Re: [PATCH vfs v3] bpf: Allow bpf_d_path() from filp_close_sync()

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

On 10/21/26 1:13 PM, Ihor Solodrai wrote:
> The d_path selftest closes its descriptors with close_range() so that
> its fentry program on filp_close() runs.
> 
> Commit 056069eb2b66 ("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
> Fixes: 056069eb2b66 ("fs: make close_range() synchronous")
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>

Christian,

Just in case you pay attention to BPF CI signals, they are red for
this patch because commit 056069eb2b66 is not in bpf-next yet.

Thanks.

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