Commit a6e3cf70 authored by Tony Luck's avatar Tony Luck Committed by Borislav Petkov
Browse files

x86/mce: Change to not send SIGBUS error during copy from user 



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: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210818002942.1607544-3-tony.luck@intel.com
parent e4e737bb

arch/x86/kernel/cpu/mce/core.c

+20 −15
Original line number Diff line number Diff line
@@ -1272,7 +1272,7 @@ 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;
@@ -1286,15 +1286,21 @@ 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);

}



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;
@@ -1304,11 +1310,7 @@ 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 likely overkill. Don't expect more than two faults before task_work() */
@@ -1459,7 +1461,10 @@ 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 {

		/*
@@ -1477,7 +1482,7 @@ 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);