Re: [git pull] d_revalidate pile

Sasha Levin
2025-01-27T22:32:20Z

[ Adding in the LKFT folks ]

On Mon, Jan 27, 2025 at 08:38:50PM +0000, Mark Brown wrote:
>On Mon, Jan 27, 2025 at 11:12:11AM -0800, Linus Torvalds wrote:
>> On Mon, 27 Jan 2025 at 09:19, Sasha Levin <sashal@kernel.org> wrote:
>
>> > With this pulled on top of Linus's tree, LKFT is managing to trigger
>> > kfence warnings:
>
>> > <3>[ 62.180289] BUG: KFENCE: out-of-bounds read in d_same_name+0x4c/0xd0
>> > <3>[ 62.180289]
>> > <3>[ 62.182647] Out-of-bounds read at 0x00000000eedd4b55 (64B right of kfence-#174):
>> > <4>[ 62.184178] d_same_name+0x4c/0xd0
>
>> Bah. I've said this before, but I really wish LKFT would use debug
>> builds and run the warnings through scripts/decode_stacktrace.sh.
>
>> Getting filenames and line numbers (and inlining information!) for
>> stack traces can be really really useful.
>
>> I think you are using KernelCI builds (at least that was the case last
>> time), and apparently they are non-debug builds. And that's possibly
>> due to just resource issues (the debug info does take a lot more disk
>> space and makes link times much longer too). So it might not be easily
>> fixable.
>
>They're not, they're using their own builds done with their tuxsuite
>service which is a cloud front end for their tuxmake tool, that does
>have the ability to save the vmlinux. Poking around the LKFT output it
>does look like they're doing that for the LKFT builds:
>
> https://qa-reports.linaro.org/lkft/sashal-linus-next/build/v6.13-rc7-8584-gd4639f3659ae/testrun/27027254/suite/build/test/gcc-13-tinyconfig/details/
> https://storage.tuxsuite.com/public/linaro/lkft/builds/2sDW1jDhjHPNl1XNezFhsjSlvpI/
>
>so hopefully the information is all there and it's just a question of
>people doing the decode when reporting issues from LKFT.

My understanding was that becuase CONFIG_DEBUG_INFO_NONE=y is set, we
actually don't have enough info to resolve line numbers.

I've tried running decode_stacktrace.sh on the vmlinux image linked
above, and indeed we can't get line numbers.

--
Thanks,
Sasha