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<1c0ec9e2c7498db4c44087663b413383e3a13b4d.camel@linux.ibm.com> Subject: Re: [PATCH 1/3] s390/pci: Adjust alignment in insn trace From: Niklas Schnelle To: Gerd Bayer , sashiko-reviews@lists.linux.dev Cc: Heiko Carstens , linux-s390@vger.kernel.org, Christian Borntraeger , Vasily Gorbik , Alexander Gordeev In-Reply-To: <9d1fe490bc472cf9f77407afbbd7dae2c4cd7e6a.camel@linux.ibm.com> References: <20261007-rpcit_trcfh_upstream-v1-0-8a2718cfb90b@linux.ibm.com> <20261007-rpcit_trcfh_upstream-v1-1-8a2718cfb90b@linux.ibm.com> <9d1fe490bc472cf9f77407afbbd7dae2c4cd7e6a.camel@linux.ibm.com> Autocrypt: addr=schnelle@linux.ibm.com; prefer-encrypt=mutual; keydata=mQINBGHm3M8BEAC+MIQkfoPIAKdjjk84OSQ8erd2OICj98+GdhMQpIjHXn/RJdCZLa58k /ay5x0xIHkWzx1JJOm4Lki7WEzRbYDexQEJP0xUia0U+4Yg7PJL4Dg/W4Ho28dRBROoJjgJSLSHwc 3/1pjpNlSaX/qg3ZM8+/EiSGc7uEPklLYu3gRGxcWV/944HdUyLcnjrZwCn2+gg9ncVJjsimS0ro/ 2wU2RPE4ju6NMBn5Go26sAj1owdYQQv9t0d71CmZS9Bh+2+cLjC7HvyTHKFxVGOznUL+j1a45VrVS 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malwarescore=0 clxscore=1015 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610070058 On Wed, 2026-10-07 at 15:10 +0200, Gerd Bayer wrote: > On Wed, 2026-10-07 at 11:14 +0000, sashiko-bot@kernel.org wrote: > > Thank you for your contribution! Sashiko AI review found 1 potential is= sue(s) to consider: > > - [Medium] s390/pci: info leak of kernel stack memory in trace buffer d= ue to unnamed bit-fields > > -- > >=20 > > commit 9eddce7825c1b38a4a78855744726217e301528b > > Author: Gerd Bayer > >=20 --- snip --- > >=20 > > [Severity: Medium] > > Does this change unintentionally leak kernel stack memory into the s390= dbf > > debug trace ring buffer? > >=20 > > By using unnamed bit-fields for padding, these fields are explicitly > > excluded from zero-initialization when using a designated initializer. > >=20 > > When zpci_err_insn_req() in arch/s390/pci/pci_insn.c initializes this > > structure on the stack without an explicit memset(), the unnamed paddin= g > > bytes retain their uninitialized stack memory: > >=20 > > static inline void zpci_err_insn_req(...) > > { > > struct zpci_err_insn_data data =3D { > > .insn =3D insn, .cc =3D cc, .status =3D status, > > .req =3D req, .offset =3D offset}; > >=20 > > zpci_err_hex_level(lvl, &data, sizeof(data)); > > } > >=20 > > The subsequent call to zpci_err_hex_level() will copy the entire 32-byt= e > > structure to the trace buffer, exposing 13 bytes of uninitialized stack > > data. > >=20 > > Will this also defeat the goal of having clean traces for humans, since > > the hex dumps will contain random stack data instead of zeroes? >=20 >=20 > Alright, according to some research [1][2] unnamed bit-fields are not > guaranteed to be zero-initialized. I'll provide dummy-names for the > padding fields in the next iteration. Agree and to be honest I do like named reserved fields better for readability too. Other than this issue this all looks good to me and should definitely make the hex_error easier to read. Thanks, Niklas > >=20