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From: Tony Luck <tony.luck@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Jue Wang <juew@google.com>, Ding Hui <dinghui@sangfor.com.cn>,
	naoya.horiguchi@nec.com, osalvador@suse.de,
	Youquan Song <youquan.song@intel.com>,
	huangcun@sangfor.com.cn, x86@kernel.org,
	linux-edac@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Tony Luck <tony.luck@intel.com>
Subject: [PATCH v2 2/3] x86/mce: Change to not send SIGBUS error during copy from user
Date: Tue, 17 Aug 2021 17:29:41 -0700	[thread overview]
Message-ID: <20210818002942.1607544-3-tony.luck@intel.com> (raw)
In-Reply-To: <20210818002942.1607544-1-tony.luck@intel.com>

Sending a SIGBUS for a copy from user is not the correct semantic.
System calls should return -EFAULT (or a short count for write(2)).

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/cpu/mce/core.c | 35 +++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 94830ee9581c..957ec60cd2a8 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1269,7 +1269,7 @@ static void kill_me_maybe(struct callback_head *cb)
 		flags |= MF_MUST_KILL;
 
 	ret = memory_failure(p->mce_addr >> PAGE_SHIFT, flags);
-	if (!ret && !(p->mce_kflags & MCE_IN_KERNEL_COPYIN)) {
+	if (!ret) {
 		set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
 		sync_core();
 		return;
@@ -1283,15 +1283,21 @@ static void kill_me_maybe(struct callback_head *cb)
 	if (ret == -EHWPOISON)
 		return;
 
-	if (p->mce_vaddr != (void __user *)-1l) {
-		force_sig_mceerr(BUS_MCEERR_AR, p->mce_vaddr, PAGE_SHIFT);
-	} else {
-		pr_err("Memory error not recovered");
-		kill_me_now(cb);
-	}
+	pr_err("Memory error not recovered");
+	kill_me_now(cb);
+}
+
+static void kill_me_never(struct callback_head *cb)
+{
+	struct task_struct *p = container_of(cb, struct task_struct, mce_kill_me);
+
+	p->mce_count = 0;
+	pr_err("Kernel accessed poison in user space at %llx\n", p->mce_addr);
+	if (!memory_failure(p->mce_addr >> PAGE_SHIFT, 0))
+		set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
 }
 
-static void queue_task_work(struct mce *m, char *msg, int kill_current_task)
+static void queue_task_work(struct mce *m, char *msg, void (*func)(struct callback_head *))
 {
 	int count = ++current->mce_count;
 
@@ -1301,11 +1307,7 @@ static void queue_task_work(struct mce *m, char *msg, int kill_current_task)
 		current->mce_kflags = m->kflags;
 		current->mce_ripv = !!(m->mcgstatus & MCG_STATUS_RIPV);
 		current->mce_whole_page = whole_page(m);
-
-		if (kill_current_task)
-			current->mce_kill_me.func = kill_me_now;
-		else
-			current->mce_kill_me.func = kill_me_maybe;
+		current->mce_kill_me.func = func;
 	}
 
 	/* Ten is likley overkill. Don't expect more than two faults before task_work() */
@@ -1456,7 +1458,10 @@ noinstr void do_machine_check(struct pt_regs *regs)
 		/* If this triggers there is no way to recover. Die hard. */
 		BUG_ON(!on_thread_stack() || !user_mode(regs));
 
-		queue_task_work(&m, msg, kill_current_task);
+		if (kill_current_task)
+			queue_task_work(&m, msg, kill_me_now);
+		else
+			queue_task_work(&m, msg, kill_me_maybe);
 
 	} else {
 		/*
@@ -1474,7 +1479,7 @@ noinstr void do_machine_check(struct pt_regs *regs)
 		}
 
 		if (m.kflags & MCE_IN_KERNEL_COPYIN)
-			queue_task_work(&m, msg, kill_current_task);
+			queue_task_work(&m, msg, kill_me_never);
 	}
 out:
 	mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
-- 
2.29.2


  parent reply	other threads:[~2021-08-18  0:30 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-06 19:06 [PATCH 0/3] More machine check recovery fixes Tony Luck
2021-07-06 19:06 ` [PATCH 1/3] x86/mce: Change to not send SIGBUS error during copy from user Tony Luck
2021-07-06 19:06 ` [PATCH 2/3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-07-06 19:06 ` [PATCH 3/3] x86/mce: Drop copyin special case for #MC Tony Luck
2021-08-18  0:29 ` [PATCH v2 0/3] More machine check recovery fixes Tony Luck
2021-08-18  0:29   ` [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-08-20 17:31     ` Borislav Petkov
2021-08-20 18:59       ` Luck, Tony
2021-08-20 19:27         ` Borislav Petkov
2021-08-20 20:23           ` Luck, Tony
2021-08-21  4:51             ` Tony Luck
2021-08-21 21:51               ` Al Viro
2021-08-22 14:36             ` Borislav Petkov
2021-08-20 20:33           ` Luck, Tony
2021-08-22 14:46             ` Borislav Petkov
2021-08-23 15:24               ` Luck, Tony
2021-09-13  9:24     ` Borislav Petkov
2021-09-13 21:52       ` [PATCH v3] " Luck, Tony
2021-09-14  8:28         ` Borislav Petkov
2021-08-18  0:29   ` Tony Luck [this message]
2021-09-21  7:52     ` [tip: ras/core] x86/mce: Change to not send SIGBUS error during copy from user tip-bot2 for Tony Luck
2021-08-18  0:29   ` [PATCH v2 3/3] x86/mce: Drop copyin special case for #MC Tony Luck
2021-09-20  9:13     ` Borislav Petkov
2021-09-20 16:18       ` Luck, Tony
2021-09-20 16:37         ` Borislav Petkov
2021-09-20 16:43           ` Luck, Tony
2021-09-21  7:52     ` [tip: ras/core] " tip-bot2 for Tony Luck
2021-08-18 16:14   ` [PATCH v2 0/3] More machine check recovery fixes Luck, Tony

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