Re: [Bug 1886362] [NEW] Heap use-after-free in lduw_he_p through e1000e_write_to_rx_buffers

[Jason Wang <1886362@bugs.launchpad.net>]

On 2020/7/10 下午6:37, Li Qiang wrote:
> Paolo Bonzini <pbonzini@redhat.com> 于2020年7月10日周五 上午1:36写道：
>> On 09/07/20 17:51, Li Qiang wrote:
>>> Maybe we should check whether the address is a RAM address in 'dma_memory_rw'?
>>> But it is a hot path. I'm not sure it is right. Hope more discussion.
>> Half of the purpose of dma-helpers.c (as opposed to address_space_*
>> functions in exec.c) is exactly to support writes to MMIO.  This is
> Hi Paolo,
>
> Could you please explain more about this(to support writes to MMIO).
> I can just see the dma helpers with sg DMA, not related with MMIO.


Please refer doc/devel/memory.rst.

The motivation of memory API is to allow support modeling different 
memory regions. DMA to MMIO is allowed in hardware so Qemu should 
emulate this behaviour.


>
>
>> especially true of dma_blk_io, which takes care of doing the DMA via a
>> bounce buffer, possibly in multiple steps and even blocking due to
>> cpu_register_map_client.
>>
>> For dma_memory_rw this is not needed, so it only needs to handle
>> QEMUSGList, but I think the design should be the same.
>>
>> However, this is indeed a nightmare for re-entrancy.  The easiest
>> solution is to delay processing of descriptors to a bottom half whenever
>> MMIO is doing something complicated.  This is also better for latency
>> because it will free the vCPU thread more quickly and leave the work to
>> the I/O thread.
> Do you mean we define a per-e1000e bottom half. And in the MMIO write
> or packet send
> trigger this bh?


Probably a TX bh.


> So even if we again trigger the MMIO write, then
> second bh will not be executed?


Bh is serialized so no re-entrancy issue.

Thanks


>
>
> Thanks,
> Li Qiang
>
>> Paolo
>>

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https://bugs.launchpad.net/bugs/1886362

Title:
  Heap use-after-free in lduw_he_p through e1000e_write_to_rx_buffers

Status in QEMU:
  New

Bug description:
  Hello,
  This reproducer causes a heap-use-after free. QEMU Built with --enable-sanitizers:
  cat << EOF | ./i386-softmmu/qemu-system-i386 -M q35,accel=qtest \
  -qtest stdio -nographic -monitor none -serial none
  outl 0xcf8 0x80001010
  outl 0xcfc 0xe1020000
  outl 0xcf8 0x80001014
  outl 0xcf8 0x80001004
  outw 0xcfc 0x7
  outl 0xcf8 0x800010a2
  write 0xe102003b 0x1 0xff
  write 0xe1020103 0x1e 0xffffff055c5e5c30be4511d084ffffffffffffffffffffffffffffffffff
  write 0xe1020420 0x4 0xffffffff
  write 0xe1020424 0x4 0xffffffff
  write 0xe102042b 0x1 0xff
  write 0xe1020430 0x4 0x055c5e5c
  write 0x5c041 0x1 0x04
  write 0x5c042 0x1 0x02
  write 0x5c043 0x1 0xe1
  write 0x5c048 0x1 0x8a
  write 0x5c04a 0x1 0x31
  write 0x5c04b 0x1 0xff
  write 0xe1020403 0x1 0xff
  EOF

  The Output:
  ==22689==ERROR: AddressSanitizer: heap-use-after-free on address 0x62500026800e at pc 0x55b93bb18bfa bp 0x7fffdbe844f0 sp 0x7fffdbe83cb8
  READ of size 2 at 0x62500026800e thread T0
      #0  in __asan_memcpy (/build/i386-softmmu/qemu-system-i386+)
      #1  in lduw_he_p /include/qemu/bswap.h:332:5
      #2  in ldn_he_p /include/qemu/bswap.h:550:1
      #3  in flatview_write_continue /exec.c:3145:19
      #4  in flatview_write /exec.c:3186:14
      #5  in address_space_write /exec.c:3280:18
      #6  in address_space_rw /exec.c:3290:16
      #7  in dma_memory_rw_relaxed /include/sysemu/dma.h:87:18
      #8  in dma_memory_rw /include/sysemu/dma.h:113:12
      #9  in pci_dma_rw /include/hw/pci/pci.h:789:5
      #10  in pci_dma_write /include/hw/pci/pci.h:802:12
      #11  in e1000e_write_to_rx_buffers /hw/net/e1000e_core.c:1412:9
      #12  in e1000e_write_packet_to_guest /hw/net/e1000e_core.c:1582:21
      #13  in e1000e_receive_iov /hw/net/e1000e_core.c:1709:9
      #14  in e1000e_nc_receive_iov /hw/net/e1000e.c:213:12
      #15  in net_tx_pkt_sendv /hw/net/net_tx_pkt.c:544:9
      #16  in net_tx_pkt_send /hw/net/net_tx_pkt.c:620:9
      #17  in net_tx_pkt_send_loopback /hw/net/net_tx_pkt.c:633:11
      #18  in e1000e_tx_pkt_send /hw/net/e1000e_core.c:664:16
      #19  in e1000e_process_tx_desc /hw/net/e1000e_core.c:743:17
      #20  in e1000e_start_xmit /hw/net/e1000e_core.c:934:9
      #21  in e1000e_set_tctl /hw/net/e1000e_core.c:2431:9
      #22  in e1000e_core_write /hw/net/e1000e_core.c:3265:9
      #23  in e1000e_mmio_write /hw/net/e1000e.c:109:5
      #24  in memory_region_write_accessor /memory.c:483:5
      #25  in access_with_adjusted_size /memory.c:544:18
      #26  in memory_region_dispatch_write /memory.c:1476:16
      #27  in flatview_write_continue /exec.c:3146:23
      #28  in flatview_write /exec.c:3186:14
      #29  in address_space_write /exec.c:3280:18
      #30  in qtest_process_command /qtest.c:567:9
      #31  in qtest_process_inbuf /qtest.c:710:9
      #32  in qtest_read /qtest.c:722:5
      #33  in qemu_chr_be_write_impl /chardev/char.c:188:9
      #34  in qemu_chr_be_write /chardev/char.c:200:9
      #35  in fd_chr_read /chardev/char-fd.c:68:9
      #36  in qio_channel_fd_source_dispatch /io/channel-watch.c:84:12
      #37  in g_main_context_dispatch (/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0+)
      #38  in glib_pollfds_poll /util/main-loop.c:219:9
      #39  in os_host_main_loop_wait /util/main-loop.c:242:5
      #40  in main_loop_wait /util/main-loop.c:518:11
      #41  in qemu_main_loop /softmmu/vl.c:1664:9
      #42  in main /softmmu/main.c:52:5
      #43  in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+)
      #44  in _start (/build/i386-softmmu/qemu-system-i386+)

  0x62500026800e is located 14 bytes inside of 138-byte region [0x625000268000,0x62500026808a)
  freed by thread T0 here:
      #0  in free (/build/i386-softmmu/qemu-system-i386+)
      #1  in qemu_vfree /util/oslib-posix.c:238:5
      #2  in address_space_unmap /exec.c:3616:5
      #3  in dma_memory_unmap /include/sysemu/dma.h:148:5
      #4  in pci_dma_unmap /include/hw/pci/pci.h:839:5
      #5  in net_tx_pkt_reset /hw/net/net_tx_pkt.c:453:9
      #6  in e1000e_process_tx_desc /hw/net/e1000e_core.c:749:9
      #7  in e1000e_start_xmit /hw/net/e1000e_core.c:934:9
      #8  in e1000e_set_tctl /hw/net/e1000e_core.c:2431:9
      #9  in e1000e_core_write /hw/net/e1000e_core.c:3265:9
      #10  in e1000e_mmio_write /hw/net/e1000e.c:109:5
      #11  in memory_region_write_accessor /memory.c:483:5
      #12  in access_with_adjusted_size /memory.c:544:18
      #13  in memory_region_dispatch_write /memory.c:1476:16
      #14  in flatview_write_continue /exec.c:3146:23
      #15  in flatview_write /exec.c:3186:14
      #16  in address_space_write /exec.c:3280:18
      #17  in address_space_rw /exec.c:3290:16
      #18  in dma_memory_rw_relaxed /include/sysemu/dma.h:87:18
      #19  in dma_memory_rw /include/sysemu/dma.h:113:12
      #20  in pci_dma_rw /include/hw/pci/pci.h:789:5
      #21  in pci_dma_write /include/hw/pci/pci.h:802:12
      #22  in e1000e_write_to_rx_buffers /hw/net/e1000e_core.c:1412:9
      #23  in e1000e_write_packet_to_guest /hw/net/e1000e_core.c:1582:21
      #24  in e1000e_receive_iov /hw/net/e1000e_core.c:1709:9
      #25  in e1000e_nc_receive_iov /hw/net/e1000e.c:213:12
      #26  in net_tx_pkt_sendv /hw/net/net_tx_pkt.c:544:9
      #27  in net_tx_pkt_send /hw/net/net_tx_pkt.c:620:9
      #28  in net_tx_pkt_send_loopback /hw/net/net_tx_pkt.c:633:11
      #29  in e1000e_tx_pkt_send /hw/net/e1000e_core.c:664:16

  previously allocated by thread T0 here:
      #0  in posix_memalign (/build/i386-softmmu/qemu-system-i386+)
      #1  in qemu_try_memalign /util/oslib-posix.c:198:11
      #2  in qemu_memalign /util/oslib-posix.c:214:27
      #3  in address_space_map /exec.c:3558:25
      #4  in dma_memory_map /include/sysemu/dma.h:138:9
      #5  in pci_dma_map /include/hw/pci/pci.h:832:11
      #6  in net_tx_pkt_add_raw_fragment /hw/net/net_tx_pkt.c:391:24
      #7  in e1000e_process_tx_desc /hw/net/e1000e_core.c:731:14
      #8  in e1000e_start_xmit /hw/net/e1000e_core.c:934:9
      #9  in e1000e_set_tctl /hw/net/e1000e_core.c:2431:9
      #10  in e1000e_core_write /hw/net/e1000e_core.c:3265:9
      #11  in e1000e_mmio_write /hw/net/e1000e.c:109:5
      #12  in memory_region_write_accessor /memory.c:483:5
      #13  in access_with_adjusted_size /memory.c:544:18
      #14  in memory_region_dispatch_write /memory.c:1476:16
      #15  in flatview_write_continue /exec.c:3146:23
      #16  in flatview_write /exec.c:3186:14
      #17  in address_space_write /exec.c:3280:18
      #18  in qtest_process_command /qtest.c:567:9
      #19  in qtest_process_inbuf /qtest.c:710:9
      #20  in qtest_read /qtest.c:722:5
      #21  in qemu_chr_be_write_impl /chardev/char.c:188:9
      #22  in qemu_chr_be_write /chardev/char.c:200:9
      #23  in fd_chr_read /chardev/char-fd.c:68:9
      #24  in qio_channel_fd_source_dispatch /io/channel-watch.c:84:12
      #25  in g_main_context_dispatch (/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0+)

  -Alex

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