From: "tip-bot2 for Andy Lutomirski" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
x86 <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: [tip: x86/urgent] x86/entry, selftests: Further improve user entry sanity checks
Date: Sat, 04 Jul 2020 17:49:10 -0000 [thread overview]
Message-ID: <159388495037.4006.7851835406474127743.tip-bot2@tip-bot2> (raw)
In-Reply-To: <881de09e786ab93ce56ee4a2437ba2c308afe7a9.1593795633.git.luto@kernel.org>
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 3c73b81a9164d0c1b6379d6672d2772a9e95168e
Gitweb: https://git.kernel.org/tip/3c73b81a9164d0c1b6379d6672d2772a9e95168e
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Fri, 03 Jul 2020 10:02:54 -07:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 04 Jul 2020 19:47:25 +02:00
x86/entry, selftests: Further improve user entry sanity checks
Chasing down a Xen bug caused me to realize that the new entry sanity
checks are still fairly weak. Add some more checks.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/881de09e786ab93ce56ee4a2437ba2c308afe7a9.1593795633.git.luto@kernel.org
---
arch/x86/entry/common.c | 19 +++++++++++++++++++
tools/testing/selftests/x86/syscall_nt.c | 11 +++++++++++
2 files changed, 30 insertions(+)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index f392a8b..e83b3f1 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -49,6 +49,23 @@
static void check_user_regs(struct pt_regs *regs)
{
if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
+ /*
+ * Make sure that the entry code gave us a sensible EFLAGS
+ * register. Native because we want to check the actual CPU
+ * state, not the interrupt state as imagined by Xen.
+ */
+ unsigned long flags = native_save_fl();
+ WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF |
+ X86_EFLAGS_NT));
+
+ /* We think we came from user mode. Make sure pt_regs agrees. */
+ WARN_ON_ONCE(!user_mode(regs));
+
+ /*
+ * All entries from user mode (except #DF) should be on the
+ * normal thread stack and should have user pt_regs in the
+ * correct location.
+ */
WARN_ON_ONCE(!on_thread_stack());
WARN_ON_ONCE(regs != task_pt_regs(current));
}
@@ -577,6 +594,7 @@ SYSCALL_DEFINE0(ni_syscall)
bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
{
if (user_mode(regs)) {
+ check_user_regs(regs);
enter_from_user_mode();
return false;
}
@@ -710,6 +728,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
*/
void noinstr idtentry_enter_user(struct pt_regs *regs)
{
+ check_user_regs(regs);
enter_from_user_mode();
}
diff --git a/tools/testing/selftests/x86/syscall_nt.c b/tools/testing/selftests/x86/syscall_nt.c
index 970e5e1..a108b80 100644
--- a/tools/testing/selftests/x86/syscall_nt.c
+++ b/tools/testing/selftests/x86/syscall_nt.c
@@ -81,5 +81,16 @@ int main(void)
printf("[RUN]\tSet NT|AC|TF and issue a syscall\n");
do_it(X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_TF);
+ /*
+ * Now try DF. This is evil and it's plausible that we will crash
+ * glibc, but glibc would have to do something rather surprising
+ * for this to happen.
+ */
+ printf("[RUN]\tSet DF and issue a syscall\n");
+ do_it(X86_EFLAGS_DF);
+
+ printf("[RUN]\tSet TF|DF and issue a syscall\n");
+ do_it(X86_EFLAGS_TF | X86_EFLAGS_DF);
+
return nerrs == 0 ? 0 : 1;
}
next prev parent reply other threads:[~2020-07-04 17:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-03 17:02 [PATCH entry v2 0/6] x86/entry: Fixes and cleanups Andy Lutomirski
2020-07-03 17:02 ` [PATCH entry v2 1/6] x86/entry/compat: Clear RAX high bits on Xen PV SYSENTER Andy Lutomirski
2020-07-04 17:49 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-07-03 17:02 ` [PATCH entry v2 2/6] x86/entry, selftests: Further improve user entry sanity checks Andy Lutomirski
2020-07-04 17:49 ` tip-bot2 for Andy Lutomirski [this message]
2020-08-20 10:23 ` [tip: x86/urgent] " peterz
2020-08-22 21:59 ` Andy Lutomirski
2020-07-03 17:02 ` [PATCH entry v2 3/6] x86/entry/xen: Route #DB correctly on Xen PV Andy Lutomirski
2020-07-04 17:49 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-07-06 8:41 ` [PATCH entry v2 3/6] " Michal Kubecek
2020-07-06 8:57 ` Jürgen Groß
2020-07-06 9:32 ` Michal Kubecek
2020-07-03 17:02 ` [PATCH entry v2 4/6] x86/entry/32: Fix #MC and #DB wiring on x86_32 Andy Lutomirski
2020-07-04 17:49 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-07-03 17:02 ` [PATCH entry v2 5/6] x86/ldt: Disable 16-bit segments on Xen PV Andy Lutomirski
2020-07-03 19:00 ` Andrew Cooper
2020-07-04 17:49 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-07-03 17:02 ` [PATCH entry v2 6/6] x86/entry: Rename idtentry_enter/exit_cond_rcu() to idtentry_enter/exit() Andy Lutomirski
2020-07-07 8:23 ` [tip: x86/entry] " tip-bot2 for Andy Lutomirski
2020-07-03 17:31 ` [PATCH entry v2 0/6] x86/entry: Fixes and cleanups Peter Zijlstra
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