From patchwork Wed Dec 18 19:30:00 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin KaFai Lau X-Patchwork-Id: 13914085 X-Patchwork-Delegate: bpf@iogearbox.net Received: from out-176.mta0.migadu.com (out-176.mta0.migadu.com [91.218.175.176]) (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 3B4A31FC10F for ; Wed, 18 Dec 2024 19:30:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.176 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734550226; cv=none; b=Ho23/pmwPgOPtuuHrRhXe5H8b5Y4ZbmR9I0mfylnmrOmWzFlHgPGsM7NUOMPmsnIrAspdwO6KzygC7Axke4+p14131q1AKPs4zo764AQmxqiYw7INZguGM6wFWCJMOF2FOK6LndItw4aL2pNjEejRzt1OFS8TqIUjTvywhaJqhY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734550226; c=relaxed/simple; bh=5QvGOWYdp+BrUUiAlwRzCuhirLxoYLqN8wDrBFPMR1U=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=j9Pt2ON7WiH5gaILK5mrrfgZO4w4lm96U2Hy/EK7pZt9PPeVtDbCESq6ljEvm8bzpRiOVp/c2X9yLA8DfP4h7tVTcBdG1mrmafuLIHaGVOMSETs7bgSHfAzeEc6e3bQmxdx0DG9jn0pFaN2ZImeExoaR70iacMaNIkIfwdxCH2A= 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=MpZS+BR2; arc=none smtp.client-ip=91.218.175.176 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="MpZS+BR2" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1734550219; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=1Xt8n6wz13CrbEO3Owqi3Fdv44pPnG6RDuvQRBq0OAU=; b=MpZS+BR2m97s3t5+MvqxETV/5tZ0xNjo9eV7lQ/ZIcvqRA3XJQgKXhbQB4tdVvU6L1eHVr +QzyphS1gpCJw0YdE68OOEYOL9BWUbR6BIyhQHEGRrQ664n/Gpadgpup+sst6dFkjfNDz/ 3MKcTiGCo98aOMTswtsTZy43UAWBIwQ= From: Martin KaFai Lau To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@meta.com Subject: [PATCH bpf-next] bpf: bpf_local_storage: Always use bpf_mem_alloc in PREEMPT_RT Date: Wed, 18 Dec 2024 11:30:00 -0800 Message-ID: <20241218193000.2084281-1-martin.lau@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net From: Martin KaFai Lau In PREEMPT_RT, kmalloc(GFP_ATOMIC) is still not safe in non preemptible context. bpf_mem_alloc must be used in PREEMPT_RT. This patch is to enforce bpf_mem_alloc in the bpf_local_storage when CONFIG_PREEMPT_RT is enabled. [ 35.118559] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 [ 35.118566] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1832, name: test_progs [ 35.118569] preempt_count: 1, expected: 0 [ 35.118571] RCU nest depth: 1, expected: 1 [ 35.118577] INFO: lockdep is turned off. ... [ 35.118647] __might_resched+0x433/0x5b0 [ 35.118677] rt_spin_lock+0xc3/0x290 [ 35.118700] ___slab_alloc+0x72/0xc40 [ 35.118723] __kmalloc_noprof+0x13f/0x4e0 [ 35.118732] bpf_map_kzalloc+0xe5/0x220 [ 35.118740] bpf_selem_alloc+0x1d2/0x7b0 [ 35.118755] bpf_local_storage_update+0x2fa/0x8b0 [ 35.118784] bpf_sk_storage_get_tracing+0x15a/0x1d0 [ 35.118791] bpf_prog_9a118d86fca78ebb_trace_inet_sock_set_state+0x44/0x66 [ 35.118795] bpf_trace_run3+0x222/0x400 [ 35.118820] __bpf_trace_inet_sock_set_state+0x11/0x20 [ 35.118824] trace_inet_sock_set_state+0x112/0x130 [ 35.118830] inet_sk_state_store+0x41/0x90 [ 35.118836] tcp_set_state+0x3b3/0x640 There is no need to adjust the gfp_flags passing to the bpf_mem_cache_alloc_flags() which only honors the GFP_KERNEL. The verifier has ensured GFP_KERNEL is passed only in sleepable context. It has been an old issue since the first introduction of the bpf_local_storage ~5 years ago, so this patch targets the bpf-next. bpf_mem_alloc is needed to solve it, so the Fixes tag is set to the commit when bpf_mem_alloc was first used in the bpf_local_storage. Fixes: 08a7ce384e33 ("bpf: Use bpf_mem_cache_alloc/free in bpf_local_storage_elem") Reported-by: Alexei Starovoitov Signed-off-by: Martin KaFai Lau --- kernel/bpf/bpf_local_storage.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 7e6a0af0afc1..e94820f6b0cd 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -841,8 +841,12 @@ bpf_local_storage_map_alloc(union bpf_attr *attr, smap->elem_size = offsetof(struct bpf_local_storage_elem, sdata.data[attr->value_size]); - smap->bpf_ma = bpf_ma; - if (bpf_ma) { + /* In PREEMPT_RT, kmalloc(GFP_ATOMIC) is still not safe in non + * preemptible context. Thus, enforce all storages to use + * bpf_mem_alloc when CONFIG_PREEMPT_RT is enabled. + */ + smap->bpf_ma = IS_ENABLED(CONFIG_PREEMPT_RT) ? true : bpf_ma; + if (smap->bpf_ma) { err = bpf_mem_alloc_init(&smap->selem_ma, smap->elem_size, false); if (err) goto free_smap;