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addr-map.c
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/* -*- linux-c -*- * Map of addresses to disallow. * Copyright (C) 2005-2016 Red Hat Inc. * * This file is part of systemtap, and is free software. You can * redistribute it and/or modify it under the terms of the GNU General * Public License (GPL); either version 2, or (at your option) any * later version. */ #ifndef _STAPLINUX_ADDR_MAP_C_ #define _STAPLINUX_ADDR_MAP_C_ 1 /** @file addr-map * @brief Implements functions used by the deref macro to blacklist * certain addresses. */ // PR12970 (populate runtime/bad-addr database) hasn't been // fixed. Until we're ready to populate the bad address database, // let's provide a "junior" version of lookup_bad_addr(), since that // will allow us to skip grabbing the lock and searching the empty // list. // // See <https://sourceware.org/bugzilla/show_bug.cgi?id=12970> for // more details. #include <linux/uaccess.h> #ifndef PR12970 #if ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPDEV) && \ ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPSYS) #include <asm/processor.h> /* For TASK_SIZE */ #endif static int lookup_bad_addr(const int type, const unsigned long addr, const size_t size) { /* Is this a valid memory access? * * Note we're using access_ok() here. This is only supposed to be * called when we're in task context. Occasionally lookup_bad_addr() * gets called when not in task context. If in_task() exists, only * call access_ok() when we're in task context (otherwise we'll get * a kernel warning). If we aren't in task context, we'll just do a * range check. */ #if !defined(in_task) if (size == 0 || ULONG_MAX - addr < size - 1 || !access_ok(type, (void *)addr, size)) return 1; #else if (size == 0 || ULONG_MAX - addr < size - 1 || (in_task() && !access_ok(type, (void *)addr, size)) || (!in_task() #if defined(user_addr_max) && ((user_addr_max() - size) < addr) #endif )) return 1; #endif #if ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPDEV) && \ ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPSYS) /* Unprivileged users must not access memory while the context does not refer to their own process. */ if (! is_myproc ()) return 1; /* Unprivileged users must not access kernel space memory. */ if (addr + size > TASK_SIZE) return 1; #endif return 0; } #else /* PR12970 */ struct addr_map_entry { unsigned long min; unsigned long max; }; struct addr_map { size_t size; struct addr_map_entry entries[0]; }; static STP_DEFINE_RWLOCK(addr_map_lock); static struct addr_map* blackmap; /* Find address of entry where we can insert a new one. */ static size_t upper_bound(unsigned long addr, struct addr_map* map) { size_t start = 0; size_t end = map->size; struct addr_map_entry *entry = 0; if (end == 0) return 0; do { size_t new_idx; if (addr < map->entries[start].min) return start; if (addr >= map->entries[end-1].max) return end; new_idx = (end + start) / 2; entry = &map->entries[new_idx]; if (addr < entry->min) end = new_idx; else start = new_idx + 1; } while (end != start); return entry - &map->entries[0]; } /* Search for an entry in the given map which overlaps the range specified by addr and size. */ static struct addr_map_entry* lookup_addr_aux(unsigned long addr, size_t size, struct addr_map* map) { size_t start = 0; size_t end; /* No map? No matching entry. */ if (!map) return 0; /* Empty map? No matching entry. */ if (map->size == 0) return 0; /* Use binary search on the sorted map entries. */ end = map->size; do { int entry_idx; struct addr_map_entry *entry = 0; /* If the target range is beyond those of the remaining entries in the map, then a matching entry will not be found */ if (addr + size <= map->entries[start].min || addr >= map->entries[end - 1].max) return 0; /* Choose the map entry at the mid point of the remaining entries. */ entry_idx = (end + start) / 2; entry = &map->entries[entry_idx]; /* If our range overlaps the range of this entry, then we have a match. */ if (addr + size > entry->min && addr < entry->max) return entry; /* If our range is below the range of this entry, then cull the entries above this entry, otherwise cull the entries below it. */ if (addr + size <= entry->min) end = entry_idx; else start = entry_idx + 1; } while (start < end); return 0; } #if ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPDEV) && \ ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPSYS) #include <asm/processor.h> /* For TASK_SIZE */ #endif static int lookup_bad_addr(const int type, const unsigned long addr, const size_t size) { struct addr_map_entry* result = 0; unsigned long flags; /* Is this a valid memory access? */ if (size == 0 || ULONG_MAX - addr < size - 1 || !access_ok(type, (void *)addr, size)) return 1; #if ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPDEV) && \ ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPSYS) /* Unprivileged users must not access memory while the context does not refer to their own process. */ if (! is_myproc ()) return 1; /* Unprivileged users must not access kernel space memory. */ if (addr + size > TASK_SIZE) return 1; #endif /* Search for the given range in the black-listed map. */ stp_read_lock_irqsave(&addr_map_lock, flags); result = lookup_addr_aux(addr, size, blackmap); stp_read_unlock_irqrestore(&addr_map_lock, flags); if (result) return 1; else return 0; } static int add_bad_addr_entry(unsigned long min_addr, unsigned long max_addr, struct addr_map_entry** existing_min, struct addr_map_entry** existing_max) { struct addr_map* new_map = 0; struct addr_map* old_map = 0; struct addr_map_entry* min_entry = 0; struct addr_map_entry* max_entry = 0; struct addr_map_entry* new_entry = 0; size_t existing = 0; unsigned long flags; /* Loop allocating memory for a new entry in the map. */ while (1) { size_t old_size = 0; stp_write_lock_irqsave(&addr_map_lock, flags); old_map = blackmap; if (old_map) old_size = old_map->size; /* Either this is the first time through the loop, or we allocated a map previous time, but someone has come in and added an entry while we were sleeping. */ if (!new_map || (new_map && new_map->size < old_size + 1)) { stp_write_unlock_irqrestore(&addr_map_lock, flags); if (new_map) { _stp_kfree(new_map); new_map = 0; } new_map = _stp_kmalloc(sizeof(*new_map) + sizeof(*new_entry) * (old_size + 1)); if (!new_map) return -ENOMEM; new_map->size = old_size + 1; } else break; } if (!blackmap) { existing = 0; } else { min_entry = lookup_addr_aux(min_addr, 1, blackmap); max_entry = lookup_addr_aux(max_addr, 1, blackmap); if (min_entry || max_entry) { if (existing_min) *existing_min = min_entry; if (existing_max) *existing_max = max_entry; stp_write_unlock_irqrestore(&addr_map_lock, flags); _stp_kfree(new_map); return 1; } existing = upper_bound(min_addr, old_map); } new_entry = &new_map->entries[existing]; new_entry->min = min_addr; new_entry->max = max_addr; if (old_map) { memcpy(&new_map->entries, old_map->entries, existing * sizeof(*new_entry)); if (old_map->size > existing) memcpy(new_entry + 1, &old_map->entries[existing], (old_map->size - existing) * sizeof(*new_entry)); } blackmap = new_map; stp_write_unlock_irqrestore(&addr_map_lock, flags); if (old_map) _stp_kfree(old_map); return 0; } static void delete_bad_addr_entry(struct addr_map_entry* entry) { } #endif /* PR12970 */ #endif /* _STAPLINUX_ADDR_MAP_C_ */