[BUG] double free in dfu_free_entities()

[Heinrich Schuchardt]

On 3/11/21 9:18 AM, Lukasz Majewski wrote:
> Hi Heinrich,
>
>> Hello Lukasz,
>>
>> Jose and I have observed segmentation violations when
>> dfu_free_entities() is called.
>>
>
> Thanks for finding them.
>
>> In our scenario we have:
>>
>> dfu_alt_info=
>> sf 0:0=u-boot-bin raw 0x100000 0x50000;u-boot-env raw 0x150000
>> 0x200000
>>
>> dfu_free_entities() is called with these entries in dfu:
>>
>> u-boot-env:
>>    dfu->data.sf.dev 0000000015baf420 m25p16
>>    dfu->data.sf.dev->dev 0000000015888410 spi.bin at 0
>> u-boot-bin:
>>    dfu->data.sf.dev 0000000015baf420 m25p16
>>    dfu->data.sf.dev->dev 0000000015888410 spi.bin at 0
>>
>> The same device is released twice which eventually leads to the
>> segmentation fault in device_chld_remove().
>
> If I remember correctly that was fixed some time ago... Maybe something
> has changed with recent patches.
>
> Was it working before? Or is the above scenario a new one?

Jose and Takahiro have provided patches that exercise DFU by repeatedly
calling dfu_init_env_entities() and dfu_free_entities(). See function
efi_get_dfu_info().

Furthermore for testing we use a dfu_alt_info with multiple images on
the same device.

No change was done in this part of DFU since 2014. So this is a
longstanding problem that we now uncovered.

[PATCH 1/1] mtd: spi_flash_free()
https://lists.denx.de/pipermail/u-boot/2021-March/443915.html

fixes the issue for the case of DM_SPI_FLASH.

But we should also address the DFU system itself.

Best regards

Heinrich

>
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> device_chld_remove (
>> dev=dev at entry=0x5555557f6750 <av_+1936>, drv=drv at entry=0x0,
>> flags=flags at entry=1)
>> at drivers/core/device-remove.c:55
>> 55 list_for_each_entry_safe(pos, n, &dev->child_head, sibling_node) {
>>
>> We must ensure that dfu_free_entities() removes each device only once.
>>
>> Another bug in dfu_free_entities() is that only the first list member
>> is freed. free() should be called for all list members.
>
> Yes. Correct.
>
>>
>> Best regards
>>
>> Heinrich
>>
>>
>>
>
>
>
>
> Best regards,
>
> Lukasz Majewski
>
> --
>
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>