From: Qiang Zhang qiang4.zhang@intel.com
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@vger.kernel.org Signed-off-by: Qiang Zhang qiang4.zhang@intel.com --- v3: - add NULL pointer check in memblock_free_late() path.
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..8841554432d5 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 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;