Re: [PATCH v2] bootconfig: use memblock_free_late to free xbc memory to buddy

Qiang Zhang
2024-04-14T11:45:01Z

On Sat, Apr 13, 2024 at 09:21:38PM +0900, Masami Hiramatsu wrote:
>Hi Qiang,
>
>I found xbc_free_mem() missed to check !addr. When I booted kernel without
>bootconfig data but with "bootconfig" cmdline, I got a kernel crash below;
>
>
>[ 2.394904] ------------[ cut here ]------------
>[ 2.396490] kernel BUG at arch/x86/mm/physaddr.c:28!
>[ 2.398176] invalid opcode: 0000 [#1] PREEMPT SMP PTI
>[ 2.399388] CPU: 7 PID: 1 Comm: swapper/0 Tainted: G N 6.9.0-rc3-00004-g121fbb463836 #10
>[ 2.401579] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
>[ 2.403247] RIP: 0010:__phys_addr+0x40/0x60
>[ 2.404196] Code: 48 2b 05 fb a4 3d 01 48 05 00 00 00 80 48 39 c7 72 17 0f b6 0d ee 9e c0 01 48 89 c2 48 d3 ea 48 85 d2 75 05 c3 cc cc cc cc 90 <0f> 0b 48 03 05 e7 e2 9d 01 48 81 ff ff ff ff 1f 76 e8 90 0f6
>[ 2.407250] RSP: 0000:ffffc90000013f18 EFLAGS: 00010287
>[ 2.407991] RAX: 0000778000000000 RBX: ffffffff81c17940 RCX: 000000000080000a
>[ 2.408891] RDX: 000000000080000b RSI: ffff88800775f320 RDI: 0000000080000000
>[ 2.409727] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>[ 2.410555] R10: ffff888005028a60 R11: 000000000080000a R12: 0000000000000000
>[ 2.411423] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>[ 2.412155] FS: 0000000000000000(0000) GS:ffff88807d9c0000(0000) knlGS:0000000000000000
>[ 2.412970] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>[ 2.413550] CR2: 0000000000000000 CR3: 0000000002a48000 CR4: 00000000000006b0
>[ 2.414264] Call Trace:
>[ 2.414520] <TASK>
>[ 2.414755] ? die+0x37/0x90
>[ 2.415062] ? do_trap+0xe3/0x110
>[ 2.415451] ? __phys_addr+0x40/0x60
>[ 2.415822] ? do_error_trap+0x9c/0x120
>[ 2.416215] ? __phys_addr+0x40/0x60
>[ 2.416573] ? __phys_addr+0x40/0x60
>[ 2.416968] ? exc_invalid_op+0x53/0x70
>[ 2.417358] ? __phys_addr+0x40/0x60
>[ 2.417709] ? asm_exc_invalid_op+0x1a/0x20
>[ 2.418122] ? __pfx_kernel_init+0x10/0x10
>[ 2.418569] ? __phys_addr+0x40/0x60
>[ 2.418960] _xbc_exit+0x74/0xc0
>[ 2.419374] kernel_init+0x3a/0x1c0
>[ 2.419764] ret_from_fork+0x34/0x50
>[ 2.420132] ? __pfx_kernel_init+0x10/0x10
>[ 2.420578] ret_from_fork_asm+0x1a/0x30
>[ 2.420973] </TASK>
>[ 2.421200] Modules linked in:
>[ 2.421598] ---[ end trace 0000000000000000 ]---
>[ 2.422053] RIP: 0010:__phys_addr+0x40/0x60
>[ 2.422484] Code: 48 2b 05 fb a4 3d 01 48 05 00 00 00 80 48 39 c7 72 17 0f b6 0d ee 9e c0 01 48 89 c2 48 d3 ea 48 85 d2 75 05 c3 cc cc cc cc 90 <0f> 0b 48 03 05 e7 e2 9d 01 48 81 ff ff ff ff 1f 76 e8 90 0f6
>[ 2.424294] RSP: 0000:ffffc90000013f18 EFLAGS: 00010287
>[ 2.424769] RAX: 0000778000000000 RBX: ffffffff81c17940 RCX: 000000000080000a
>[ 2.425378] RDX: 000000000080000b RSI: ffff88800775f320 RDI: 0000000080000000
>[ 2.425993] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>[ 2.426589] R10: ffff888005028a60 R11: 000000000080000a R12: 0000000000000000
>[ 2.427156] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>[ 2.427746] FS: 0000000000000000(0000) GS:ffff88807d9c0000(0000) knlGS:0000000000000000
>[ 2.428368] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>[ 2.428820] CR2: 0000000000000000 CR3: 0000000002a48000 CR4: 00000000000006b0
>[ 2.429373] Kernel panic - not syncing: Fatal exception
>[ 2.429982] Kernel Offset: disabled
>[ 2.430261] ---[ end Kernel panic - not syncing: Fatal exception ]---
>
>Adding below patch fixed it.
>
>diff --git a/lib/bootconfig.c b/lib/bootconfig.c
>index f9a45adc6307..8841554432d5 100644
>--- a/lib/bootconfig.c
>+++ b/lib/bootconfig.c
>@@ -65,7 +65,7 @@ static inline void __init xbc_free_mem(void *addr, size_t size, bool early)
> {
> if (early)
> memblock_free(addr, size);
>- else
>+ else if (addr)
> memblock_free_late(__pa(addr), size);
> }
>
>Can you update with this fix?

Sure.

>
>Thank you,
>
>
>On Fri, 12 Apr 2024 22:18:20 +0900
>Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
>
>> On Fri, 12 Apr 2024 18:49:41 +0800
>> qiang4.zhang@linux.intel.com wrote:
>>
>> > 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>
>>
>> Looks good to me.
>>
>> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>>
>> Also,
>>
>> Fixes: 40caa127f3c7 ("init: bootconfig: Remove all bootconfig data when the init memory is removed")
>>
>> Let me pick this for bootconfig/fixes.
>>
>> Thanks!
>>
>> > ---
>> > 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
>> >
>>
>>
>> --
>> Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
>
>--
>Masami Hiramatsu (Google) <mhiramat@kernel.org>