Am 28.10.22 um 18:36 schrieb Kees Cook:
On Fri, Oct 28, 2022 at 09:18:39AM +0200, Christian König wrote:
Am 28.10.22 um 07:10 schrieb Paulo Miguel Almeida:
One-element arrays are deprecated, and we are replacing them with
flexible array members instead. So, replace one-element array with
flexible-array member in struct _ATOM_FAKE_EDID_PATCH_RECORD and
refactor the rest of the code accordingly.
This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -fstrict-flex-arrays=3 [1].
Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FKSPP%2Flinux%2Fissues%2F79&data=05%7C01%7Cchristian.koenig%40amd.com%7C600d3657cbe441ae969d08dab9028c1c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638025717852262567%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=h78kYVA3ee9fDDwD5XGNgYJuUAZtBitVpk2354cOLO4%3D&reserved=0
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Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fbugzilla%2Fshow_bug.cgi%3Fid%3D101836&data=05%7C01%7Cchristian.koenig%40amd.com%7C600d3657cbe441ae969d08dab9028c1c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638025717852262567%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=LJB4Rs1xOE82UpLbqtZOgPgi7OmvR02T9fikpKamdiY%3D&reserved=0 [1]
I'm not sure if that's a good idea. We had multiple attempts to refactor
this now and it always caused a regression.
Additional to that the header in question came from our BIOS team and isn't
following Linux styles in general.
Alex what do you think?
Fake flexible arrays (i.e. 1-element arrays) are deprecated in Linux[1]
(and, frankly, deprecated in C since 1999 and even well before then given
the 0-sized extension that was added in GCC), so we can't continue to
bring them into kernel sources. Their use breaks both compile-time and
run-time bounds checking efforts, etc.
I'm perfectly aware of that. The issue is that we have tried to fix this
multiple times now and reverted back to the original behavior because
some user with a 10-15 year old hardware complained that it broke his
system.
We can't really test every hw generation of the last 15 years for
regressions.
All that said, converting away from them can be tricky, and I think such
conversions need to explicitly show how they were checked for binary
differences[2].
Oh, that's a great idea! Yes, if this can be guaranteed then the change
is obviously perfectly ok.
Thanks,
Christian.
Paulo, can you please check for deltas and report your findings in the
commit log? Note that add struct_size() use in the same patch may result
in binary differences, so for more complex cases, you may want to split
the 1-element conversion from the struct_size() conversions.
-Kees
[1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.kernel.org%2Fprocess%2Fdeprecated.html%23zero-length-and-one-element-arrays&data=05%7C01%7Cchristian.koenig%40amd.com%7C600d3657cbe441ae969d08dab9028c1c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638025717852262567%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=6v1qt3zMrSTFDgnF9TO3aurqvG1fPjH2grRu47e2tEA%3D&reserved=0
[2] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Foutflux.net%2Fblog%2Farchives%2F2022%2F06%2F24%2Ffinding-binary-differences%2F&data=05%7C01%7Cchristian.koenig%40amd.com%7C600d3657cbe441ae969d08dab9028c1c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638025717852262567%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=g3yCIXBAD0OJwK5EdxRfJVeSBevbA1WOeyFM%2BiZC%2F%2FM%3D&reserved=0
