Re: [PATCH vfs v2] bpf: Allow bpf_d_path() from filp_close_sync()

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 2026-10-21 1:54 a.m., Christian Brauner wrote:
> On Fri, Sep 25, 2026 at 02:03:47PM -0700, Ihor Solodrai wrote:
>> The d_path selftest closes its descriptors with close_range() so that
>> its fentry program on filp_close() runs. The vfs commit
>> c1ed65ea167b ("fs: make close_range() synchronous") switched
>> close_range() to filp_close_sync(), so the program still attaches but
>> is never called:
>>
>>    test_d_path_basic:FAIL:close trampoline for filp_close was not called
>>
>> With that series, close(), close_range() and the closes on exec and
>> exit all go through filp_close_sync(). Few paths still reach
>> filp_close(), dup2() being one of them, so a program on filp_close()
>> no longer sees most file closes.
>>
>> Allow bpf_d_path() from filp_close_sync(), but only from fentry.
>> filp_close_sync() drops the last file reference inline, so by the time
>> an fexit program runs, file->f_path may already be freed, with no RCU
>> delay for NORCU dentries such as pipes and sockets.
>>
>> Attach the selftest program to filp_close_sync() and keep triggering
>> it with close_range().
>>
>> Add a test rejecting bpf_d_path() from fexit/filp_close_sync.
>>
>> Assisted-by: LLM
>> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
>>
>> ---
> 
> This seems fine to me. Sashiko has some comments though.
> Maybe go through them and resend as necessary.

I looked at them when sashiko replied and dismissed.
Should've commented.

I'll respin anyways to rebase, it's been a month.

Thanks for taking a look.