From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 05719168CF for ; Mon, 8 May 2023 11:17:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 608E9C433EF; Mon, 8 May 2023 11:17:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1683544627; bh=Be0Gr0J6u7pMKBcJ2cMXMPg950I8kiIaY3AvJN1XAbY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zKbNIe9I20HB4UbGcv0FxzPcB5xIrgCepEYfgKC8MJ7U7IT+Anp+CqZLnBWv5k8UA YOdT2RnQsyEs9c3yt7k5EHZT/l49ToISjbWmop8G0AW5ewj7gSbQINhWtGSj5zCCL+ eTr69j4NlY4l1ornmpLZYRSlV7KDjHsDGjTCWM0s= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Florian Westphal , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Sasha Levin Subject: [PATCH 6.3 471/694] bpf: Fix race between btf_put and btf_idr walk. Date: Mon, 8 May 2023 11:45:06 +0200 Message-Id: <20230508094449.085726884@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230508094432.603705160@linuxfoundation.org> References: <20230508094432.603705160@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Alexei Starovoitov [ Upstream commit acf1c3d68e9a31f10d92bc67ad4673cdae5e8d92 ] Florian and Eduard reported hard dead lock: [ 58.433327] _raw_spin_lock_irqsave+0x40/0x50 [ 58.433334] btf_put+0x43/0x90 [ 58.433338] bpf_find_btf_id+0x157/0x240 [ 58.433353] btf_parse_fields+0x921/0x11c0 This happens since btf->refcount can be 1 at the time of btf_put() and btf_put() will call btf_free_id() which will try to grab btf_idr_lock and will dead lock. Avoid the issue by doing btf_put() without locking. Fixes: 3d78417b60fb ("bpf: Add bpf_btf_find_by_name_kind() helper.") Fixes: 1e89106da253 ("bpf: Add bpf_core_add_cands() and wire it into bpf_core_apply_relo_insn().") Reported-by: Florian Westphal Reported-by: Eduard Zingerman Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Tested-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/20230421014901.70908-1-alexei.starovoitov@gmail.com Signed-off-by: Sasha Levin --- kernel/bpf/btf.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 3140a7881665d..46bce5577fb48 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -572,8 +572,8 @@ static s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p) *btf_p = btf; return ret; } - spin_lock_bh(&btf_idr_lock); btf_put(btf); + spin_lock_bh(&btf_idr_lock); } spin_unlock_bh(&btf_idr_lock); return ret; @@ -8245,12 +8245,10 @@ bpf_core_find_cands(struct bpf_core_ctx *ctx, u32 local_type_id) btf_get(mod_btf); spin_unlock_bh(&btf_idr_lock); cands = bpf_core_add_cands(cands, mod_btf, btf_nr_types(main_btf)); - if (IS_ERR(cands)) { - btf_put(mod_btf); + btf_put(mod_btf); + if (IS_ERR(cands)) return ERR_CAST(cands); - } spin_lock_bh(&btf_idr_lock); - btf_put(mod_btf); } spin_unlock_bh(&btf_idr_lock); /* cands is a pointer to kmalloced memory here if cands->cnt > 0 -- 2.39.2