5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Russell King (Oracle) [ Upstream commit fd2dee1c6e2256f726ba33fd3083a7be0efc80d3 ] __do_user_fault() may be called with indeterminent interrupt enable state, which means we may be preemptive at this point. This causes problems when calling harden_branch_predictor(). For example, when called from a data abort, do_alignment_fault()->do_bad_area(). Move harden_branch_predictor() out of __do_user_fault() and into the calling contexts. Moving it into do_kernel_address_page_fault(), we can be sure that interrupts will be disabled here. Converting do_translation_fault() to use do_kernel_address_page_fault() rather than do_bad_area() means that we keep branch predictor handling for translation faults. Interrupts will also be disabled at this call site. do_sect_fault() needs special handling, so detect user mode accesses to kernel-addresses, and add an explicit call to branch predictor hardening. Finally, add branch predictor hardening to do_alignment() for the faulting case (user mode accessing kernel addresses) before interrupts are enabled. This should cover all cases where harden_branch_predictor() is called, ensuring that it is always has interrupts disabled, also ensuring that it is called early in each call path. [ Xie Yuanbin: At the upstream, the following patches are a patch set: 1. commit dea20281ac8822661576 ("ARM: group is_permission_fault() with is_translation_fault()") 2. commit 40b466db1dffb41f0529 ("ARM: allow __do_kernel_fault() to report execution of memory faults") 3. commit 7733bc7d299d682f2723 ("ARM: fix hash_name() fault") 4. commit fd2dee1c6e2256f726ba ("ARM: fix branch predictor hardening") patch 1. and 2. is unneeded for 5.10.y and 5.15.y . This patch backports patch 4. and simply adapts to the context differences. ] Reviewed-by: Xie Yuanbin Tested-by: Xie Yuanbin Signed-off-by: Russell King (Oracle) Signed-off-by: Xie Yuanbin Signed-off-by: Sasha Levin --- arch/arm/mm/alignment.c | 4 ++++ arch/arm/mm/fault.c | 39 ++++++++++++++++++++++++++------------- 2 files changed, 30 insertions(+), 13 deletions(-) diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c index bcefe3f51744c..758504a28c13f 100644 --- a/arch/arm/mm/alignment.c +++ b/arch/arm/mm/alignment.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include "fault.h" @@ -809,6 +810,9 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs) int thumb2_32b = 0; int fault; + if (addr >= TASK_SIZE && user_mode(regs)) + harden_branch_predictor(); + if (interrupts_enabled(regs)) local_irq_enable(); diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c index 831fc426cda1f..b186a31b3cf72 100644 --- a/arch/arm/mm/fault.c +++ b/arch/arm/mm/fault.c @@ -145,9 +145,6 @@ __do_user_fault(unsigned long addr, unsigned int fsr, unsigned int sig, { struct task_struct *tsk = current; - if (addr > TASK_SIZE) - harden_branch_predictor(); - #ifdef CONFIG_DEBUG_USER if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) || ((user_debug & UDBG_BUS) && (sig == SIGBUS))) { @@ -255,8 +252,10 @@ do_kernel_address_page_fault(struct mm_struct *mm, unsigned long addr, /* * Fault from user mode for a kernel space address. User mode * should not be faulting in kernel space, which includes the - * vector/khelper page. Send a SIGSEGV. + * vector/khelper page. Handle the branch predictor hardening + * while interrupts are still disabled, then send a SIGSEGV. */ + harden_branch_predictor(); __do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs); } else { /* @@ -421,16 +420,20 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) * We enter here because the first level page table doesn't contain * a valid entry for the address. * - * If the address is in kernel space (>= TASK_SIZE), then we are - * probably faulting in the vmalloc() area. + * If this is a user address (addr < TASK_SIZE), we handle this as a + * normal page fault. This leaves the remainder of the function to handle + * kernel address translation faults. * - * If the init_task's first level page tables contains the relevant - * entry, we copy the it to this task. If not, we send the process - * a signal, fixup the exception, or oops the kernel. + * Since user mode is not permitted to access kernel addresses, pass these + * directly to do_kernel_address_page_fault() to handle. * - * NOTE! We MUST NOT take any locks for this case. We may be in an - * interrupt or a critical region, and should only copy the information - * from the master page table, nothing more. + * Otherwise, we're probably faulting in the vmalloc() area, so try to fix + * that up. Note that we must not take any locks or enable interrupts in + * this case. + * + * If vmalloc() fixup fails, that means the non-leaf page tables did not + * contain an entry for this address, so handle this via + * do_kernel_address_page_fault(). */ #ifdef CONFIG_MMU static int __kprobes @@ -496,7 +499,8 @@ do_translation_fault(unsigned long addr, unsigned int fsr, return 0; bad_area: - do_bad_area(addr, fsr, regs); + do_kernel_address_page_fault(current->mm, addr, fsr, regs); + return 0; } #else /* CONFIG_MMU */ @@ -516,7 +520,16 @@ do_translation_fault(unsigned long addr, unsigned int fsr, static int do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { + /* + * If this is a kernel address, but from user mode, then userspace + * is trying bad stuff. Invoke the branch predictor handling. + * Interrupts are disabled here. + */ + if (addr >= TASK_SIZE && user_mode(regs)) + harden_branch_predictor(); + do_bad_area(addr, fsr, regs); + return 0; } #endif /* CONFIG_ARM_LPAE */ -- 2.53.0