From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Nathan Nye <nnye@whitebeamsec.com>
Cc: libc-help@sourceware.org
Subject: Re: Possible glibc 2.35 ARM regression in LD_BIND_NOT
Date: Tue, 5 Jul 2022 14:04:12 -0300 [thread overview]
Message-ID: <0B99F4E6-2C9D-4346-B60F-D351A75936D4@linaro.org> (raw)
In-Reply-To: <f470f1cb-c0a9-054a-5b8e-68c95ed7340d@whitebeamsec.com>
> On 5 Jul 2022, at 11:34, Nathan Nye <nnye@whitebeamsec.com> wrote:
>
> All,
>
> I isolated the issue. When compiling binaries using gcc on Ubuntu 20.04 or below, the resulting binary does not have PIE - regardless of the -pie argument being passed to the compiler. Ubuntu 22.04 correctly reflects the default build flags being PIE and the binaries have PIE unless the arguments passed to gcc include -no-pie.
>
> Thanks,
> Nathan Nye
The problem is not in fact PIE, but rather that newer toolchain default to
bindnow. Using the provided example on
* Ubuntu 14 (glibc 2.19), Ubuntu 16 (glibc 2.23), and Ubuntu 18 (glibc 2.27)
$ gcc -Wall runevp.c -o runevp -Wl,-z,lazy
$ gcc -Wall -fPIC -shared -o auditlib.so auditlib.c
$ LD_AUDIT=./auditlib.so LD_BIND_NOT=1 LD_BIND_NOW=1 ./runevp
$
* And on Ubuntu 22.04 (glibc 2.35)
$ gcc -Wall runevp.c -o runevp -Wl,-z,lazy
$ gcc -Wall -fPIC -shared -o auditlib.so auditlib.c
$ LD_AUDIT=./auditlib.so LD_BIND_NOT=1 LD_BIND_NOW=1 ./runevp
symbol binding for ‘execvp'
On glibc 2.34 we now see a bind-now la_symbind event, different than
previous version. If you build with -Wl,-z,lazy we will see the previous
behavior where la_symbind will be called on each symbol resolution.
Now for LD_BIND_NOT and bind-now, I think this is the correct behavior:
we need to always update the GOT entry since runtime won’t setup a
lazy resolution PLT entry (symbols resolution is always setup at
startup phase). Otherwise we will need to add a hack similar to
LD_PROFILE and I really don’t think this is the best strategy.
>
> On 7/4/22 3:31 PM, Nathan Nye wrote:
>> +Adhemerval
>>
>> Hi Adhemerval,
>>
>> I think you may know the relevant source best if this issue exists. Your feedback would be really valuable if you're able to test it.
>>
>> Very respectfully,
>> Nathan Nye
>>
>> On 7/4/22 3:14 PM, Nathan Nye wrote:
>>> Good afternoon,
>>>
>>> I'm reviewing what could be a regression in LD_BIND_NOT's functionality in glibc 2.35 on ARM architectures (there were a few recent ARM audit changes). Symbol binding only occurs a single time on glibc 2.35/ARM, even when LD_BIND_NOT is enabled. I've tested:
>>> • Ubuntu 22.04 x86_64 glibc 2.35
>>> • Ubuntu 20.04 ARM glibc 2.34
>>> • Ubuntu 22.04 ARM glibc 2.35
>>> I could use a second pair of eyes on this issue to verify it exists. Here is the test case I cobbled together, please excuse the poor C code I wrote while testing: https://pastebin.com/raw/HSSYjemj
>>>
>>> I've also attached the test case to this email. Thanks!
>>>
>>> Very respectfully,
>>> Nathan Nye
>>
>
> <OpenPGP_0xCB7269934F16882E.asc>
prev parent reply other threads:[~2022-07-05 17:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-04 19:14 Nathan Nye
2022-07-04 19:31 ` Nathan Nye
2022-07-05 14:34 ` Nathan Nye
2022-07-05 17:04 ` Adhemerval Zanella [this message]
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