From: Qiang Zhang <qiang4.zhang@xxxxxxxxx>
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] ==================================================================
Cc: Stable@xxxxxxxxxxxxxxx
Signed-off-by: Qiang Zhang <qiang4.zhang@xxxxxxxxx>
---
v2:
- add an early flag in xbc_free_mem() to free memory back to memblock in
xbc_init error path or put memory to buddy allocator in normal xbc_exit.
---
include/linux/bootconfig.h | 7 ++++++-
lib/bootconfig.c | 19 +++++++++++--------
2 files changed, 17 insertions(+), 9 deletions(-)
diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
index e5ee2c694401..3f4b4ac527ca 100644
--- a/include/linux/bootconfig.h
+++ b/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
diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index c59d26068a64..f9a45adc6307 100644
--- a/lib/bootconfig.c
+++ b/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
+ 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;
--
2.39.2
