From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A7E64496915 for ; Tue, 14 Jul 2026 15:57:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784044656; cv=none; b=Wmw58Cjlhcg5rVDN8hFXgtBvYEI+QwdZIywgjK9RiFV0w4e4I5nbuJiHMA0ygNxrz01ud0rPdsQDpaB1d8+NzmwTOSGhQ3enGTRPRuri63CDesK+1tdZm/QKGmUs0a5WpF9J5h3Z6vu/VV0LKhDBb0GdUDnFL3zgLnCR+JacaSA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784044656; c=relaxed/simple; bh=X7LX/JIfOkMIuQ/tGoX3jrl1sF+SenmAoSFnxQrL4pE=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=bGbSIn8OT49Zr6rr2CPlniayextRUXOuBc/bQ8Ia+TmAzsJlPB0vPGPQ53xvnvg8kKZwdZeXxvn7OPQq+Ci8qL/CecaaC4eRQ6GM0/JdxvbXxnEU3DSBbOA4Rk6vbfNQx/i1675NBDFFUUnQBWYgwtrkBI5mM4G8fB1AngAKBng= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=KXqCnKPq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="KXqCnKPq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA9051F000E9; Tue, 14 Jul 2026 15:57:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784044655; bh=nhqUXTfRQ6pCkziiWdjrl2yaU6LQyDaKgeBgRzkgEzc=; h=Subject:To:Cc:From:Date; b=KXqCnKPqS8Ra88iaBwCqqsrGtcNpzjGXVzCVnCXRWxtBRjwh6hOzhyTL4nDR44lyk vGjA0i11Vc0zBGUEr4Q+aR4kVpEt3VcV5X0i5MWoCLeh32vMOQa9HCzOND5GRNYSW+ NHe2J52lmUtXA6x/RA1GFXTuq15IFV5PKlBzlwAs= Subject: FAILED: patch "[PATCH] bpf: Allow LPM map access from sleepable BPF programs" failed to apply to 6.18-stable tree To: vlad.wing@gmail.com,ast@kernel.org,emil@etsalapatis.com Cc: From: Date: Tue, 14 Jul 2026 17:57:29 +0200 Message-ID: <2026071429-contort-navy-4802@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 2f884d371fafea137afea504d49ee4a7c8d7985b # git commit -s git send-email --to '' --in-reply-to '2026071429-contort-navy-4802@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 2f884d371fafea137afea504d49ee4a7c8d7985b Mon Sep 17 00:00:00 2001 From: Vlad Poenaru Date: Tue, 9 Jun 2026 06:55:57 -0700 Subject: [PATCH] bpf: Allow LPM map access from sleepable BPF programs trie_lookup_elem() annotates its rcu_dereference_check() walks with only rcu_read_lock_bh_held(). Because rcu_dereference_check(p, c) resolves to "c || rcu_read_lock_held()", this passes for XDP/NAPI and classic RCU readers but fails for sleepable BPF programs, which enter via __bpf_prog_enter_sleepable() and hold only rcu_read_lock_trace(). trie_update_elem() and trie_delete_elem() have the same problem in a different form: they walk the trie with plain rcu_dereference(), which asserts rcu_read_lock_held() unconditionally. Both are reachable from sleepable BPF programs via the bpf_map_update_elem / bpf_map_delete_elem helpers, and from the syscall path under classic rcu_read_lock(). In the writer paths the trie is actually protected by trie->lock (an rqspinlock taken across the walk); we never relied on the RCU read-side lock to keep nodes alive there. A sleepable LSM hook that ends up touching an LPM trie therefore triggers lockdep on debug kernels: ============================= WARNING: suspicious RCU usage 7.1.0-... Tainted: G E ----------------------------- kernel/bpf/lpm_trie.c:249 suspicious rcu_dereference_check() usage! 1 lock held by net_tests/540: #0: (rcu_tasks_trace_srcu_struct){....}-{0:0}, at: __bpf_prog_enter_sleepable+0x26/0x280 Call Trace: dump_stack_lvl lockdep_rcu_suspicious trie_lookup_elem bpf_prog_..._enforce_security_socket_connect bpf_trampoline_... security_socket_connect __sys_connect do_syscall_64 This is lockdep-only -- no UAF, since Tasks Trace RCU does serialize against the trie's reclaim path -- but it spams the console once per distinct callsite on every debug kernel running a sleepable BPF LSM that touches an LPM trie, which is increasingly common. For the lookup path, switch the rcu_dereference_check() annotation from rcu_read_lock_bh_held() to bpf_rcu_lock_held(), which accepts all three contexts (classic, BH, Tasks Trace). Other map types already follow this convention. For trie_update_elem() and trie_delete_elem(), annotate the walks as rcu_dereference_protected(*p, 1) -- matching trie_free() in the same file -- since trie->lock is held across the walk. rqspinlock has no lockdep_map, so the predicate degenerates to '1' rather than lockdep_is_held(&trie->lock); the protection is real but not machine-verifiable. trie_get_next_key() also uses bare rcu_dereference() but is reachable only from the BPF syscall, which holds classic rcu_read_lock() before dispatching, so it is left untouched. Fixes: 694cea395fde ("bpf: Allow RCU-protected lookups to happen from bh context") Cc: stable@vger.kernel.org Signed-off-by: Vlad Poenaru Reviewed-by: Emil Tsalapatis Link: https://lore.kernel.org/r/20260609135558.193287-2-vlad.wing@gmail.com Signed-off-by: Alexei Starovoitov diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 0f57608b385d..4d6f25db9ba1 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -246,7 +246,7 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) /* Start walking the trie from the root node ... */ - for (node = rcu_dereference_check(trie->root, rcu_read_lock_bh_held()); + for (node = rcu_dereference_check(trie->root, bpf_rcu_lock_held()); node;) { unsigned int next_bit; size_t matchlen; @@ -280,7 +280,7 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) */ next_bit = extract_bit(key->data, node->prefixlen); node = rcu_dereference_check(node->child[next_bit], - rcu_read_lock_bh_held()); + bpf_rcu_lock_held()); } if (!found) @@ -359,7 +359,7 @@ static long trie_update_elem(struct bpf_map *map, */ slot = &trie->root; - while ((node = rcu_dereference(*slot))) { + while ((node = rcu_dereference_protected(*slot, 1))) { matchlen = longest_prefix_match(trie, node, key); if (node->prefixlen != matchlen || @@ -482,7 +482,7 @@ static long trie_delete_elem(struct bpf_map *map, void *_key) trim = &trie->root; trim2 = trim; parent = NULL; - while ((node = rcu_dereference(*trim))) { + while ((node = rcu_dereference_protected(*trim, 1))) { matchlen = longest_prefix_match(trie, node, key); if (node->prefixlen != matchlen ||