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 3E7643921FB; Sat, 17 Oct 2026 17:25:50 +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=1792257951; cv=none; b=gFoPUNAw2hs519fboo/BUVrMo6zUy4xYTxHO1FXIZIKMtl2PWkKGK2RTfbXtnZG/pLc0ukzNvvjreKzRQy0HXJNoYrFrBiEjc1nd+zvPTuE0tY/mPEhD4eDUfAk7OXqgSwnRKaxD5rU+BBRxMhAlV5PV7v0ZCzyyX48Ns+Ivqeg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792257951; c=relaxed/simple; bh=Noliw5YuXhJC+oWqNWx5mW+BU9VId98MDKpDkpuGhUE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=E5PWBVx68FYRNFm3ew7xfsYpqVpGsszHPVnLQpv0cvyuU0DklerZ1cMmeFdK5kZfdLfGImI57VaMj0KjyC7thktvN7Mo6OXmPR/raEjCrhYRfHn5RK3/cUQsQH9SFFytblVlv1rSQQxnu8BbRUXenaAcud3pTesV9MVYq4pHdVs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=He8B2Tdm; 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="He8B2Tdm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8856B1F000C4; Sat, 17 Oct 2026 17:25:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792257950; bh=4B0FR2AnJTpCX3M4izdAcxOsgug8ZScNlo2+Il9j0rE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=He8B2TdmKtyBEfHS/tt1ji4G+jjXXd/NjpMdGCEt9mcSqAF/jKU4kKGizLwOne/5r zdF/wV9QvdFkGfACF+3YhXKsKUwA26DNJzFXRYuH1/+pNeQ4XW9nHfGQ8siekjq1z9 VxJ1ElePXSyYgSjbL4VphtoB6clFZdvYRzHRnprc= 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 6.6 0723/1674] bpf: Fix kmemleak warning for percpu hashmap Date: Sat, 17 Oct 2026 17:49:55 +0200 Message-ID: <20261017160449.667727424@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160431.119607952@linuxfoundation.org> References: <20261017160431.119607952@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-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 | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index e14a0caa07bfa..fb7f64c494b0e 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -197,12 +197,12 @@ 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) -- 2.53.0