----- On Oct 13, 2018, at 2:34 PM, Mathieu Desnoyers [email protected] wrote:
> ----- On Oct 13, 2018, at 11:24 AM, Ard Biesheuvel [email protected] > wrote: > >> On 12 October 2018 at 23:07, Ard Biesheuvel <[email protected]> >> wrote: >>> Hi Mathieu, >>> >>> On 12 October 2018 at 22:05, Mathieu Desnoyers >>> <[email protected]> wrote: >>>> commit 46e0c9be206f ("kernel: tracepoints: add support for relative >>>> references") changes the layout of the __tracepoint_ptrs section on >>>> architectures supporting relative references. However, it does so >>>> without turning struct tracepoint * const into const int * elsewhere in >>>> the tracepoint code, which has the following side-effect: >>>> >>>> tracepoint_module_{coming,going} invoke >>>> tp_module_going_check_quiescent() with mod->tracepoints_ptrs >>>> as first argument, and computes the end address of the array >>>> for the second argument with: >>>> >>>> mod->tracepoints_ptrs + mod->num_tracepoints >>>> >>>> However, because the type of mod->tracepoint_ptrs in module.h >>>> has not been changed from pointer to int, it passes an end >>>> pointer which is twice larger than the array, causing out-of-bound >>>> array accesses. >>>> >>>> Fix this by introducing a new typedef: tracepoint_ptr_t, which >>>> is either "const int" on architectures that have PREL32 relocations, >>>> or "struct tracepoint * const" on architectures that does not have >>>> this feature. >>>> >>>> Also provide a new tracepoint_ptr_defer() static inline to >>>> encapsulate deferencing this type rather than duplicate code and >>>> ugly idefs within the for_each_tracepoint_range() implementation. >>>> >>> >>> Apologies for the breakage. FWIW, this looks like the correct approach >>> to me (and mirrors what I did for initcalls in the same series) >>> >>>> This issue appears in 4.19-rc kernels, and should ideally be fixed >>>> before the end of the rc cycle. >>>> >>> >>> +1 >>> >>>> Signed-off-by: Mathieu Desnoyers <[email protected]> >>>> Link: >>>> http://lkml.kernel.org/r/[email protected] >>>> Cc: Michael Ellerman <[email protected]> >>>> Cc: Ingo Molnar <[email protected]> >>>> Cc: Steven Rostedt (VMware) <[email protected]> >>>> Cc: Ard Biesheuvel <[email protected]> >>>> Cc: Arnd Bergmann <[email protected]> >>>> Cc: Benjamin Herrenschmidt <[email protected]> >>>> Cc: Bjorn Helgaas <[email protected]> >>>> Cc: Catalin Marinas <[email protected]> >>>> Cc: James Morris <[email protected]> >>>> Cc: James Morris <[email protected]> >>>> Cc: Jessica Yu <[email protected]> >>>> Cc: Josh Poimboeuf <[email protected]> >>>> Cc: Kees Cook <[email protected]> >>>> Cc: Nicolas Pitre <[email protected]> >>>> Cc: Paul Mackerras <[email protected]> >>>> Cc: Petr Mladek <[email protected]> >>>> Cc: Russell King <[email protected]> >>>> Cc: "Serge E. Hallyn" <[email protected]> >>>> Cc: Sergey Senozhatsky <[email protected]> >>>> Cc: Thomas Garnier <[email protected]> >>>> Cc: Thomas Gleixner <[email protected]> >>>> Cc: Will Deacon <[email protected]> >>>> Cc: Andrew Morton <[email protected]> >>>> Cc: Linus Torvalds <[email protected]> >>>> Cc: Greg Kroah-Hartman <[email protected]> >>> >>> Acked-by: Ard Biesheuvel <[email protected]> >>> >> >> This fixes the build breakage for me that kbuild test robot reports. >> >> diff --git a/include/linux/module.h b/include/linux/module.h >> index cdab2451d6be..e19ae08c7fb8 100644 >> --- a/include/linux/module.h >> +++ b/include/linux/module.h >> @@ -20,6 +20,7 @@ >> #include <linux/export.h> >> #include <linux/rbtree_latch.h> >> #include <linux/error-injection.h> >> +#include <linux/tracepoint-defs.h> > > You've beat me to it :) I'll fold this change in a v2 of the patch, Digging a bit deeper into module.c, I notice it's not really an out-of-bound access that is generated by this issue, because setting mod->num_tracepoints is done in by module.c like this: mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs", sizeof(*mod->tracepoints_ptrs), &mod->num_tracepoints); So basically, since sizeof(*mod->tracepoints_ptrs) is a pointer size (rather than sizeof(int)), num_tracepoints is erroneously set to half the size it should be on 64-bit arch. So we an odd number of tracepoints, we lose the last tracepoint due to effect of integer division. So in the module going notifier: for_each_tracepoint_range(mod->tracepoints_ptrs, mod->tracepoints_ptrs + mod->num_tracepoints, tp_module_going_check_quiescent, NULL); the expression (mod->tracepoints_ptrs + mod->num_tracepoints) actually evaluates to something within the bounds of the array, but miss the last tracepoint if the number of tracepoints is odd on 64-bit arch. So I'll also update the patch changelog in v2. Given it does not change the patch content, I'll keep your acked-by. Please let me know if you spot anything. Thanks, Mathieu > > Thanks! > > Mathieu > >> >> #include <linux/percpu.h> >> #include <asm/module.h> >> >> >> >> >> >>>> --- >>>> include/linux/module.h | 2 +- >>>> include/linux/tracepoint-defs.h | 6 ++++++ >>>> include/linux/tracepoint.h | 36 +++++++++++++++++++++------------ >>>> kernel/tracepoint.c | 24 ++++++++-------------- >>>> 4 files changed, 38 insertions(+), 30 deletions(-) >>>> >>>> diff --git a/include/linux/module.h b/include/linux/module.h >>>> index f807f15bebbe..cdab2451d6be 100644 >>>> --- a/include/linux/module.h >>>> +++ b/include/linux/module.h >>>> @@ -430,7 +430,7 @@ struct module { >>>> >>>> #ifdef CONFIG_TRACEPOINTS >>>> unsigned int num_tracepoints; >>>> - struct tracepoint * const *tracepoints_ptrs; >>>> + tracepoint_ptr_t *tracepoints_ptrs; >>>> #endif >>>> #ifdef HAVE_JUMP_LABEL >>>> struct jump_entry *jump_entries; >>>> diff --git a/include/linux/tracepoint-defs.h >>>> b/include/linux/tracepoint-defs.h >>>> index 22c5a46e9693..49ba9cde7e4b 100644 >>>> --- a/include/linux/tracepoint-defs.h >>>> +++ b/include/linux/tracepoint-defs.h >>>> @@ -35,6 +35,12 @@ struct tracepoint { >>>> struct tracepoint_func __rcu *funcs; >>>> }; >>>> >>>> +#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS >>>> +typedef const int tracepoint_ptr_t; >>>> +#else >>>> +typedef struct tracepoint * const tracepoint_ptr_t; >>>> +#endif >>>> + >>>> struct bpf_raw_event_map { >>>> struct tracepoint *tp; >>>> void *bpf_func; >>>> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h >>>> index 041f7e56a289..538ba1a58f5b 100644 >>>> --- a/include/linux/tracepoint.h >>>> +++ b/include/linux/tracepoint.h >>>> @@ -99,6 +99,29 @@ extern void syscall_unregfunc(void); >>>> #define TRACE_DEFINE_ENUM(x) >>>> #define TRACE_DEFINE_SIZEOF(x) >>>> >>>> +#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS >>>> +static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) >>>> +{ >>>> + return offset_to_ptr(p); >>>> +} >>>> + >>>> +#define __TRACEPOINT_ENTRY(name) \ >>>> + asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \ >>>> + " .balign 4 \n" \ >>>> + " .long __tracepoint_" #name " - . \n" \ >>>> + " .previous \n") >>>> +#else >>>> +static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) >>>> +{ >>>> + return *p; >>>> +} >>>> + >>>> +#define __TRACEPOINT_ENTRY(name) \ >>>> + static tracepoint_ptr_t __tracepoint_ptr_##name __used \ >>>> + __attribute__((section("__tracepoints_ptrs"))) = \ >>>> + &__tracepoint_##name >>>> +#endif >>>> + >>>> #endif /* _LINUX_TRACEPOINT_H */ >>>> >>>> /* >>>> @@ -253,19 +276,6 @@ extern void syscall_unregfunc(void); >>>> return static_key_false(&__tracepoint_##name.key); \ >>>> } >>>> >>>> -#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS >>>> -#define __TRACEPOINT_ENTRY(name) \ >>>> - asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \ >>>> - " .balign 4 \n" \ >>>> - " .long __tracepoint_" #name " - . \n" \ >>>> - " .previous \n") >>>> -#else >>>> -#define __TRACEPOINT_ENTRY(name) \ >>>> - static struct tracepoint * const __tracepoint_ptr_##name __used \ >>>> - __attribute__((section("__tracepoints_ptrs"))) = \ >>>> - &__tracepoint_##name >>>> -#endif >>>> - >>>> /* >>>> * We have no guarantee that gcc and the linker won't up-align the >>>> tracepoint >>>> * structures, so we create an array of pointers that will be used for >>>> iteration >>>> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c >>>> index bf2c06ef9afc..a3be42304485 100644 >>>> --- a/kernel/tracepoint.c >>>> +++ b/kernel/tracepoint.c >>>> @@ -28,8 +28,8 @@ >>>> #include <linux/sched/task.h> >>>> #include <linux/static_key.h> >>>> >>>> -extern struct tracepoint * const __start___tracepoints_ptrs[]; >>>> -extern struct tracepoint * const __stop___tracepoints_ptrs[]; >>>> +extern tracepoint_ptr_t __start___tracepoints_ptrs[]; >>>> +extern tracepoint_ptr_t __stop___tracepoints_ptrs[]; >>>> >>>> DEFINE_SRCU(tracepoint_srcu); >>>> EXPORT_SYMBOL_GPL(tracepoint_srcu); >>>> @@ -371,25 +371,17 @@ int tracepoint_probe_unregister(struct tracepoint >>>> *tp, >>>> void *probe, void *data) >>>> } >>>> EXPORT_SYMBOL_GPL(tracepoint_probe_unregister); >>>> >>>> -static void for_each_tracepoint_range(struct tracepoint * const *begin, >>>> - struct tracepoint * const *end, >>>> +static void for_each_tracepoint_range( >>>> + tracepoint_ptr_t *begin, tracepoint_ptr_t *end, >>>> void (*fct)(struct tracepoint *tp, void *priv), >>>> void *priv) >>>> { >>>> + tracepoint_ptr_t *iter; >>>> + >>>> if (!begin) >>>> return; >>>> - >>>> - if (IS_ENABLED(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)) { >>>> - const int *iter; >>>> - >>>> - for (iter = (const int *)begin; iter < (const int *)end; >>>> iter++) >>>> - fct(offset_to_ptr(iter), priv); >>>> - } else { >>>> - struct tracepoint * const *iter; >>>> - >>>> - for (iter = begin; iter < end; iter++) >>>> - fct(*iter, priv); >>>> - } >>>> + for (iter = begin; iter < end; iter++) >>>> + fct(tracepoint_ptr_deref(iter), priv); >>>> } >>>> >>>> #ifdef CONFIG_MODULES >>>> -- >>>> 2.17.1 > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
