Re: Re: [PATCH 5.10 000/286] 5.10.209-rc1 review

zhenwei pi
2024-01-29T09:58:14Z

On 1/29/24 16:46, Michael S. Tsirkin wrote:
> On Fri, Jan 26, 2024 at 03:55:02PM -0800, Guenter Roeck wrote:
>> On 1/26/24 14:35, Nathan Chancellor wrote:
>>> (slimming up the CC list, I don't think this is too relevant to the
>>> wider stable community)
>>>
>>> On Fri, Jan 26, 2024 at 01:01:15PM -0800, Guenter Roeck wrote:
>>>> On 1/26/24 12:34, Nathan Chancellor wrote:
>>>>> On Fri, Jan 26, 2024 at 10:17:23AM -0800, Guenter Roeck wrote:
>>>>>> On 1/26/24 09:51, Greg Kroah-Hartman wrote:
>>>>>>> On Fri, Jan 26, 2024 at 08:46:42AM -0800, Guenter Roeck wrote:
>>>>>>>> On 1/22/24 15:55, Greg Kroah-Hartman wrote:
>>>>>>>>> This is the start of the stable review cycle for the 5.10.209 release.
>>>>>>>>> There are 286 patches in this series, all will be posted as a response
>>>>>>>>> to this one. If anyone has any issues with these being applied, please
>>>>>>>>> let me know.
>>>>>>>>>
>>>>>>>>> Responses should be made by Wed, 24 Jan 2024 23:56:49 +0000.
>>>>>>>>> Anything received after that time might be too late.
>>>>>>>>>
>>>>>>>> [ ... ]
>>>>>>>>
>>>>>>>>> zhenwei pi <pizhenwei@bytedance.com>
>>>>>>>>> virtio-crypto: implement RSA algorithm
>>>>>>>>>
>>>>>>>>
>>>>>>>> Curious: Why was this (and its subsequent fixes) backported to v5.10.y ?
>>>>>>>> It is quite beyond a bug fix. Also, unless I am really missing something,
>>>>>>>> the series (or at least this patch) was not applied to v5.15.y, so we now
>>>>>>>> have functionality in v5.10.y which is not in v5.15.y.
>>>>>>>
>>>>>>> See the commit text, it was a dependency of a later fix and documented
>>>>>>> as such.
>>>>>>>
>>>>>>> Having it in 5.10 and not 5.15 is a bit odd, I agree, so patches are
>>>>>>> gladly accepted :)
>>>>>>>
>>>>>>
>>>>>> We reverted the entire series from the merge because it results in a build
>>>>>> failure for us.
>>>>>>
>>>>>> In file included from /home/groeck/src/linux-chromeos/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c:10:
>>>>>> In file included from /home/groeck/src/linux-chromeos/include/linux/mpi.h:21:
>>>>>> In file included from /home/groeck/src/linux-chromeos/include/linux/scatterlist.h:5:
>>>>>> In file included from /home/groeck/src/linux-chromeos/include/linux/string.h:293:
>>>>>> /home/groeck/src/linux-chromeos/include/linux/fortify-string.h:512:4: error: call to __read_overflow2_field declared with 'warning' attribute: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror,-Wattribute-warning]
>>>>>> __read_overflow2_field(q_size_field, size);
>>>>>
>>>>> For what it's worth, this is likely self inflicted for chromeos-5.10,
>>>>> which carries a revert of commit eaafc590053b ("fortify: Explicitly
>>>>> disable Clang support") as commit c19861d34c003 ("CHROMIUM: Revert
>>>>> "fortify: Explicitly disable Clang support""). I don't see the series
>>>>> that added proper support for clang to fortify in 5.18 that ended with
>>>>> commit 281d0c962752 ("fortify: Add Clang support") in that ChromeOS
>>>>> branch, so this seems somewhat expected.
>>>>>
>>>>
>>>> That explains that ;-). I don't mind if the patches stay in v5.10.y,
>>>> we have them reverted anyway.
>>>>
>>>> The revert was a pure process issue, as you may see when looking into
>>>> commit c19861d34c003, so, yes, I agree that it is self-inflicted damage.
>>>> Still, that doesn't explain why the problem exists in 5.18+.
>>>>
>>>>>> I also see that upstream (starting with 6.1) when trying to build it with clang,
>>>>>> so I guess it is one of those bug-for-bug compatibility things. I really have
>>>>>> no idea what causes it, or why we don't see the problem when building
>>>>>> chromeos-6.1 or chromeos-6.6, but (so far) only with chromeos-5.10 after
>>>>>> merging 5.10.209 into it. Making things worse, the problem isn't _always_
>>>>>> seen. Sometimes I can compile the file in 6.1.y without error, sometimes not.
>>>>>> I have no idea what triggers the problem.
>>>>>
>>>>> Have a .config that reproduces it on upstream? I have not personally
>>>>> seen this warning in my build matrix nor has our continuous-integration
>>>>> matrix (I don't see it in the warning output at the bottom but that
>>>>> could have missed something for some reason) in 6.1:
>>>>>
>>>>
>>>> The following command sequence reproduces the problem for me with all stable
>>>> branches starting with 5.18.y (plus mainline).
>>>>
>>>> rm -rf /tmp/crypto-build
>>>> mkdir /tmp/crypto-build
>>>> make -j CC=clang-15 mrproper >/dev/null 2>&1
>>>> make -j O=/tmp/crypto-build CC=clang-15 allmodconfig >/dev/null 2>&1
>>>> make -j O=/tmp/crypto-build W=1 CC=clang-15 drivers/crypto/virtio/virtio_crypto_akcipher_algs.o
>>>>
>>>> I tried clang versions 14, 15, and 16. This is with my home system running
>>>> Ubuntu 22.04, no ChromeOS or Google specifics/internals involved. For clang-15,
>>>> the version is
>>>>
>>>> Ubuntu clang version 15.0.7
>>>> Target: x86_64-pc-linux-gnu
>>>> Thread model: posix
>>>> InstalledDir: /usr/bin
>>>
>>> Okay interesting, this warning is hidden behind W=1, which our CI does
>>> not test with. Looks like it has been that way since the introduction of
>>> these checks in f68f2ff91512 ("fortify: Detect struct member overflows
>>> in memcpy() at compile-time").
>>>
>>
>> Interestingly the warning is seen in chromeos-5.10, without this patch,
>> and without W=1. I guess that must have to do with the revert which is
>> finally biting us.
>>
>>> I think this is a legitimate warning though. It is complaining about the
>>> second memcpy() in virtio_crypto_alg_akcipher_init_session():
>>>
>>> memcpy(&ctrl->u, para, sizeof(ctrl->u));
>>>
>>> where ctrl is:
>>>
>>> struct virtio_crypto_op_ctrl_req {
>>> struct virtio_crypto_ctrl_header header; /* 0 16 */
>>> union {
>>> struct virtio_crypto_sym_create_session_req sym_create_session; /* 16 56 */
>>> struct virtio_crypto_hash_create_session_req hash_create_session; /* 16 56 */
>>> struct virtio_crypto_mac_create_session_req mac_create_session; /* 16 56 */
>>> struct virtio_crypto_aead_create_session_req aead_create_session; /* 16 56 */
>>> struct virtio_crypto_akcipher_create_session_req akcipher_create_session; /* 16 56 */
>>> struct virtio_crypto_destroy_session_req destroy_session; /* 16 56 */
>>> __u8 padding[56]; /* 16 56 */
>>> } u; /* 16 56 */
>>> union {
>>> struct virtio_crypto_sym_create_session_req sym_create_session; /* 0 56 */
>>> struct virtio_crypto_hash_create_session_req hash_create_session; /* 0 56 */
>>> struct virtio_crypto_mac_create_session_req mac_create_session; /* 0 56 */
>>> struct virtio_crypto_aead_create_session_req aead_create_session; /* 0 56 */
>>> struct virtio_crypto_akcipher_create_session_req akcipher_create_session; /* 0 56 */
>>> struct virtio_crypto_destroy_session_req destroy_session; /* 0 56 */
>>> __u8 padding[56]; /* 0 56 */
>>> };
>>>
>>>
>>> /* size: 72, cachelines: 2, members: 2 */
>>> /* last cacheline: 8 bytes */
>>> };
>>>
>>> (so size and p_size_field should be 56) and the type of the para
>>> parameter in virtio_crypto_alg_akcipher_init_session() is 'void *' but
>>> the para passed by reference to
>>> virtio_crypto_alg_akcipher_init_session() in virtio_crypto_rsa_set_key()
>>> has a type of 'struct virtio_crypto_akcipher_session_para':
>>>
>>> struct virtio_crypto_akcipher_session_para {
>>> __le32 algo; /* 0 4 */
>>> __le32 keytype; /* 4 4 */
>>> __le32 keylen; /* 8 4 */
>>> union {
>>> struct virtio_crypto_rsa_session_para rsa; /* 12 8 */
>>> struct virtio_crypto_ecdsa_session_para ecdsa; /* 12 8 */
>>> } u; /* 12 8 */
>>> union {
>>> struct virtio_crypto_rsa_session_para rsa; /* 0 8 */
>>> struct virtio_crypto_ecdsa_session_para ecdsa; /* 0 8 */
>>> };
>>>
>>>
>>> /* size: 20, cachelines: 1, members: 4 */
>>> /* last cacheline: 20 bytes */
>>> };
>>>
>>> (so q_size_field would be 20 if clang were able to do inlining to see
>>> through the 'void *'...?), which would result in the
>>>
>>> __compiletime_lessthan(q_size_field, size)
>>>
>>> check succeeding and triggering the warning because 20 < 56, so it does
>>> seem like there is an overread of the source buffer here? Adding the
>>
>> Looks like it; I think either the passed 'para' should be of type
>> virtio_crypto_akcipher_create_session_req() or it should only copy
>> sizeof(struct virtio_crypto_akcipher_session_para) bytes.
>>
>> Anyway, how did you find that ? Is there a magic trick to find the
>> actual code causing the warning ? I am asking because we had seen
>> similar warnings before, and it would help to know how to find the
>> problematic code.
>>
>> Thanks,
>> Guenter
>
>
>
> Cc: zhenwei pi <pizhenwei@bytedance.com>
>
> Zhenwei I think you wrote most of the code here.
> Can you take a look please?
> Stack overflows are plus plus ungood.
>
>
>
>
>>> maintainers of the driver and subsystem in question.
>>>
>>> Cheers,
>>> Nathan
>

I can also reproduce this warning by commands on ubuntu-2204:
make -j CC=clang-14 mrproper >/dev/null 2>&1
make -j O=/tmp/crypto-build CC=clang-14 allmodconfig >/dev/null 2>&1
make -j O=/tmp/crypto-build W=1 CC=clang-14
drivers/crypto/virtio/virtio_crypto_akcipher_algs.o

so sorry on this issue, I think Guenter's suggestion is right(also test
by these commands), I'll send a fix later.

--
zhenwei pi