| Message ID | 1471393229-27182-2-git-send-email-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 16 Aug 2016 17:20:25 -0700 Kees Cook <keescook@chromium.org> wrote: > Right now, __list_add() code is repeated either in list.h or in > list_debug.c, but only the debug checks are the different part. This > extracts the checking into a separate function and consolidates > __list_add(). Additionally this __list_add_debug() will stop list > manipulations if a corruption is detected, instead of allowing for further > corruption that may lead to even worse conditions. > > This is slight refactoring of the same hardening done in PaX and Grsecurity. > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > include/linux/list.h | 22 ++++++++++++++++------ > lib/list_debug.c | 48 +++++++++++++++++++++++------------------------- > 2 files changed, 39 insertions(+), 31 deletions(-) > > diff --git a/include/linux/list.h b/include/linux/list.h > index 5183138aa932..0ed58591538e 100644 > --- a/include/linux/list.h > +++ b/include/linux/list.h > @@ -28,27 +28,37 @@ static inline void INIT_LIST_HEAD(struct list_head *list) > list->prev = list; > } > > +#ifdef CONFIG_DEBUG_LIST > +extern bool __list_add_valid(struct list_head *new, > + struct list_head *prev, > + struct list_head *next); > +#else > +static inline bool __list_add_valid(struct list_head *new, > + struct list_head *prev, > + struct list_head *next) > +{ > + return true; > +} > +#endif > + > /* > * Insert a new entry between two known consecutive entries. > * > * This is only for internal list manipulation where we know > * the prev/next entries already! > */ > -#ifndef CONFIG_DEBUG_LIST > static inline void __list_add(struct list_head *new, > struct list_head *prev, > struct list_head *next) > { > + if (!__list_add_valid(new, prev, next)) > + return; > + > next->prev = new; > new->next = next; > new->prev = prev; > WRITE_ONCE(prev->next, new); > } > -#else > -extern void __list_add(struct list_head *new, > - struct list_head *prev, > - struct list_head *next); > -#endif > > /** > * list_add - add a new entry > diff --git a/lib/list_debug.c b/lib/list_debug.c > index 3859bf63561c..149dd57b583b 100644 > --- a/lib/list_debug.c > +++ b/lib/list_debug.c > @@ -2,8 +2,7 @@ > * Copyright 2006, Red Hat, Inc., Dave Jones > * Released under the General Public License (GPL). > * > - * This file contains the linked list implementations for > - * DEBUG_LIST. > + * This file contains the linked list validation for DEBUG_LIST. > */ > > #include <linux/export.h> > @@ -13,33 +12,32 @@ > #include <linux/rculist.h> > > /* > - * Insert a new entry between two known consecutive entries. > - * > - * This is only for internal list manipulation where we know > - * the prev/next entries already! > + * Check that the data structures for the list manipulations are reasonably > + * valid. Failures here indicate memory corruption (and possibly an exploit > + * attempt). > */ > > -void __list_add(struct list_head *new, > - struct list_head *prev, > - struct list_head *next) > +bool __list_add_valid(struct list_head *new, struct list_head *prev, > + struct list_head *next) > { > - WARN(next->prev != prev, > - "list_add corruption. next->prev should be " > - "prev (%p), but was %p. (next=%p).\n", > - prev, next->prev, next); > - WARN(prev->next != next, > - "list_add corruption. prev->next should be " > - "next (%p), but was %p. (prev=%p).\n", > - next, prev->next, prev); > - WARN(new == prev || new == next, > - "list_add double add: new=%p, prev=%p, next=%p.\n", > - new, prev, next); > - next->prev = new; > - new->next = next; > - new->prev = prev; > - WRITE_ONCE(prev->next, new); > + if (unlikely(next->prev != prev)) { > + WARN(1, "list_add corruption. next->prev should be prev (%p), but was %p. (next=%p).\n", > + prev, next->prev, next); > + return false; BTW, WARN() does return the result, thus you could have just wrapped the if () around them: if (WARN(next->prev != prev, "list_add corruption. next->prev should be prev (%p), but was %p. (next=%p).\n", prev, next->prev, next)) return; Just FYI. -- Steve > + } > + if (unlikely(prev->next != next)) { > + WARN(1, "list_add corruption. prev->next should be next (%p), but was %p. (prev=%p).\n", > + next, prev->next, prev); > + return false; > + } > + if (unlikely(new == prev || new == next)) { > + WARN(1, "list_add double add: new=%p, prev=%p, next=%p.\n", > + new, prev, next); > + return false; > + } > + return true; > } > -EXPORT_SYMBOL(__list_add); > +EXPORT_SYMBOL(__list_add_valid); > > void __list_del_entry(struct list_head *entry) > {
diff --git a/include/linux/list.h b/include/linux/list.h index 5183138aa932..0ed58591538e 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -28,27 +28,37 @@ static inline void INIT_LIST_HEAD(struct list_head *list) list->prev = list; } +#ifdef CONFIG_DEBUG_LIST +extern bool __list_add_valid(struct list_head *new, + struct list_head *prev, + struct list_head *next); +#else +static inline bool __list_add_valid(struct list_head *new, + struct list_head *prev, + struct list_head *next) +{ + return true; +} +#endif + /* * Insert a new entry between two known consecutive entries. * * This is only for internal list manipulation where we know * the prev/next entries already! */ -#ifndef CONFIG_DEBUG_LIST static inline void __list_add(struct list_head *new, struct list_head *prev, struct list_head *next) { + if (!__list_add_valid(new, prev, next)) + return; + next->prev = new; new->next = next; new->prev = prev; WRITE_ONCE(prev->next, new); } -#else -extern void __list_add(struct list_head *new, - struct list_head *prev, - struct list_head *next); -#endif /** * list_add - add a new entry diff --git a/lib/list_debug.c b/lib/list_debug.c index 3859bf63561c..149dd57b583b 100644 --- a/lib/list_debug.c +++ b/lib/list_debug.c @@ -2,8 +2,7 @@ * Copyright 2006, Red Hat, Inc., Dave Jones * Released under the General Public License (GPL). * - * This file contains the linked list implementations for - * DEBUG_LIST. + * This file contains the linked list validation for DEBUG_LIST. */ #include <linux/export.h> @@ -13,33 +12,32 @@ #include <linux/rculist.h> /* - * Insert a new entry between two known consecutive entries. - * - * This is only for internal list manipulation where we know - * the prev/next entries already! + * Check that the data structures for the list manipulations are reasonably + * valid. Failures here indicate memory corruption (and possibly an exploit + * attempt). */ -void __list_add(struct list_head *new, - struct list_head *prev, - struct list_head *next) +bool __list_add_valid(struct list_head *new, struct list_head *prev, + struct list_head *next) { - WARN(next->prev != prev, - "list_add corruption. next->prev should be " - "prev (%p), but was %p. (next=%p).\n", - prev, next->prev, next); - WARN(prev->next != next, - "list_add corruption. prev->next should be " - "next (%p), but was %p. (prev=%p).\n", - next, prev->next, prev); - WARN(new == prev || new == next, - "list_add double add: new=%p, prev=%p, next=%p.\n", - new, prev, next); - next->prev = new; - new->next = next; - new->prev = prev; - WRITE_ONCE(prev->next, new); + if (unlikely(next->prev != prev)) { + WARN(1, "list_add corruption. next->prev should be prev (%p), but was %p. (next=%p).\n", + prev, next->prev, next); + return false; + } + if (unlikely(prev->next != next)) { + WARN(1, "list_add corruption. prev->next should be next (%p), but was %p. (prev=%p).\n", + next, prev->next, prev); + return false; + } + if (unlikely(new == prev || new == next)) { + WARN(1, "list_add double add: new=%p, prev=%p, next=%p.\n", + new, prev, next); + return false; + } + return true; } -EXPORT_SYMBOL(__list_add); +EXPORT_SYMBOL(__list_add_valid); void __list_del_entry(struct list_head *entry) {
Right now, __list_add() code is repeated either in list.h or in list_debug.c, but only the debug checks are the different part. This extracts the checking into a separate function and consolidates __list_add(). Additionally this __list_add_debug() will stop list manipulations if a corruption is detected, instead of allowing for further corruption that may lead to even worse conditions. This is slight refactoring of the same hardening done in PaX and Grsecurity. Signed-off-by: Kees Cook <keescook@chromium.org> --- include/linux/list.h | 22 ++++++++++++++++------ lib/list_debug.c | 48 +++++++++++++++++++++++------------------------- 2 files changed, 39 insertions(+), 31 deletions(-)