From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZrAWuGfSYeCrbclOG9gOya45wwqNr/C00WPxjDaKaorl416wv36T1h6mpbIR+RU74VEgsco ARC-Seal: i=1; a=rsa-sha256; t=1526937472; cv=none; d=google.com; s=arc-20160816; b=b2QHJYJnU+rgf1iShMeDCrnh/Q2XgI9M5y75EyBKjYZsCZQYUAAJ8UQp/e907UePnB RxDl7IzL8cIQ7WG+fYCZLixGPRXp/rgodLuFsZ9xoI/nbSEO1feHSYRlD7H8VBDLAGC4 GCxoUOlbI0dNeWykWVooNEbZKiIRVy4cRFx6rghGqk5ob5jfIDkT3EH+BT59XSitdDn7 XXgqlFW203M3NEp8N3WmFKFF3KYYN6AgvUAewei2ZHtoSIPNx+U48Qo4ynggdaHoTdHR bpZiqSSo9pUW85/20o05CMTiyYEw+b0fNrfa7gME3axWFsLguHyKo8lAFexFwsQQUYmJ rHjw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=yIw/I0jh8KF5PYidftSVZJmva1ZrgTZPRO0dfbO79lc=; b=Wc4fqABlO/aN7jVvKJAFUkkgkpf0wbeouOcvi7/A1UiiK4gr/vK3rbvkRc90Drgix0 3ZqrjqC77DxmzJUWUOVYNKQS+M5klj9w/h16CZJJMgX+h0/9vAfF/DeMMz07lZyvYGHG KKP4z7SbQ2w90Y+KhsEycD0OsLpcm2ZCtWSgjwmQ3zJw/FeCdtcwiC2/QmagK0OhJjgm xRWtHuyyPPySMb/JUad6yB3/RH93wUYCjRqxtdZspuabFh3A5irwwjI6M15UWWV1xUUB XXRv2oeZ8WhEeSYg+zTtUnyPECOcXUuVapeKVvQ4aVYaAvthEMx1Z5+yFiujE+ouMigq +spA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=wiyP0FYc; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=wiyP0FYc; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kees Cook , Thomas Gleixner , David Woodhouse Subject: [PATCH 4.9 61/87] seccomp: Add filter flag to opt-out of SSB mitigation Date: Mon, 21 May 2018 23:11:37 +0200 Message-Id: <20180521210425.604678841@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180521210420.222671977@linuxfoundation.org> References: <20180521210420.222671977@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1601109987144420611?= X-GMAIL-MSGID: =?utf-8?q?1601109987144420611?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook commit 00a02d0c502a06d15e07b857f8ff921e3e402675 upstream If a seccomp user is not interested in Speculative Store Bypass mitigation by default, it can set the new SECCOMP_FILTER_FLAG_SPEC_ALLOW flag when adding filters. Signed-off-by: Kees Cook Signed-off-by: Thomas Gleixner Signed-off-by: David Woodhouse Signed-off-by: Greg Kroah-Hartman --- include/linux/seccomp.h | 3 - include/uapi/linux/seccomp.h | 4 + kernel/seccomp.c | 19 +++--- tools/testing/selftests/seccomp/seccomp_bpf.c | 78 +++++++++++++++++++++++++- 4 files changed, 93 insertions(+), 11 deletions(-) --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -3,7 +3,8 @@ #include -#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC) +#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC | \ + SECCOMP_FILTER_FLAG_SPEC_ALLOW) #ifdef CONFIG_SECCOMP --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -15,7 +15,9 @@ #define SECCOMP_SET_MODE_FILTER 1 /* Valid flags for SECCOMP_SET_MODE_FILTER */ -#define SECCOMP_FILTER_FLAG_TSYNC 1 +#define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0) +/* In v4.14+ SECCOMP_FILTER_FLAG_LOG is (1UL << 1) */ +#define SECCOMP_FILTER_FLAG_SPEC_ALLOW (1UL << 2) /* * All BPF programs must return a 32-bit value. --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -230,7 +230,8 @@ static inline void spec_mitigate(struct } static inline void seccomp_assign_mode(struct task_struct *task, - unsigned long seccomp_mode) + unsigned long seccomp_mode, + unsigned long flags) { assert_spin_locked(&task->sighand->siglock); @@ -240,8 +241,9 @@ static inline void seccomp_assign_mode(s * filter) is set. */ smp_mb__before_atomic(); - /* Assume seccomp processes want speculation flaw mitigation. */ - spec_mitigate(task, PR_SPEC_STORE_BYPASS); + /* Assume default seccomp processes want spec flaw mitigation. */ + if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0) + spec_mitigate(task, PR_SPEC_STORE_BYPASS); set_tsk_thread_flag(task, TIF_SECCOMP); } @@ -309,7 +311,7 @@ static inline pid_t seccomp_can_sync_thr * without dropping the locks. * */ -static inline void seccomp_sync_threads(void) +static inline void seccomp_sync_threads(unsigned long flags) { struct task_struct *thread, *caller; @@ -350,7 +352,8 @@ static inline void seccomp_sync_threads( * allow one thread to transition the other. */ if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) - seccomp_assign_mode(thread, SECCOMP_MODE_FILTER); + seccomp_assign_mode(thread, SECCOMP_MODE_FILTER, + flags); } } @@ -469,7 +472,7 @@ static long seccomp_attach_filter(unsign /* Now that the new filter is in place, synchronize to all threads. */ if (flags & SECCOMP_FILTER_FLAG_TSYNC) - seccomp_sync_threads(); + seccomp_sync_threads(flags); return 0; } @@ -729,7 +732,7 @@ static long seccomp_set_mode_strict(void #ifdef TIF_NOTSC disable_TSC(); #endif - seccomp_assign_mode(current, seccomp_mode); + seccomp_assign_mode(current, seccomp_mode, 0); ret = 0; out: @@ -787,7 +790,7 @@ static long seccomp_set_mode_filter(unsi /* Do not free the successfully attached filter. */ prepared = NULL; - seccomp_assign_mode(current, seccomp_mode); + seccomp_assign_mode(current, seccomp_mode, flags); out: spin_unlock_irq(¤t->sighand->siglock); if (flags & SECCOMP_FILTER_FLAG_TSYNC) --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1692,7 +1692,11 @@ TEST_F_SIGNAL(TRACE_syscall, kill_after_ #endif #ifndef SECCOMP_FILTER_FLAG_TSYNC -#define SECCOMP_FILTER_FLAG_TSYNC 1 +#define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0) +#endif + +#ifndef SECCOMP_FILTER_FLAG_SPEC_ALLOW +#define SECCOMP_FILTER_FLAG_SPEC_ALLOW (1UL << 2) #endif #ifndef seccomp @@ -1791,6 +1795,78 @@ TEST(seccomp_syscall_mode_lock) } } +/* + * Test detection of known and unknown filter flags. Userspace needs to be able + * to check if a filter flag is supported by the current kernel and a good way + * of doing that is by attempting to enter filter mode, with the flag bit in + * question set, and a NULL pointer for the _args_ parameter. EFAULT indicates + * that the flag is valid and EINVAL indicates that the flag is invalid. + */ +TEST(detect_seccomp_filter_flags) +{ + unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC, + SECCOMP_FILTER_FLAG_SPEC_ALLOW }; + unsigned int flag, all_flags; + int i; + long ret; + + /* Test detection of known-good filter flags */ + for (i = 0, all_flags = 0; i < ARRAY_SIZE(flags); i++) { + int bits = 0; + + flag = flags[i]; + /* Make sure the flag is a single bit! */ + while (flag) { + if (flag & 0x1) + bits ++; + flag >>= 1; + } + ASSERT_EQ(1, bits); + flag = flags[i]; + + ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL); + ASSERT_NE(ENOSYS, errno) { + TH_LOG("Kernel does not support seccomp syscall!"); + } + EXPECT_EQ(-1, ret); + EXPECT_EQ(EFAULT, errno) { + TH_LOG("Failed to detect that a known-good filter flag (0x%X) is supported!", + flag); + } + + all_flags |= flag; + } + + /* Test detection of all known-good filter flags */ + ret = seccomp(SECCOMP_SET_MODE_FILTER, all_flags, NULL); + EXPECT_EQ(-1, ret); + EXPECT_EQ(EFAULT, errno) { + TH_LOG("Failed to detect that all known-good filter flags (0x%X) are supported!", + all_flags); + } + + /* Test detection of an unknown filter flag */ + flag = -1; + ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL); + EXPECT_EQ(-1, ret); + EXPECT_EQ(EINVAL, errno) { + TH_LOG("Failed to detect that an unknown filter flag (0x%X) is unsupported!", + flag); + } + + /* + * Test detection of an unknown filter flag that may simply need to be + * added to this test + */ + flag = flags[ARRAY_SIZE(flags) - 1] << 1; + ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL); + EXPECT_EQ(-1, ret); + EXPECT_EQ(EINVAL, errno) { + TH_LOG("Failed to detect that an unknown filter flag (0x%X) is unsupported! Does a new flag need to be added to this test?", + flag); + } +} + TEST(TSYNC_first) { struct sock_filter filter[] = {