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 71E4D1F8739; Fri, 4 Apr 2025 00:06:00 +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=1743725160; cv=none; b=Joc99+eQq3fUHMZaHx9Qj2yEilDxdnBCvRuzz7cuZsOKH435kdcc4Sproj+okgHa8GFGf0iQzCHS5IxnB+advMjqyJTa4NaNaFtQ/JiyR+4V8dev1TAj+i45cDTsb5+WULU/Yc2tm0A1P95psWkLqVXritw3iYEz/jMZghwzwwQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743725160; c=relaxed/simple; bh=lbJeD+K4S5kfWbH0kRQUiptWwBbMhU0X5XWz0+4Wh/U=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=n/1ktFY1bVbiL3KT4zZSVuhWHE7/GSe0vZzjP6NdWLu2cdTyu02tuSsTfRhuHovBp2ZwjaQAe6uyusH7QDSmJYhxpF0LkA9eHr/2k/jO0K3lIRi60PFqB+oBb6+apJ0VUtbqE1tSlVoJTF12zVQagObBT6yzM85n04z3ZZmzqc0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QXAh+R9S; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QXAh+R9S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D90A0C4CEE5; Fri, 4 Apr 2025 00:05:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743725160; bh=lbJeD+K4S5kfWbH0kRQUiptWwBbMhU0X5XWz0+4Wh/U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QXAh+R9S4XvbDr67bLZHl4wdPCVNAvk16s4fftN89AQvPB5rJ9WddqxT3Joic3QTe ssglyHO8aKPPnZupDQmQ3rPKJCY5axKKtiyqlEq4lYITybfIssY9orlNauuVYJWkHW JUP4zugGbEoGDJKbmh8bcu1+ZpbGjfFPmJRSr/WZuz3Ly2m3CE52S2EFP5F0suIVP5 q2f7K0aBhaOvGwEB4BRiCfnMPiNsYFc0O2kJoIli68ZbbjZa+ebtqop2nTURiIECqC 7yz5WGgk7WauG/7E8fZa1y/gMJAmN42Rdsl/CvvFl6VZBe+fsAUSF5WkaX8sgwjgSJ V7ckInlg8iwoA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Yonghong Song , Vlad Poenaru , Martin KaFai Lau , Alexei Starovoitov , Sasha Levin , daniel@iogearbox.net, andrii@kernel.org, bpf@vger.kernel.org Subject: [PATCH AUTOSEL 6.12 08/20] bpf: Fix kmemleak warning for percpu hashmap Date: Thu, 3 Apr 2025 20:05:28 -0400 Message-Id: <20250404000541.2688670-8-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250404000541.2688670-1-sashal@kernel.org> References: <20250404000541.2688670-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.12.21 Content-Transfer-Encoding: 8bit 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