-/* Helper to check whether a uaccess fault indicates a kernel bug. */
-static bool bogus_uaccess(struct pt_regs *regs, int trapnr,
- unsigned long fault_addr)
-{
- /* This is the normal case: #PF with a fault address in userspace. */
- if (trapnr == X86_TRAP_PF && fault_addr < TASK_SIZE_MAX)
- return false;
-
- /*
- * This code can be reached for machine checks, but only if the #MC
- * handler has already decided that it looks like a candidate for fixup.
- * This e.g. happens when attempting to access userspace memory which
- * the CPU can't access because of uncorrectable bad memory.
- */
- if (trapnr == X86_TRAP_MC)
- return false;
-
- /*
- * There are two remaining exception types we might encounter here:
- * - #PF for faulting accesses to kernel addresses
- * - #GP for faulting accesses to noncanonical addresses
- * Complain about anything else.
- */
- if (trapnr != X86_TRAP_PF && trapnr != X86_TRAP_GP) {
- WARN(1, "unexpected trap %d in uaccess\n", trapnr);
- return false;
- }
-
- /*
- * This is a faulting memory access in kernel space, on a kernel
- * address, in a usercopy function. This can e.g. be caused by improper
- * use of helpers like __put_user and by improper attempts to access
- * userspace addresses in KERNEL_DS regions.
- * The one (semi-)legitimate exception are probe_kernel_{read,write}(),
- * which can be invoked from places like kgdb, /dev/mem (for reading)
- * and privileged BPF code (for reading).
- * The probe_kernel_*() functions set the kernel_uaccess_faults_ok flag
- * to tell us that faulting on kernel addresses, and even noncanonical
- * addresses, in a userspace accessor does not necessarily imply a
- * kernel bug, root might just be doing weird stuff.
- */
- if (current->kernel_uaccess_faults_ok)
- return false;
-
- /* This is bad. Refuse the fixup so that we go into die(). */
- if (trapnr == X86_TRAP_PF) {
- pr_emerg("BUG: pagefault on kernel address 0x%lx in non-whitelisted uaccess\n",
- fault_addr);
- } else {
- pr_emerg("BUG: GPF in non-whitelisted uaccess (non-canonical address?)\n");
- }
- return true;
-}
-