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 97B1F1171A for ; Mon, 21 Aug 2023 20:08:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 18BD3C43395; Mon, 21 Aug 2023 20:08:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692648500; bh=beFuRUs66v2wXy+j9FqyEF57gIoFuQr1pWKalieRImY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qwO18vUxl2Ba3j6xlUIFaT5g8xC9ilmbaod7KL7xcSo1cG8Rydlhmuiw/cXT04JNL 2m0qeR+0tQ2hCp2EEnUVtAnYHcGCOrCa3y8ejjN1Y0+i5HaGB48PM2Jhd6e8C2n/W6 OCZb1kaxJKichNarbzsKx16LTtF7MF2XrtmXz2Dk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Felix Yan , Ruizhe Pan , Shiqi Zhang , Celeste Liu , Emil Renner Berthing , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Guo Ren , Palmer Dabbelt , Sasha Levin Subject: [PATCH 6.4 198/234] riscv: entry: set a0 = -ENOSYS only when syscall != -1 Date: Mon, 21 Aug 2023 21:42:41 +0200 Message-ID: <20230821194137.578534960@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230821194128.754601642@linuxfoundation.org> References: <20230821194128.754601642@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Celeste Liu [ Upstream commit 52449c17bdd1540940e21511612b58acebc49c06 ] When we test seccomp with 6.4 kernel, we found errno has wrong value. If we deny NETLINK_AUDIT with EAFNOSUPPORT, after f0bddf50586d, we will get ENOSYS instead. We got same result with commit 9c2598d43510 ("riscv: entry: Save a0 prior syscall_enter_from_user_mode()"). After analysing code, we think that regs->a0 = -ENOSYS should only be executed when syscall != -1. In __seccomp_filter, when seccomp rejected this syscall with specified errno, they will set a0 to return number as syscall ABI, and then return -1. This return number is finally pass as return number of syscall_enter_from_user_mode, and then is compared with NR_syscalls after converted to ulong (so it will be ULONG_MAX). The condition syscall < NR_syscalls will always be false, so regs->a0 = -ENOSYS is always executed. It covered a0 set by seccomp, so we always get ENOSYS when match seccomp RET_ERRNO rule. Fixes: f0bddf50586d ("riscv: entry: Convert to generic entry") Reported-by: Felix Yan Co-developed-by: Ruizhe Pan Signed-off-by: Ruizhe Pan Co-developed-by: Shiqi Zhang Signed-off-by: Shiqi Zhang Signed-off-by: Celeste Liu Tested-by: Felix Yan Tested-by: Emil Renner Berthing Reviewed-by: Björn Töpel Reviewed-by: Guo Ren Link: https://lore.kernel.org/r/20230801141607.435192-1-CoelacanthusHex@gmail.com Signed-off-by: Palmer Dabbelt Signed-off-by: Sasha Levin --- arch/riscv/kernel/traps.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 8c258b78c925c..bd19e885dcec1 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -268,16 +268,16 @@ asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs) asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs) { if (user_mode(regs)) { - ulong syscall = regs->a7; + long syscall = regs->a7; regs->epc += 4; regs->orig_a0 = regs->a0; syscall = syscall_enter_from_user_mode(regs, syscall); - if (syscall < NR_syscalls) + if (syscall >= 0 && syscall < NR_syscalls) syscall_handler(regs, syscall); - else + else if (syscall != -1) regs->a0 = -ENOSYS; syscall_exit_to_user_mode(regs); -- 2.40.1