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

Masami Hiramatsu
2024-04-13T12:21:43Z

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?

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>