[PATCH Resend] Bluetooth: btmtk: avoid UAF in btmtk_process_coredump

[AngeloGioacchino Del Regno]

Il 10/12/24 20:36, Thadeu Lima de Souza Cascardo ha scritto:
> hci_devcd_append may lead to the release of the skb, so it cannot be
> accessed once it is called.
> 
> ==================================================================
> BUG: KASAN: slab-use-after-free in btmtk_process_coredump+0x2a7/0x2d0 [btmtk]
> Read of size 4 at addr ffff888033cfabb0 by task kworker/0:3/82
> 
> CPU: 0 PID: 82 Comm: kworker/0:3 Tainted: G     U             6.6.40-lockdep-03464-g1d8b4eb3060e #1 b0b3c1cc0c842735643fb411799d97921d1f688c
> Hardware name: Google Yaviks_Ufs/Yaviks_Ufs, BIOS Google_Yaviks_Ufs.15217.552.0 05/07/2024
> Workqueue: events btusb_rx_work [btusb]
> Call Trace:
>   <TASK>
>   dump_stack_lvl+0xfd/0x150
>   print_report+0x131/0x780
>   kasan_report+0x177/0x1c0
>   btmtk_process_coredump+0x2a7/0x2d0 [btmtk 03edd567dd71a65958807c95a65db31d433e1d01]
>   btusb_recv_acl_mtk+0x11c/0x1a0 [btusb 675430d1e87c4f24d0c1f80efe600757a0f32bec]
>   btusb_rx_work+0x9e/0xe0 [btusb 675430d1e87c4f24d0c1f80efe600757a0f32bec]
>   worker_thread+0xe44/0x2cc0
>   kthread+0x2ff/0x3a0
>   ret_from_fork+0x51/0x80
>   ret_from_fork_asm+0x1b/0x30
>   </TASK>
> 
> Allocated by task 82:
>   stack_trace_save+0xdc/0x190
>   kasan_set_track+0x4e/0x80
>   __kasan_slab_alloc+0x4e/0x60
>   kmem_cache_alloc+0x19f/0x360
>   skb_clone+0x132/0xf70
>   btusb_recv_acl_mtk+0x104/0x1a0 [btusb]
>   btusb_rx_work+0x9e/0xe0 [btusb]
>   worker_thread+0xe44/0x2cc0
>   kthread+0x2ff/0x3a0
>   ret_from_fork+0x51/0x80
>   ret_from_fork_asm+0x1b/0x30
> 
> Freed by task 1733:
>   stack_trace_save+0xdc/0x190
>   kasan_set_track+0x4e/0x80
>   kasan_save_free_info+0x28/0xb0
>   ____kasan_slab_free+0xfd/0x170
>   kmem_cache_free+0x183/0x3f0
>   hci_devcd_rx+0x91a/0x2060 [bluetooth]
>   worker_thread+0xe44/0x2cc0
>   kthread+0x2ff/0x3a0
>   ret_from_fork+0x51/0x80
>   ret_from_fork_asm+0x1b/0x30
> 
> The buggy address belongs to the object at ffff888033cfab40
>   which belongs to the cache skbuff_head_cache of size 232
> The buggy address is located 112 bytes inside of
>   freed 232-byte region [ffff888033cfab40, ffff888033cfac28)
> 
> The buggy address belongs to the physical page:
> page:00000000a174ba93 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x33cfa
> head:00000000a174ba93 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> anon flags: 0x4000000000000840(slab|head|zone=1)
> page_type: 0xffffffff()
> raw: 4000000000000840 ffff888100848a00 0000000000000000 0000000000000001
> raw: 0000000000000000 0000000080190019 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>   ffff888033cfaa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
>   ffff888033cfab00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>> ffff888033cfab80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                       ^
>   ffff888033cfac00: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
>   ffff888033cfac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> Check if we need to call hci_devcd_complete before calling
> hci_devcd_append. That requires that we check data->cd_info.cnt >=
> MTK_COREDUMP_NUM instead of data->cd_info.cnt > MTK_COREDUMP_NUM, as we
> increment data->cd_info.cnt only once the call to hci_devcd_append
> succeeds.
> 
> Fixes: 0b7015132878 ("Bluetooth: btusb: mediatek: add MediaTek devcoredump support")
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at igalia.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>