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

Guenter Roeck
2024-01-26T23:55:06Z

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

> maintainers of the driver and subsystem in question.
>
> Cheers,
> Nathan