Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755347Ab3COWAV (ORCPT ); Fri, 15 Mar 2013 18:00:21 -0400 Received: from terminus.zytor.com ([198.137.202.10]:38277 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754093Ab3COWAU (ORCPT ); Fri, 15 Mar 2013 18:00:20 -0400 Message-ID: <5143990B.9000007@zytor.com> Date: Fri, 15 Mar 2013 14:56:27 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Paul Moore CC: x86@kernel.org, keescook@chromium.org, linux-kernel@vger.kernel.org, coreyb@linux.vnet.ibm.com, wad@chromium.org, "H.J. Lu" Subject: Re: [PATCH] x86: remove the x32 syscall bitmask from syscall_get_nr() References: <20130215172143.12549.10292.stgit@localhost> <2012624.RMfkAO316Z@sifl> <1674827.FAh5HIjCC0@sifl> In-Reply-To: <1674827.FAh5HIjCC0@sifl> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3511 Lines: 85 On 03/15/2013 02:15 PM, Paul Moore wrote: > On Tuesday, February 26, 2013 03:58:23 PM Paul Moore wrote: >> On Friday, February 15, 2013 12:21:43 PM Paul Moore wrote: >>> Commit fca460f95e928bae373daa8295877b6905bc62b8 simplified the x32 >>> implementation by creating a syscall bitmask, equal to 0x40000000, that >>> could be applied to x32 syscalls such that the masked syscall number >>> would be the same as a x86_64 syscall. While that patch was a nice >>> way to simplify the code, it went a bit too far by adding the mask to >>> syscall_get_nr(); returning the masked syscall numbers can cause >>> confusion with callers that expect syscall numbers matching the x32 >>> ABI, e.g. unmasked syscall numbers. >>> >>> This patch fixes this by simply removing the mask from syscall_get_nr() >>> while preserving the other changes from the original commit. While >>> there are several syscall_get_nr() callers in the kernel, most simply >>> check that the syscall number is greater than zero, in this case this >>> patch will have no effect. Of those remaining callers, they appear >>> to be few, seccomp and ftrace, and from my testing of seccomp without >>> this patch the original commit definitely breaks things; the seccomp >>> filter does not correctly filter the syscalls due to the difference in >>> syscall numbers in the BPF filter and the value from syscall_get_nr(). >>> Applying this patch restores the seccomp BPF filter functionality on >>> x32. >>> >>> I've tested this patch with the seccomp BPF filters as well as ftrace >>> and everything looks reasonable to me; needless to say general usage >>> seemed fine as well. >> >> I just wanted to check and see where things stood with this patch. I'm not >> overly concerned about how this problem is solved, just that it is solved. >> If someone else has a better approach that is fine with me; I'll even make >> the offer to do additional testing if needed. > > Anyone? The seccomp filter bits are completely broken on x32 and I'd like to > get this fixed, if not with this patch then something else - I'm more than > happy to test/verify/etc whatever solution is deemed best ... > Seems good to me -- H.J., do you seen any problem with this? -hpa >>> Signed-off-by: Paul Moore >>> Cc: stable@vger.kernel.org >>> Cc: Will Drewry >>> Cc: H. Peter Anvin >>> --- >>> >>> arch/x86/include/asm/syscall.h | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/syscall.h >>> b/arch/x86/include/asm/syscall.h index 1ace47b..2e188d6 100644 >>> --- a/arch/x86/include/asm/syscall.h >>> +++ b/arch/x86/include/asm/syscall.h >>> @@ -29,13 +29,13 @@ extern const unsigned long sys_call_table[]; >>> >>> */ >>> >>> static inline int syscall_get_nr(struct task_struct *task, struct pt_regs >>> >>> *regs) { >>> - return regs->orig_ax & __SYSCALL_MASK; >>> + return regs->orig_ax; >>> >>> } >>> >>> static inline void syscall_rollback(struct task_struct *task, >>> >>> struct pt_regs *regs) >>> >>> { >>> >>> - regs->ax = regs->orig_ax & __SYSCALL_MASK; >>> + regs->ax = regs->orig_ax; >>> >>> } >>> >>> static inline long syscall_get_error(struct task_struct *task, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/