• Gu Zheng's avatar
    mm/memory_hotplug.c: set zone->wait_table to null after freeing it · 85bd8399
    Gu Zheng authored
    Izumi found the following oops when hot re-adding a node:
    
        BUG: unable to handle kernel paging request at ffffc90008963690
        IP: __wake_up_bit+0x20/0x70
        Oops: 0000 [#1] SMP
        CPU: 68 PID: 1237 Comm: rs:main Q:Reg Not tainted 4.1.0-rc5 #80
        Hardware name: FUJITSU PRIMEQUEST2800E/SB, BIOS PRIMEQUEST 2000 Series BIOS Version 1.87 04/28/2015
        task: ffff880838df8000 ti: ffff880017b94000 task.ti: ffff880017b94000
        RIP: 0010:[<ffffffff810dff80>]  [<ffffffff810dff80>] __wake_up_bit+0x20/0x70
        RSP: 0018:ffff880017b97be8  EFLAGS: 00010246
        RAX: ffffc90008963690 RBX: 00000000003c0000 RCX: 000000000000a4c9
        RDX: 0000000000000000 RSI: ffffea101bffd500 RDI: ffffc90008963648
        RBP: ffff880017b97c08 R08: 0000000002000020 R09: 0000000000000000
        R10: 0000000000000000 R11: 0000000000000000 R12: ffff8a0797c73800
        R13: ffffea101bffd500 R14: 0000000000000001 R15: 00000000003c0000
        FS:  00007fcc7ffff700(0000) GS:ffff880874800000(0000) knlGS:0000000000000000
        CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
        CR2: ffffc90008963690 CR3: 0000000836761000 CR4: 00000000001407e0
        Call Trace:
          unlock_page+0x6d/0x70
          generic_write_end+0x53/0xb0
          xfs_vm_write_end+0x29/0x80 [xfs]
          generic_perform_write+0x10a/0x1e0
          xfs_file_buffered_aio_write+0x14d/0x3e0 [xfs]
          xfs_file_write_iter+0x79/0x120 [xfs]
          __vfs_write+0xd4/0x110
          vfs_write+0xac/0x1c0
          SyS_write+0x58/0xd0
          system_call_fastpath+0x12/0x76
        Code: 5d c3 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 48 83 ec 20 65 48 8b 04 25 28 00 00 00 48 89 45 f8 31 c0 48 8d 47 48 <48> 39 47 48 48 c7 45 e8 00 00 00 00 48 c7 45 f0 00 00 00 00 48
        RIP  [<ffffffff810dff80>] __wake_up_bit+0x20/0x70
         RSP <ffff880017b97be8>
        CR2: ffffc90008963690
    
    Reproduce method (re-add a node)::
      Hot-add nodeA --> remove nodeA --> hot-add nodeA (panic)
    
    This seems an use-after-free problem, and the root cause is
    zone->wait_table was not set to *NULL* after free it in
    try_offline_node.
    
    When hot re-add a node, we will reuse the pgdat of it, so does the zone
    struct, and when add pages to the target zone, it will init the zone
    first (including the wait_table) if the zone is not initialized.  The
    judgement of zone initialized is based on zone->wait_table:
    
    	static inline bool zone_is_initialized(struct zone *zone)
    	{
    		return !!zone->wait_table;
    	}
    
    so if we do not set the zone->wait_table to *NULL* after free it, the
    memory hotplug routine will skip the init of new zone when hot re-add
    the node, and the wait_table still points to the freed memory, then we
    will access the invalid address when trying to wake up the waiting
    people after the i/o operation with the page is done, such as mentioned
    above.
    Signed-off-by: default avatarGu Zheng <guz.fnst@cn.fujitsu.com>
    Reported-by: default avatarTaku Izumi <izumi.taku@jp.fujitsu.com>
    Reviewed by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Tang Chen <tangchen@cn.fujitsu.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    85bd8399
memory_hotplug.c 51.1 KB