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 06BDA82C60; Tue, 29 Apr 2025 17:32:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745947978; cv=none; b=bbRlagEN5kbfgsYvtcUgEbcQDje3JdasteUm2d4/NRwqJxAoh6+qw44USchb1yKfqFRtHqlyqakqsmFEFQgG61psikupx5yQfUPUbwueTevaGwa3Na6mXY1Tl9s2eyryITNOeVu+ai2q+NyyzVMOOHF7ERMrcwKZC+O7bcgjcIU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745947978; c=relaxed/simple; bh=Vze6bYeuMALB0JmaSX8QKxSat5+gnc+i6Bda3f2mw/Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=paKUCuyk/QH5ERVByLbirMIIzOGKklYpPhzP3M03dHfM2M/oSxfJNvb/O0CeV4MCUaqI9f6JbvuJmxpJsfEZGtsXe2tiDxqgUAP6UStt89fE9/oFisPjhVD2jTEbxX2q26mf22jCOMTtyryWEJpFb0LTFFhG4DrKOlnBKO8Hsfc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CTK0wvPJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="CTK0wvPJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8BB38C4CEE3; Tue, 29 Apr 2025 17:32:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1745947977; bh=Vze6bYeuMALB0JmaSX8QKxSat5+gnc+i6Bda3f2mw/Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CTK0wvPJnRZqQgG5+ZsD6m1//y4S9MS6LSutZPTbV4cC8LLVRlm8Lm9DfgBF986xn biSIus4Tdv6z58M281eK4mZJeaWcrvOis/0nJSBcakfltYzAPcVbLkIMhay2DnLRcr SnDe2PHI+NCyPk5KLNAJrdyHSNQz34CCiMuWlb/4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vlad Poenaru , Yonghong Song , Martin KaFai Lau , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.12 159/280] bpf: Fix kmemleak warning for percpu hashmap Date: Tue, 29 Apr 2025 18:41:40 +0200 Message-ID: <20250429161121.624105327@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250429161115.008747050@linuxfoundation.org> References: <20250429161115.008747050@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yonghong Song [ Upstream commit 11ba7ce076e5903e7bdc1fd1498979c331b3c286 ] Vlad Poenaru reported the following kmemleak issue: unreferenced object 0x606fd7c44ac8 (size 32): backtrace (crc 0): pcpu_alloc_noprof+0x730/0xeb0 bpf_map_alloc_percpu+0x69/0xc0 prealloc_init+0x9d/0x1b0 htab_map_alloc+0x363/0x510 map_create+0x215/0x3a0 __sys_bpf+0x16b/0x3e0 __x64_sys_bpf+0x18/0x20 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x4b/0x53 Further investigation shows the reason is due to not 8-byte aligned store of percpu pointer in htab_elem_set_ptr(): *(void __percpu **)(l->key + key_size) = pptr; Note that the whole htab_elem alignment is 8 (for x86_64). If the key_size is 4, that means pptr is stored in a location which is 4 byte aligned but not 8 byte aligned. In mm/kmemleak.c, scan_block() scans the memory based on 8 byte stride, so it won't detect above pptr, hence reporting the memory leak. In htab_map_alloc(), we already have htab->elem_size = sizeof(struct htab_elem) + round_up(htab->map.key_size, 8); if (percpu) htab->elem_size += sizeof(void *); else htab->elem_size += round_up(htab->map.value_size, 8); So storing pptr with 8-byte alignment won't cause any problem and can fix kmemleak too. The issue can be reproduced with bpf selftest as well: 1. Enable CONFIG_DEBUG_KMEMLEAK config 2. Add a getchar() before skel destroy in test_hash_map() in prog_tests/for_each.c. The purpose is to keep map available so kmemleak can be detected. 3. run './test_progs -t for_each/hash_map &' and a kmemleak should be reported. Reported-by: Vlad Poenaru Signed-off-by: Yonghong Song Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20250224175514.2207227-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/hashtab.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 3ec941a0ea41c..bb3ba8ebaf3d2 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -198,12 +198,12 @@ static bool htab_is_percpu(const struct bpf_htab *htab) static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size, void __percpu *pptr) { - *(void __percpu **)(l->key + key_size) = pptr; + *(void __percpu **)(l->key + roundup(key_size, 8)) = pptr; } static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size) { - return *(void __percpu **)(l->key + key_size); + return *(void __percpu **)(l->key + roundup(key_size, 8)); } static void *fd_htab_map_get_ptr(const struct bpf_map *map, struct htab_elem *l) @@ -2355,7 +2355,7 @@ static int htab_percpu_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn *insn++ = BPF_EMIT_CALL(__htab_map_lookup_elem); *insn++ = BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3); *insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, - offsetof(struct htab_elem, key) + map->key_size); + offsetof(struct htab_elem, key) + roundup(map->key_size, 8)); *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0); *insn++ = BPF_MOV64_PERCPU_REG(BPF_REG_0, BPF_REG_0); -- 2.39.5