From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE1641922FD for ; Mon, 27 Oct 2025 16:15:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.185 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761581720; cv=none; b=oBQ+xrD0apC76eAsyOHM/G1xo6zSSxAIzZQVlswje/oydTkW8OM6lBAYzOSLoSiBhFuOC/PqCmajeiue5XdlAJPuacK90o8o0Dn2LNQ7WtisTC8PobFY8ZsYnyoihF4cd4nkxI7oUsNJtYDPTI+yy45TxIt+nbudfrZ67bfdT4Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761581720; c=relaxed/simple; bh=hRAxd+FkwQLgGfPsQjGN8X1beEfzKDTTEusJws9tP+M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nXVee3hzjCHbKL3LcBjgNNLplQmEfBNkn3KuvMFhXqua9ELvjCod0G4b1/b/yzKafqV5mgbEh7CDHXmeh5XOLdyFnLKAxDZGDPKKeQoroEDCHRNVxN4bHV2z0JpGCOr+harsDzojwqrFGVh3A28p1hV5p5E2EdeNY69Gwo92D2k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=pP17JoL8; arc=none smtp.client-ip=91.218.175.185 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="pP17JoL8" Message-ID: <377791b5-2294-4ced-a0d3-918c7e078b2b@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761581714; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M8JTohyHajSv2yqB/P5lZqmQ7D54tX4fjYrvkezQRS8=; b=pP17JoL8ihlLdX0Mz1k2oHA6DwL8LdNxl1/o3ETBf0jy2VE2Y37sbSWZW9xW+nzbsmUiWj CwhBwBJIDwTqp3AdOPn+Ge9joU1w7Mvqi8gzomjzTcPr9ufDS/yFVa/cOZpvtLw+yJtAYz oJPHvPUnU5MYinrHykT44hPQ/pnrGro= Date: Tue, 28 Oct 2025 00:15:03 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf v3 3/4] bpf: Free special fields when update local storage maps To: Amery Hung Cc: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, memxor@gmail.com, linux-kernel@vger.kernel.org, kernel-patches-bot@fb.com References: <20251026154000.34151-1-leon.hwang@linux.dev> <20251026154000.34151-4-leon.hwang@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Leon Hwang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Hi Amery, On 2025/10/27 23:44, Amery Hung wrote: > On Sun, Oct 26, 2025 at 8:41 AM Leon Hwang wrote: >> >> When updating local storage maps with BPF_F_LOCK on the fast path, the >> special fields were not freed after being replaced. This could cause >> memory referenced by BPF_KPTR_{REF,PERCPU} fields to be held until the >> map gets freed. >> >> Similarly, on the other path, the old sdata's special fields were never >> freed regardless of whether BPF_F_LOCK was used, causing the same issue. >> >> Fix this by calling 'bpf_obj_free_fields()' after >> 'copy_map_value_locked()' to properly release the old fields. >> >> Fixes: 9db44fdd8105 ("bpf: Support kptrs in local storage maps") >> Signed-off-by: Leon Hwang >> --- >> kernel/bpf/bpf_local_storage.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c >> index b931fbceb54da..8e3aea4e07c50 100644 >> --- a/kernel/bpf/bpf_local_storage.c >> +++ b/kernel/bpf/bpf_local_storage.c >> @@ -609,6 +609,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, >> if (old_sdata && selem_linked_to_storage_lockless(SELEM(old_sdata))) { >> copy_map_value_locked(&smap->map, old_sdata->data, >> value, false); >> + bpf_obj_free_fields(smap->map.record, old_sdata->data); > > [ ... ] > >> return old_sdata; >> } >> } >> @@ -641,6 +642,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, >> if (old_sdata && (map_flags & BPF_F_LOCK)) { >> copy_map_value_locked(&smap->map, old_sdata->data, value, >> false); >> + bpf_obj_free_fields(smap->map.record, old_sdata->data); > > The one above and this make sense. Thanks for fixing it. > Thanks for your review. >> selem = SELEM(old_sdata); >> goto unlock; >> } >> @@ -654,6 +656,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, >> >> /* Third, remove old selem, SELEM(old_sdata) */ >> if (old_sdata) { >> + bpf_obj_free_fields(smap->map.record, old_sdata->data); > > Is this really needed? bpf_selem_free_list() later should free special > fields in this selem. > Yes, it’s needed. The new selftest confirms that the special fields are not freed when updating a local storage map. Also, bpf_selem_unlink_storage_nolock() doesn’t invoke bpf_selem_free_list(), unlike bpf_selem_unlink_storage(). So we need to call bpf_obj_free_fields() here explicitly to free those fields. Thanks, Leon [...]