ANDROID: fuse-bpf: Use stored bpf for create_open

create_open would always take its parent directory's bpf for the created
object. Modify to use the bpf stored in fuse_dentry which is set by
lookup.

Bug: 291705489
Test: fuse_test passes, adb push file /sdcard/Android/data works
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Change-Id: I0a1ea2a291a8fdf67923f1827176b2ea96bd4c2d

fs/fuse/backing.c

@@ -208,6 +208,7 @@ int fuse_create_open_backing(
 		struct file *file, unsigned int flags, umode_t mode)
 {
 	struct fuse_inode *dir_fuse_inode = get_fuse_inode(dir);
+	struct fuse_dentry *fuse_entry = get_fuse_dentry(entry);
 	struct fuse_dentry *dir_fuse_dentry = get_fuse_dentry(entry->d_parent);
 	struct dentry *backing_dentry = NULL;
 	struct inode *inode = NULL;
@@ -239,19 +240,19 @@ int fuse_create_open_backing(
 	if (err)
 		goto out;
 
-	if (get_fuse_dentry(entry)->backing_path.dentry)
+	if (fuse_entry->backing_path.dentry)
-		path_put(&get_fuse_dentry(entry)->backing_path);
+		path_put(&fuse_entry->backing_path);
-	get_fuse_dentry(entry)->backing_path = (struct path) {
+	fuse_entry->backing_path = (struct path) {
 		.mnt = dir_fuse_dentry->backing_path.mnt,
 		.dentry = backing_dentry,
 	};
-	path_get(&get_fuse_dentry(entry)->backing_path);
+	path_get(&fuse_entry->backing_path);
 
 	if (d_inode)
 		target_nodeid = get_fuse_inode(d_inode)->nodeid;
 
 	inode = fuse_iget_backing(dir->i_sb, target_nodeid,
-			get_fuse_dentry(entry)->backing_path.dentry->d_inode);
+			fuse_entry->backing_path.dentry->d_inode);
 	if (!inode) {
 		err = -EIO;
 		goto out;
@@ -259,9 +260,8 @@ int fuse_create_open_backing(
 
 	if (get_fuse_inode(inode)->bpf)
 		bpf_prog_put(get_fuse_inode(inode)->bpf);
-	get_fuse_inode(inode)->bpf = dir_fuse_inode->bpf;
+	get_fuse_inode(inode)->bpf = fuse_entry->bpf;
-	if (get_fuse_inode(inode)->bpf)
+	fuse_entry->bpf = NULL;
-		bpf_prog_inc(dir_fuse_inode->bpf);
 
 	newent = d_splice_alias(inode, entry);
 	if (IS_ERR(newent)) {

tools/testing/selftests/filesystems/fuse/fuse_test.c

@@ -2009,6 +2009,44 @@ static int bpf_test_lookup_postfilter(const char *mount_dir)
 	return result;
 }
 
+/**
+ * Test that a file made via create_and_open correctly gets the bpf assigned
+ * from the negative lookup
+ * bpf blocks file open, but also removes itself from children
+ * This test will fail if the 'remove' is unsuccessful
+ */
+static int bpf_test_create_and_remove_bpf(const char *mount_dir)
+{
+	const char *file = "file";
+
+	int result = TEST_FAILURE;
+	int src_fd = -1;
+	int bpf_fd = -1;
+	int fuse_dev = -1;
+	int fd = -1;
+	int fd2 = -1;
+
+	TEST(src_fd = open(ft_src, O_DIRECTORY | O_RDONLY | O_CLOEXEC),
+	     src_fd != -1);
+	TESTEQUAL(install_elf_bpf("test_bpf.bpf", "test_create_remove", &bpf_fd,
+				  NULL, NULL), 0);
+	TESTEQUAL(mount_fuse_no_init(mount_dir, bpf_fd, src_fd, &fuse_dev), 0);
+	TEST(fd = s_creat(s_path(s(mount_dir), s(file)), 0777),
+	     fd != -1);
+	TEST(fd2 = s_open(s_path(s(mount_dir), s(file)), O_RDONLY),
+	     fd2 != -1);
+
+	result = TEST_SUCCESS;
+out:
+	close(fd2);
+	close(fd);
+	close(fuse_dev);
+	close(bpf_fd);
+	close(src_fd);
+	umount(mount_dir);
+	return result;
+}
+
 static void parse_range(const char *ranges, bool *run_test, size_t tests)
 {
 	size_t i;
@@ -2136,6 +2174,7 @@ int main(int argc, char *argv[])
 		MAKE_TEST(bpf_test_revalidate_handle_backing_fd),
 		MAKE_TEST(bpf_test_lookup_postfilter),
 		MAKE_TEST(flock_test),
+		MAKE_TEST(bpf_test_create_and_remove_bpf),
 	};
 #undef MAKE_TEST
 

tools/testing/selftests/filesystems/fuse/test_bpf.c

@@ -505,3 +505,29 @@ int lookuppostfilter_test(struct fuse_bpf_args *fa)
 		return FUSE_BPF_BACKING;
 	}
 }
+
+SEC("test_create_remove")
+int createremovebpf_test(struct fuse_bpf_args *fa)
+{
+	switch (fa->opcode) {
+	case FUSE_LOOKUP | FUSE_PREFILTER: {
+		return FUSE_BPF_BACKING | FUSE_BPF_POST_FILTER;
+	}
+
+	case FUSE_LOOKUP | FUSE_POSTFILTER: {
+		struct fuse_entry_bpf_out *febo = fa->out_args[1].value;
+
+		febo->bpf_action = FUSE_ACTION_REMOVE;
+		return 0;
+	}
+
+	case FUSE_OPEN | FUSE_PREFILTER: {
+		return -EIO;
+	}
+
+	default:
+		return FUSE_BPF_BACKING;
+	}
+}
+
+