In the Linux kernel, the following vulnerability has been resolved:
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]