linux-kernel - [PATCH] bootconfig: use memblock_free

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Message-Id: <20240412020325.290330-1-qiang4.zhang@linux.intel.com>
Date: Fri, 12 Apr 2024 10:03:26 +0800
From: qiang4.zhang@...ux.intel.com
To: Masami Hiramatsu <mhiramat@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	Qiang Zhang <qiang4.zhang@...el.com>
Subject: [PATCH] bootconfig: use memblock_free_late to free xbc memory to buddy

From: Qiang Zhang <qiang4.zhang@...el.com>

On the time to free xbc memory, memblock 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.

[    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] ==================================================================

Signed-off-by: Qiang Zhang <qiang4.zhang@...el.com>
---
 lib/bootconfig.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index c59d26068a64..4524ee944df0 100644
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -63,7 +63,7 @@ static inline void * __init xbc_alloc_mem(size_t size)
 
 static inline void __init xbc_free_mem(void *addr, size_t size)
 {
-	memblock_free(addr, size);
+	memblock_free_late(__pa(addr), size);
 }
 
 #else /* !__KERNEL__ */
-- 
2.39.2