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 35A991D68D for ; Wed, 4 Oct 2023 18:16:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="APLXGkb1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACA7BC433C9; Wed, 4 Oct 2023 18:16:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1696443404; bh=h8cxgEOexgFsNKv4LlsYPtR19gUViUPbl8BBNL4jUeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=APLXGkb1g5cqz76WDfXliVz5uocGGaaAl+vv68T87LrfDKu3/Y0p8q4DsMQ0UZaOb Ca/aDEKmyu5SM+V2LSERnhchmImhtR2X06X19IGIOJg/+S5kOro9qVN8VPeXHj4X9E Jf3E4kDI3p3k5myyu+pAD1dcQSi45jQCAwC9Omuw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+97522333291430dd277f@syzkaller.appspotmail.com, Marco Elver , Daniel Borkmann , Sasha Levin Subject: [PATCH 6.1 144/259] bpf: Annotate bpf_long_memcpy with data_race Date: Wed, 4 Oct 2023 19:55:17 +0200 Message-ID: <20231004175223.911928435@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231004175217.404851126@linuxfoundation.org> References: <20231004175217.404851126@linuxfoundation.org> User-Agent: quilt/0.67 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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Borkmann [ Upstream commit 6a86b5b5cd76d2734304a0173f5f01aa8aa2025e ] syzbot reported a data race splat between two processes trying to update the same BPF map value via syscall on different CPUs: BUG: KCSAN: data-race in bpf_percpu_array_update / bpf_percpu_array_update write to 0xffffe8fffe7425d8 of 8 bytes by task 8257 on cpu 1: bpf_long_memcpy include/linux/bpf.h:428 [inline] bpf_obj_memcpy include/linux/bpf.h:441 [inline] copy_map_value_long include/linux/bpf.h:464 [inline] bpf_percpu_array_update+0x3bb/0x500 kernel/bpf/arraymap.c:380 bpf_map_update_value+0x190/0x370 kernel/bpf/syscall.c:175 generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1749 bpf_map_do_batch+0x2df/0x3d0 kernel/bpf/syscall.c:4648 __sys_bpf+0x28a/0x780 __do_sys_bpf kernel/bpf/syscall.c:5241 [inline] __se_sys_bpf kernel/bpf/syscall.c:5239 [inline] __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5239 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd write to 0xffffe8fffe7425d8 of 8 bytes by task 8268 on cpu 0: bpf_long_memcpy include/linux/bpf.h:428 [inline] bpf_obj_memcpy include/linux/bpf.h:441 [inline] copy_map_value_long include/linux/bpf.h:464 [inline] bpf_percpu_array_update+0x3bb/0x500 kernel/bpf/arraymap.c:380 bpf_map_update_value+0x190/0x370 kernel/bpf/syscall.c:175 generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1749 bpf_map_do_batch+0x2df/0x3d0 kernel/bpf/syscall.c:4648 __sys_bpf+0x28a/0x780 __do_sys_bpf kernel/bpf/syscall.c:5241 [inline] __se_sys_bpf kernel/bpf/syscall.c:5239 [inline] __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5239 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd value changed: 0x0000000000000000 -> 0xfffffff000002788 The bpf_long_memcpy is used with 8-byte aligned pointers, power-of-8 size and forced to use long read/writes to try to atomically copy long counters. It is best-effort only and no barriers are here since it _will_ race with concurrent updates from BPF programs. The bpf_long_memcpy() is called from bpf(2) syscall. Marco suggested that the best way to make this known to KCSAN would be to use data_race() annotation. Reported-by: syzbot+97522333291430dd277f@syzkaller.appspotmail.com Suggested-by: Marco Elver Signed-off-by: Daniel Borkmann Acked-by: Marco Elver Link: https://lore.kernel.org/bpf/000000000000d87a7f06040c970c@google.com Link: https://lore.kernel.org/bpf/57628f7a15e20d502247c3b55fceb1cb2b31f266.1693342186.git.daniel@iogearbox.net Signed-off-by: Sasha Levin --- include/linux/bpf.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index b3d3aa8437dce..1ed2ec035e779 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -301,7 +301,7 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size) size /= sizeof(long); while (size--) - *ldst++ = *lsrc++; + data_race(*ldst++ = *lsrc++); } /* copy everything but bpf_spin_lock, bpf_timer, and kptrs. There could be one of each. */ -- 2.40.1