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list: Split list_del() debug checking into separate function
Similar to the list_add() debug consolidation, this commit consolidates the debug checking performed during CONFIG_DEBUG_LIST into a new __list_del_entry_valid() function, and stops list updates when corruption is found. Refactored from same hardening in PaX and Grsecurity. Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Rik van Riel <riel@redhat.com>
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@ -32,6 +32,7 @@ static inline void INIT_LIST_HEAD(struct list_head *list)
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extern bool __list_add_valid(struct list_head *new,
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struct list_head *prev,
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struct list_head *next);
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extern bool __list_del_entry_valid(struct list_head *entry);
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#else
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static inline bool __list_add_valid(struct list_head *new,
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struct list_head *prev,
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@ -39,6 +40,10 @@ static inline bool __list_add_valid(struct list_head *new,
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{
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return true;
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}
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static inline bool __list_del_entry_valid(struct list_head *entry)
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{
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return true;
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}
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#endif
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/*
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@ -106,22 +111,20 @@ static inline void __list_del(struct list_head * prev, struct list_head * next)
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* Note: list_empty() on entry does not return true after this, the entry is
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* in an undefined state.
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*/
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#ifndef CONFIG_DEBUG_LIST
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static inline void __list_del_entry(struct list_head *entry)
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{
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if (!__list_del_entry_valid(entry))
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return;
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__list_del(entry->prev, entry->next);
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}
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static inline void list_del(struct list_head *entry)
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{
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__list_del(entry->prev, entry->next);
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__list_del_entry(entry);
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entry->next = LIST_POISON1;
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entry->prev = LIST_POISON2;
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}
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#else
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extern void __list_del_entry(struct list_head *entry);
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extern void list_del(struct list_head *entry);
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#endif
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/**
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* list_replace - replace old entry by new one
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@ -39,41 +39,34 @@ bool __list_add_valid(struct list_head *new, struct list_head *prev,
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}
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EXPORT_SYMBOL(__list_add_valid);
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void __list_del_entry(struct list_head *entry)
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bool __list_del_entry_valid(struct list_head *entry)
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{
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struct list_head *prev, *next;
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prev = entry->prev;
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next = entry->next;
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if (WARN(next == LIST_POISON1,
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"list_del corruption, %p->next is LIST_POISON1 (%p)\n",
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entry, LIST_POISON1) ||
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WARN(prev == LIST_POISON2,
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"list_del corruption, %p->prev is LIST_POISON2 (%p)\n",
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entry, LIST_POISON2) ||
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WARN(prev->next != entry,
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"list_del corruption. prev->next should be %p, "
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"but was %p\n", entry, prev->next) ||
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WARN(next->prev != entry,
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"list_del corruption. next->prev should be %p, "
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"but was %p\n", entry, next->prev))
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return;
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if (unlikely(next == LIST_POISON1)) {
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WARN(1, "list_del corruption, %p->next is LIST_POISON1 (%p)\n",
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entry, LIST_POISON1);
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return false;
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}
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if (unlikely(prev == LIST_POISON2)) {
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WARN(1, "list_del corruption, %p->prev is LIST_POISON2 (%p)\n",
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entry, LIST_POISON2);
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return false;
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}
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if (unlikely(prev->next != entry)) {
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WARN(1, "list_del corruption. prev->next should be %p, but was %p\n",
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entry, prev->next);
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return false;
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}
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if (unlikely(next->prev != entry)) {
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WARN(1, "list_del corruption. next->prev should be %p, but was %p\n",
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entry, next->prev);
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return false;
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}
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return true;
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__list_del(prev, next);
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}
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EXPORT_SYMBOL(__list_del_entry);
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/**
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* list_del - deletes entry from list.
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* @entry: the element to delete from the list.
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* Note: list_empty on entry does not return true after this, the entry is
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* in an undefined state.
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*/
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void list_del(struct list_head *entry)
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{
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__list_del_entry(entry);
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entry->next = LIST_POISON1;
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entry->prev = LIST_POISON2;
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}
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EXPORT_SYMBOL(list_del);
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EXPORT_SYMBOL(__list_del_entry_valid);
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