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 AD629178CF8; Fri, 4 Apr 2025 00:04:23 +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=1743725063; cv=none; b=ZKGPnJa22pJwL5WA78sjGjoXkWQN5Lc17TGjALWANRgsAoO7L7Mab69lUXu2mkRqDCwv79pWDWVVDf+moHN+UTNZALTcMeZT3yLmMHiFNtoBYIfgAMCc+z9295qKsYokn6jbEJhUMsFsuMu/A5qWBuOETobEFYN8DaiPG6uYPOE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743725063; c=relaxed/simple; bh=Vs7ETizBunCJX9rKsc3qwP8DPfDySkX/BY3oWLYBDu0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=dC+GOv2+5X84tTno62uAlRP/qeA2Adza7MhwAEztXNAVrfEeqBqvhFdqTXd/0IlOY/OdLudyl5+Tqu/v6DSedZQE1mw43rooBcYTZPWcZCfuR50W84PFTmqoVJ5e6/S3DO145rmHCA5zGYa/7yiPQoCWfKGoF0/DE3MExlYvuEw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kdQARpbJ; 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="kdQARpbJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09145C4CEE9; Fri, 4 Apr 2025 00:04:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743725063; bh=Vs7ETizBunCJX9rKsc3qwP8DPfDySkX/BY3oWLYBDu0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kdQARpbJpH8KE8p7ZBTqMRGn4vzmhsTpAGOEOaQdHHnwQG6DB9bui9UPF8rxCUmAO D8aav3hpLP+ExBMqwC2i+DCckIkBMEW3ic/sCwPRSSLfCMPZ141U95/HvMiFIMQ4Rc MDL2W/vKsEN4EoQ1vbK6SxOTA/Lqgj7lFIoHRZZWfSO5ZyJPc7OwkqPMqjbk8iUclY tRrpV3+fW2kwPwwAVKj7amPI+VpLrU9UowVjJd7PpwrUh7eRxk2aZrHRY67nGedjT6 G2A1nbk6e8HBA/853okaSuheVUm83kceaW1ZM83RDNr8bTAlJY+LOFZqTulG9rIr8E 1gVs4GaxHhEgQ== 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 6.14 09/23] bpf: Fix kmemleak warning for percpu hashmap Date: Thu, 3 Apr 2025 20:03:46 -0400 Message-Id: <20250404000402.2688049-9-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250404000402.2688049-1-sashal@kernel.org> References: <20250404000402.2688049-1-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 6.14 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 4a9eeb7aef855..c308300fc72f6 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) @@ -2354,7 +2354,7 @@ 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