ANDROID: fuse-bpf: Fix the issue of abnormal lseek system calls

fuse_lseek_backing was returning the offset as an int, which would then
be treated as an ERR if in the range 4G-4096 and 4G.

Although the call would appear to work correctly, the file position
would be incorrect according to a subsequent fseek with SEEK_CUR.

Based on a change by chenyuwen <chenyuwen1@meizu.com> who found and
fixed this issue.

Bug: 319219307
Change-Id: I3aef5fb22751a72ce2bd7674ee081956a89fc752
Signed-off-by: chenyuwen <chenyuwen1@meizu.com>
Signed-off-by: Paul Lawrence <paullawrence@google.com>

fs/fuse/backing.c

@@ -401,23 +401,26 @@ int fuse_lseek_backing(struct fuse_bpf_args *fa, struct file *file, loff_t offse
 	struct file *backing_file = fuse_file->backing_file;
 	loff_t ret;
 
-	/* TODO: Handle changing of the file handle */
 	if (offset == 0) {
 		if (whence == SEEK_CUR) {
 			flo->offset = file->f_pos;
-			return flo->offset;
+			return 0;
 		}
 
 		if (whence == SEEK_SET) {
 			flo->offset = vfs_setpos(file, 0, 0);
-			return flo->offset;
+			return 0;
 		}
 	}
 
 	inode_lock(file->f_inode);
 	backing_file->f_pos = file->f_pos;
 	ret = vfs_llseek(backing_file, fli->offset, fli->whence);
-	flo->offset = ret;
+
+	if (!IS_ERR(ERR_PTR(ret))) {
+		flo->offset = ret;
+		ret = 0;
+	}
 	inode_unlock(file->f_inode);
 	return ret;
 }

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

@@ -255,7 +255,7 @@ static int bpf_test_partial(const char *mount_dir)
 	TEST(src_fd = open(ft_src, O_DIRECTORY | O_RDONLY | O_CLOEXEC),
 	     src_fd != -1);
 	TESTEQUAL(create_file(src_fd, s(test_name), 1, 2), 0);
-	TESTEQUAL(install_elf_bpf("test_bpf.bpf", "test_trace",
+	TESTEQUAL(install_elf_bpf("test_bpf.bpf", "test_partial",
 				  &bpf_fd, NULL, NULL), 0);
 	TESTEQUAL(mount_fuse(mount_dir, bpf_fd, src_fd, &fuse_dev), 0);
 
@@ -363,7 +363,7 @@ static int bpf_test_readdir(const char *mount_dir)
 	     src_fd != -1);
 	TESTEQUAL(create_file(src_fd, s(names[0]), 1, 2), 0);
 	TESTEQUAL(create_file(src_fd, s(names[1]), 1, 2), 0);
-	TESTEQUAL(install_elf_bpf("test_bpf.bpf", "test_trace",
+	TESTEQUAL(install_elf_bpf("test_bpf.bpf", "test_partial",
 				  &bpf_fd, NULL, NULL), 0);
 	TESTEQUAL(mount_fuse(mount_dir, bpf_fd, src_fd, &fuse_dev), 0);
 
@@ -1490,6 +1490,8 @@ static int bpf_test_statfs(const char *mount_dir)
 static int bpf_test_lseek(const char *mount_dir)
 {
 	const char *file = "real";
+	const char *sparse_file = "sparse";
+	const off_t sparse_length = 0x100000000u;
 	const char *test_data = "data";
 	int result = TEST_FAILURE;
 	int src_fd = -1;
@@ -1504,6 +1506,12 @@ static int bpf_test_lseek(const char *mount_dir)
 	TESTEQUAL(write(fd, test_data, strlen(test_data)), strlen(test_data));
 	TESTSYSCALL(close(fd));
 	fd = -1;
+	TEST(fd = openat(src_fd, sparse_file, O_CREAT | O_RDWR | O_CLOEXEC,
+			 0777),
+	     fd != -1);
+	TESTSYSCALL(ftruncate(fd, sparse_length));
+	TESTSYSCALL(close(fd));
+	fd = -1;
 	TESTEQUAL(install_elf_bpf("test_bpf.bpf", "test_trace",
 				  &bpf_fd, NULL, NULL), 0);
 	TESTEQUAL(mount_fuse(mount_dir, bpf_fd, src_fd, &fuse_dev), 0);
@@ -1518,6 +1526,18 @@ static int bpf_test_lseek(const char *mount_dir)
 	TESTEQUAL(bpf_test_trace("lseek"), 0);
 	TESTEQUAL(lseek(fd, 1, SEEK_DATA), 1);
 	TESTEQUAL(bpf_test_trace("lseek"), 0);
+	TESTSYSCALL(close(fd));
+	fd = -1;
+
+	TEST(fd = s_open(s_path(s(mount_dir), s(sparse_file)),
+			 O_RDONLY | O_CLOEXEC),
+	     fd != -1);
+	TESTEQUAL(lseek(fd, -256, SEEK_END), sparse_length - 256);
+	TESTEQUAL(lseek(fd, 0, SEEK_CUR), sparse_length - 256);
+
+	TESTSYSCALL(close(fd));
+	fd = -1;
+
 	result = TEST_SUCCESS;
 out:
 	close(fd);

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

@@ -28,9 +28,9 @@ int readdir_test(struct fuse_bpf_args *fa)
 	}
 }
 
-SEC("test_trace")
+SEC("test_partial")
 /* return FUSE_BPF_BACKING to use backing fs, 0 to pass to usermode */
-int trace_test(struct fuse_bpf_args *fa)
+int partial_test(struct fuse_bpf_args *fa)
 {
 	switch (fa->opcode) {
 	case FUSE_LOOKUP | FUSE_PREFILTER: {
@@ -329,6 +329,195 @@ int trace_test(struct fuse_bpf_args *fa)
 	}
 }
 
+SEC("test_trace")
+/* return FUSE_BPF_BACKING to use backing fs, 0 to pass to usermode */
+int trace_test(struct fuse_bpf_args *fa)
+{
+	switch (fa->opcode) {
+	case FUSE_LOOKUP | FUSE_PREFILTER: {
+		/* real and partial use backing file */
+		const char *name = fa->in_args[0].value;
+
+		bpf_printk("lookup %s", name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_ACCESS | FUSE_PREFILTER: {
+		bpf_printk("Access: %d", fa->nodeid);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_CREATE | FUSE_PREFILTER:
+		bpf_printk("Create: %d", fa->nodeid);
+		return FUSE_BPF_BACKING;
+
+	case FUSE_MKNOD | FUSE_PREFILTER: {
+		const struct fuse_mknod_in *fmi = fa->in_args[0].value;
+		const char *name = fa->in_args[1].value;
+
+		bpf_printk("mknod %s %x %x", name, fmi->rdev | fmi->mode, fmi->umask);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_MKDIR | FUSE_PREFILTER: {
+		const struct fuse_mkdir_in *fmi = fa->in_args[0].value;
+		const char *name = fa->in_args[1].value;
+
+		bpf_printk("mkdir %s %x %x", name, fmi->mode, fmi->umask);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_RMDIR | FUSE_PREFILTER: {
+		const char *name = fa->in_args[0].value;
+
+		bpf_printk("rmdir %s", name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_RENAME | FUSE_PREFILTER: {
+		const char *oldname = fa->in_args[1].value;
+		const char *newname = fa->in_args[2].value;
+
+		bpf_printk("rename from %s", oldname);
+		bpf_printk("rename to %s", newname);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_RENAME2 | FUSE_PREFILTER: {
+		const struct fuse_rename2_in *fri = fa->in_args[0].value;
+		uint32_t flags = fri->flags;
+		const char *oldname = fa->in_args[1].value;
+		const char *newname = fa->in_args[2].value;
+
+		bpf_printk("rename(%x) from %s", flags, oldname);
+		bpf_printk("rename to %s", newname);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_UNLINK | FUSE_PREFILTER: {
+		const char *name = fa->in_args[0].value;
+
+		bpf_printk("unlink %s", name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_LINK | FUSE_PREFILTER: {
+		const struct fuse_link_in *fli = fa->in_args[0].value;
+		const char *link_name = fa->in_args[1].value;
+
+		bpf_printk("link %d %s", fli->oldnodeid, link_name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_SYMLINK | FUSE_PREFILTER: {
+		const char *link_name = fa->in_args[0].value;
+		const char *link_dest = fa->in_args[1].value;
+
+		bpf_printk("symlink from %s", link_name);
+		bpf_printk("symlink to %s", link_dest);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_READLINK | FUSE_PREFILTER: {
+		const char *link_name = fa->in_args[0].value;
+
+		bpf_printk("readlink from", link_name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_OPEN | FUSE_PREFILTER: {
+		bpf_printk("open");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_OPEN | FUSE_POSTFILTER:
+		bpf_printk("open postfilter");
+		return FUSE_BPF_USER_FILTER;
+
+	case FUSE_READ | FUSE_PREFILTER: {
+		const struct fuse_read_in *fri = fa->in_args[0].value;
+
+		bpf_printk("read %llu", fri->offset);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_GETATTR | FUSE_PREFILTER: {
+		bpf_printk("getattr");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_SETATTR | FUSE_PREFILTER: {
+		bpf_printk("setattr");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_OPENDIR | FUSE_PREFILTER: {
+		bpf_printk("opendir");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_READDIR | FUSE_PREFILTER: {
+		bpf_printk("readdir");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_FLUSH | FUSE_PREFILTER: {
+		bpf_printk("Flush");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_GETXATTR | FUSE_PREFILTER: {
+		const char *name = fa->in_args[1].value;
+
+		bpf_printk("getxattr %s", name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_LISTXATTR | FUSE_PREFILTER: {
+		const char *name = fa->in_args[1].value;
+
+		bpf_printk("listxattr %s", name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_SETXATTR | FUSE_PREFILTER: {
+		const char *name = fa->in_args[1].value;
+		unsigned int size = fa->in_args[2].size;
+
+		bpf_printk("setxattr %s %u", name, size);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_REMOVEXATTR | FUSE_PREFILTER: {
+		const char *name = fa->in_args[0].value;
+
+		bpf_printk("removexattr %s", name);
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_CANONICAL_PATH | FUSE_PREFILTER: {
+		bpf_printk("canonical_path");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_STATFS | FUSE_PREFILTER: {
+		bpf_printk("statfs");
+		return FUSE_BPF_BACKING;
+	}
+
+	case FUSE_LSEEK | FUSE_PREFILTER: {
+		const struct fuse_lseek_in *fli = fa->in_args[0].value;
+
+		bpf_printk("lseek type:%d, offset:%lld", fli->whence, fli->offset);
+		return FUSE_BPF_BACKING;
+	}
+
+	default:
+		bpf_printk("Unknown opcode %d", fa->opcode);
+		return FUSE_BPF_BACKING;
+	}
+}
+
 SEC("test_hidden")
 int trace_hidden(struct fuse_bpf_args *fa)
 {