inode with an invalid uid or gid. But that does not map precisely to what fuse is doing, so test for this and solve this at the fuse level as well. Performing this work in fuse_req_init_context is cheap as the code is already performing the translation here and only needs to check the result of the translation to see if things are not representable in a form the fuse server can handle. [SzM] Don't zero the context for the nofail case, just keep using the munging version (makes sense for debugging and doesn't hurt). Signed-off-by:

Eric W. Biederman <ebiederm@xmission.com> Signed-off-by:

Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/dev.c

+13 −9

Original line number	Diff line number	Diff line
		@@ -112,13 +112,6 @@ static void __fuse_put_request(struct fuse_req *req)
		refcount_dec(&req->count);
		}

		static void fuse_req_init_context(struct fuse_conn fc, struct fuse_req req)
		{
		req->in.h.uid = from_kuid_munged(&init_user_ns, current_fsuid());
		req->in.h.gid = from_kgid_munged(&init_user_ns, current_fsgid());
		req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
		}

		void fuse_set_initialized(struct fuse_conn *fc)
		{
		/* Make sure stores before this are seen on another CPU */
		@@ -163,11 +156,19 @@ static struct fuse_req __fuse_get_req(struct fuse_conn fc, unsigned npages,
		goto out;
		}

		fuse_req_init_context(fc, req);
		req->in.h.uid = from_kuid(&init_user_ns, current_fsuid());
		req->in.h.gid = from_kgid(&init_user_ns, current_fsgid());
		req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);

		__set_bit(FR_WAITING, &req->flags);
		if (for_background)
		__set_bit(FR_BACKGROUND, &req->flags);

		if (unlikely(req->in.h.uid == ((uid_t)-1) \|\|
		req->in.h.gid == ((gid_t)-1))) {
		fuse_put_request(fc, req);
		return ERR_PTR(-EOVERFLOW);
		}
		return req;

		out:
		@@ -256,7 +257,10 @@ struct fuse_req fuse_get_req_nofail_nopages(struct fuse_conn fc,
		if (!req)
		req = get_reserved_req(fc, file);

		fuse_req_init_context(fc, req);
		req->in.h.uid = from_kuid_munged(&init_user_ns, current_fsuid());
		req->in.h.gid = from_kgid_munged(&init_user_ns, current_fsgid());
		req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);

		__set_bit(FR_WAITING, &req->flags);
		__clear_bit(FR_BACKGROUND, &req->flags);
		return req;

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