bootconfig: use memblock_free_late to free xbc memory to buddy

On the time to free xbc memory in xbc_exit(), memblock may has handed
over memory to buddy allocator. So it doesn't make sense to free memory
back to memblock. memblock_free() called by xbc_exit() even causes UAF bugs
on architectures with CONFIG_ARCH_KEEP_MEMBLOCK disabled like x86.
Following KASAN logs shows this case.

This patch fixes the xbc memory free problem by calling memblock_free()
in early xbc init error rewind path and calling memblock_free_late() in
xbc exit path to free memory to buddy allocator.

[    9.410890] ==================================================================
[    9.418962] BUG: KASAN: use-after-free in memblock_isolate_range+0x12d/0x260
[    9.426850] Read of size 8 at addr ffff88845dd30000 by task swapper/0/1

[    9.435901] CPU: 9 PID: 1 Comm: swapper/0 Tainted: G     U             6.9.0-rc3-00208-g586b5dfb51b9 #5
[    9.446403] Hardware name: Intel Corporation RPLP LP5 (CPU:RaptorLake)/RPLP LP5 (ID:13), BIOS IRPPN02.01.01.00.00.19.015.D-00000000 Dec 28 2023
[    9.460789] Call Trace:
[    9.463518]  <TASK>
[    9.465859]  dump_stack_lvl+0x53/0x70
[    9.469949]  print_report+0xce/0x610
[    9.473944]  ? __virt_addr_valid+0xf5/0x1b0
[    9.478619]  ? memblock_isolate_range+0x12d/0x260
[    9.483877]  kasan_report+0xc6/0x100
[    9.487870]  ? memblock_isolate_range+0x12d/0x260
[    9.493125]  memblock_isolate_range+0x12d/0x260
[    9.498187]  memblock_phys_free+0xb4/0x160
[    9.502762]  ? __pfx_memblock_phys_free+0x10/0x10
[    9.508021]  ? mutex_unlock+0x7e/0xd0
[    9.512111]  ? __pfx_mutex_unlock+0x10/0x10
[    9.516786]  ? kernel_init_freeable+0x2d4/0x430
[    9.521850]  ? __pfx_kernel_init+0x10/0x10
[    9.526426]  xbc_exit+0x17/0x70
[    9.529935]  kernel_init+0x38/0x1e0
[    9.533829]  ? _raw_spin_unlock_irq+0xd/0x30
[    9.538601]  ret_from_fork+0x2c/0x50
[    9.542596]  ? __pfx_kernel_init+0x10/0x10
[    9.547170]  ret_from_fork_asm+0x1a/0x30
[    9.551552]  </TASK>

[    9.555649] The buggy address belongs to the physical page:
[    9.561875] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x45dd30
[    9.570821] flags: 0x200000000000000(node=0|zone=2)
[    9.576271] page_type: 0xffffffff()
[    9.580167] raw: 0200000000000000 ffffea0011774c48 ffffea0012ba1848 0000000000000000
[    9.588823] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
[    9.597476] page dumped because: kasan: bad access detected

[    9.605362] Memory state around the buggy address:
[    9.610714]  ffff88845dd2ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[    9.618786]  ffff88845dd2ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[    9.626857] >ffff88845dd30000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[    9.634930]                    ^
[    9.638534]  ffff88845dd30080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[    9.646605]  ffff88845dd30100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[    9.654675] ==================================================================

Link: https://lore.kernel.org/all/[email protected]/

Fixes: 40caa12 ("init: bootconfig: Remove all bootconfig data when the init memory is removed")
Cc: [email protected]
Signed-off-by: Qiang Zhang <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

Author: zhangqiang4

include/linux/bootconfig.h

@@ -288,7 +288,12 @@ int __init xbc_init(const char *buf, size_t size, const char **emsg, int *epos);
 int __init xbc_get_info(int *node_size, size_t *data_size);
 
 /* XBC cleanup data structures */
-void __init xbc_exit(void);
+void __init _xbc_exit(bool early);
+
+static inline void xbc_exit(void)
+{
+	_xbc_exit(false);
+}
 
 /* XBC embedded bootconfig data in kernel */
 #ifdef CONFIG_BOOT_CONFIG_EMBED

lib/bootconfig.c

@@ -61,9 +61,12 @@ static inline void * __init xbc_alloc_mem(size_t size)
 	return memblock_alloc(size, SMP_CACHE_BYTES);
 }
 
-static inline void __init xbc_free_mem(void *addr, size_t size)
+static inline void __init xbc_free_mem(void *addr, size_t size, bool early)
 {
-	memblock_free(addr, size);
+	if (early)
+		memblock_free(addr, size);
+	else if (addr)
+		memblock_free_late(__pa(addr), size);
 }
 
 #else /* !__KERNEL__ */
@@ -73,7 +76,7 @@ static inline void *xbc_alloc_mem(size_t size)
 	return malloc(size);
 }
 
-static inline void xbc_free_mem(void *addr, size_t size)
+static inline void xbc_free_mem(void *addr, size_t size, bool early)
 {
 	free(addr);
 }
@@ -904,13 +907,13 @@ static int __init xbc_parse_tree(void)
  * If you need to reuse xbc_init() with new boot config, you can
  * use this.
  */
-void __init xbc_exit(void)
+void __init _xbc_exit(bool early)
 {
-	xbc_free_mem(xbc_data, xbc_data_size);
+	xbc_free_mem(xbc_data, xbc_data_size, early);
 	xbc_data = NULL;
 	xbc_data_size = 0;
 	xbc_node_num = 0;
-	xbc_free_mem(xbc_nodes, sizeof(struct xbc_node) * XBC_NODE_MAX);
+	xbc_free_mem(xbc_nodes, sizeof(struct xbc_node) * XBC_NODE_MAX, early);
 	xbc_nodes = NULL;
 	brace_index = 0;
 }
@@ -963,7 +966,7 @@ int __init xbc_init(const char *data, size_t size, const char **emsg, int *epos)
 	if (!xbc_nodes) {
 		if (emsg)
 			*emsg = "Failed to allocate bootconfig nodes";
-		xbc_exit();
+		_xbc_exit(true);
 		return -ENOMEM;
 	}
 	memset(xbc_nodes, 0, sizeof(struct xbc_node) * XBC_NODE_MAX);
@@ -977,7 +980,7 @@ int __init xbc_init(const char *data, size_t size, const char **emsg, int *epos)
 			*epos = xbc_err_pos;
 		if (emsg)
 			*emsg = xbc_err_msg;
-		xbc_exit();
+		_xbc_exit(true);
 	} else
 		ret = xbc_node_num;