Messages in this thread Patch in this message | | | Date | Mon, 5 Oct 2020 18:32:47 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 6/7] x86/mce: Recover from poison found while copying from user space |
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On Wed, Sep 30, 2020 at 04:26:10PM -0700, Tony Luck wrote: > From: Youquan Song <youquan.song@intel.com> > > Existing kernel code can only recover from a machine check on code that > is tagged in the exception table with a fault handling recovery path. > > Two new fields in the task structure to pass information from machine > check handler to the "task_work" that is queued to run before the task > returns to user mode: > > + mce_vaddr: will be initialized to the user virtual address of the fault > in the case where the fault occurred in the kernel copying data from > a user address. This is so that kill_me_maybe() can provide that > information to the user SIGBUS handler. > > + mce_kflags: copy of the struct mce.kflags needed by kill_me_maybe() > to determine if mce_vaddr is applicable to this error. > > Add code to recover from a machine check while copying data from user > space to the kernel. Action for this case is the same as if the user > touched the poison directly; unmap the page and send a SIGBUS to the task. > > Refactor the recovery code path to share common code between the "fault > in user mode" case and the "fault while copying from user" case. > > New code paths will be activated by the next patch which sets > MCE_IN_KERNEL_COPYIN. > > Signed-off-by: Youquan Song <youquan.song@intel.com> > Signed-off-by: Tony Luck <tony.luck@intel.com> > --- > arch/x86/kernel/cpu/mce/core.c | 33 +++++++++++++++++++++------------ > include/linux/sched.h | 2 ++ > 2 files changed, 23 insertions(+), 12 deletions(-)
Isn't that just simpler?
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index 4d2cf08820af..dc6c83aa2ec1 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -1261,6 +1261,21 @@ static void kill_me_maybe(struct callback_head *cb) kill_me_now(cb); } +static inline void queue_task_work(struct mce *m, int kill_it) +{ + current->mce_addr = m->addr; + current->mce_kflags = m->kflags; + current->mce_ripv = !!(m->mcgstatus & MCG_STATUS_RIPV); + current->mce_whole_page = whole_page(m); + + if (kill_it) + current->mce_kill_me.func = kill_me_now; + else + current->mce_kill_me.func = kill_me_maybe; + + task_work_add(current, ¤t->mce_kill_me, true); +} + /* * The actual machine check handler. This only handles real * exceptions when something got corrupted coming in through int 18. @@ -1402,13 +1417,8 @@ 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)); - current->mce_addr = m.addr; - current->mce_ripv = !!(m.mcgstatus & MCG_STATUS_RIPV); - current->mce_whole_page = whole_page(&m); - current->mce_kill_me.func = kill_me_maybe; - if (kill_it) - current->mce_kill_me.func = kill_me_now; - task_work_add(current, ¤t->mce_kill_me, true); + queue_task_work(&m, kill_it); + } else { /* * Handle an MCE which has happened in kernel space but from @@ -1423,6 +1433,9 @@ noinstr void do_machine_check(struct pt_regs *regs) if (!fixup_exception(regs, X86_TRAP_MC, 0, 0)) mce_panic("Failed kernel mode recovery", &m, msg); } + + if (m.kflags & MCE_IN_KERNEL_COPYIN) + queue_task_work(&m, kill_it); } out: mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); diff --git a/include/linux/sched.h b/include/linux/sched.h index e7f65573dde3..d383cf09e78f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1308,6 +1308,8 @@ struct task_struct { #endif #ifdef CONFIG_X86_MCE + void __user *mce_vaddr; + __u64 mce_kflags; u64 mce_addr; __u64 mce_ripv : 1, mce_whole_page : 1, -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
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