[PATCH] thunderbolt: Fix double free of drom buffer

[PATCH] thunderbolt: Fix double free of drom buffer

[Andreas Noever]

If tb_drom_read fails sw->drom is freed but not set to NULL. sw->drom
is then freed again in the error path of sw_switch_alloc.

The bug can be triggered by unplugging a thunderbolt device shortly
after it is detected by the thunderbolt driver.

Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org
---
 drivers/thunderbolt/eeprom.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
index 0dde34e..545c60c 100644
--- a/drivers/thunderbolt/eeprom.c
+++ b/drivers/thunderbolt/eeprom.c
@@ -444,6 +444,7 @@ int tb_drom_read(struct tb_switch *sw)
 	return tb_drom_parse_entries(sw);
 err:
 	kfree(sw->drom);
+	sw->drom = NULL;
 	return -EIO;
 
 }
-- 
2.8.0

Re: [PATCH] thunderbolt: Fix double free of drom buffer

[Bjorn Helgaas]

On Sun, Apr 10, 2016 at 12:48:27PM +0200, Andreas Noever wrote:
> If tb_drom_read fails sw->drom is freed but not set to NULL. sw->drom
> is then freed again in the error path of sw_switch_alloc.

s/sw_switch_alloc/tb_switch_alloc/ ?

> The bug can be triggered by unplugging a thunderbolt device shortly
> after it is detected by the thunderbolt driver.
> 
> Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
> Cc: Lukas Wunner <lukas@wunner.de>
> Cc: stable@vger.kernel.org

How far back would this need to be applied?  What is the commit where
the but was introduced?

I applied this to pci/thunderbolt for v4.7 with the following
changelog.  If I did it wrong, I'll gladly update it, especially if
you have specific symptoms of a bug or oops that would help people
find this fix.

    thunderbolt: Fix double free of drom buffer
    
    If tb_drom_read() fails, sw->drom is freed but not set to NULL.  sw->drom
    is then freed again in the error path of tb_switch_alloc().
    
    The bug can be triggered by unplugging a thunderbolt device shortly after
    it is detected by the thunderbolt driver.
    
    Clear sw->drom if tb_drom_read() fails.
    
    [bhelgaas: add Fixes:, stable versions of interest]
    Fixes: 343fcb8c70d7 ("thunderbolt: Fix nontrivial endpoint devices.")
    Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
    CC: stable@vger.kernel.org	# v3.17+
    CC: Lukas Wunner <lukas@wunner.de>

> ---
>  drivers/thunderbolt/eeprom.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
> index 0dde34e..545c60c 100644
> --- a/drivers/thunderbolt/eeprom.c
> +++ b/drivers/thunderbolt/eeprom.c
> @@ -444,6 +444,7 @@ int tb_drom_read(struct tb_switch *sw)
>  	return tb_drom_parse_entries(sw);
>  err:
>  	kfree(sw->drom);
> +	sw->drom = NULL;
>  	return -EIO;
>  
>  }
> -- 
> 2.8.0
> 
> --
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Re: [PATCH] thunderbolt: Fix double free of drom buffer

[Andreas Noever]

On Mon, May 2, 2016 at 7:30 PM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> On Sun, Apr 10, 2016 at 12:48:27PM +0200, Andreas Noever wrote:
>> If tb_drom_read fails sw->drom is freed but not set to NULL. sw->drom
>> is then freed again in the error path of sw_switch_alloc.
>
> s/sw_switch_alloc/tb_switch_alloc/ ?
>
>> The bug can be triggered by unplugging a thunderbolt device shortly
>> after it is detected by the thunderbolt driver.
>>
>> Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
>> Cc: Lukas Wunner <lukas@wunner.de>
>> Cc: stable@vger.kernel.org
>
> How far back would this need to be applied?  What is the commit where
> the but was introduced?
>
> I applied this to pci/thunderbolt for v4.7 with the following
> changelog.  If I did it wrong, I'll gladly update it, especially if
> you have specific symptoms of a bug or oops that would help people
> find this fix.
>
>     thunderbolt: Fix double free of drom buffer
>
>     If tb_drom_read() fails, sw->drom is freed but not set to NULL.  sw->drom
>     is then freed again in the error path of tb_switch_alloc().
>
>     The bug can be triggered by unplugging a thunderbolt device shortly after
>     it is detected by the thunderbolt driver.
>
>     Clear sw->drom if tb_drom_read() fails.
The changelog is correct. The bug can be triggered starting from
343fcb8c ("thunderbolt: Fix nontrivial endpoint devices.") which is in
3.17-rc1. I observed crashes during subsequent hotplug operations (pci
core, sometimes in pciehp). But by nature of a double free bug these
were not very reliable (used kasan to track it down).

Thanks
Andreas


>     [bhelgaas: add Fixes:, stable versions of interest]
>     Fixes: 343fcb8c70d7 ("thunderbolt: Fix nontrivial endpoint devices.")
>     Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
>     Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>     CC: stable@vger.kernel.org  # v3.17+
>     CC: Lukas Wunner <lukas@wunner.de>
>
>> ---
>>  drivers/thunderbolt/eeprom.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
>> index 0dde34e..545c60c 100644
>> --- a/drivers/thunderbolt/eeprom.c
>> +++ b/drivers/thunderbolt/eeprom.c
>> @@ -444,6 +444,7 @@ int tb_drom_read(struct tb_switch *sw)
>>       return tb_drom_parse_entries(sw);
>>  err:
>>       kfree(sw->drom);
>> +     sw->drom = NULL;
>>       return -EIO;
>>
>>  }
>> --
>> 2.8.0
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html