The following commit has been merged into the ras/core branch of tip: Commit-ID: a6e3cf70b772541c2388abdb86e5a562cfe18e63 Gitweb: https://git.kernel.org/tip/a6e3cf70b772541c2388abdb86e5a562cfe18e63 Author: Tony Luck <tony.luck@xxxxxxxxx> AuthorDate: Tue, 17 Aug 2021 17:29:41 -07:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Mon, 20 Sep 2021 10:55:41 +02:00 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: Tony Luck <tony.luck@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lkml.kernel.org/r/20210818002942.1607544-3-tony.luck@xxxxxxxxx --- 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 193204a..69768fe 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -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); - } + 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);
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