----- 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, 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
