From 36aa1e6779c3c6f8e0d4552544214f5cffe3c287 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Fri, 10 Feb 2023 22:16:03 +0100 Subject: [PATCH] lib/stacktrace, kasan, kmsan: rework extra_bits interface The current implementation of the extra_bits interface is confusing: passing extra_bits to __stack_depot_save makes it seem that the extra bits are somehow stored in stack depot. In reality, they are only embedded into a stack depot handle and are not used within stack depot. Drop the extra_bits argument from __stack_depot_save and instead provide a new stack_depot_set_extra_bits function (similar to the exsiting stack_depot_get_extra_bits) that saves extra bits into a stack depot handle. Update the callers of __stack_depot_save to use the new interace. This change also fixes a minor issue in the old code: __stack_depot_save does not return NULL if saving stack trace fails and extra_bits is used. Link: https://lkml.kernel.org/r/317123b5c05e2f82854fc55d8b285e0869d3cb77.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Alexander Potapenko Signed-off-by: Andrew Morton --- include/linux/stackdepot.h | 4 +++- lib/stackdepot.c | 42 +++++++++++++++++++++++++++++++++--------- mm/kasan/common.c | 2 +- mm/kmsan/core.c | 10 +++++++--- 4 files changed, 44 insertions(+), 14 deletions(-) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index c4e3abc..267f4b2 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -57,7 +57,6 @@ static inline int stack_depot_early_init(void) { return 0; } depot_stack_handle_t __stack_depot_save(unsigned long *entries, unsigned int nr_entries, - unsigned int extra_bits, gfp_t gfp_flags, bool can_alloc); depot_stack_handle_t stack_depot_save(unsigned long *entries, @@ -71,6 +70,9 @@ void stack_depot_print(depot_stack_handle_t stack); int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, int spaces); +depot_stack_handle_t __must_check stack_depot_set_extra_bits( + depot_stack_handle_t handle, unsigned int extra_bits); + unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle); #endif diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 4df162a..8c6e4e9 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -357,7 +357,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket, * * @entries: Pointer to storage array * @nr_entries: Size of the storage array - * @extra_bits: Flags to store in unused bits of depot_stack_handle_t * @alloc_flags: Allocation gfp flags * @can_alloc: Allocate stack pools (increased chance of failure if false) * @@ -369,10 +368,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket, * If the stack trace in @entries is from an interrupt, only the portion up to * interrupt entry is saved. * - * Additional opaque flags can be passed in @extra_bits, stored in the unused - * bits of the stack handle, and retrieved using stack_depot_get_extra_bits() - * without calling stack_depot_fetch(). - * * Context: Any context, but setting @can_alloc to %false is required if * alloc_pages() cannot be used from the current context. Currently * this is the case from contexts where neither %GFP_ATOMIC nor @@ -382,7 +377,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket, */ depot_stack_handle_t __stack_depot_save(unsigned long *entries, unsigned int nr_entries, - unsigned int extra_bits, gfp_t alloc_flags, bool can_alloc) { struct stack_record *found = NULL, **bucket; @@ -471,8 +465,6 @@ exit: if (found) retval.handle = found->handle.handle; fast_exit: - retval.extra = extra_bits; - return retval.handle; } EXPORT_SYMBOL_GPL(__stack_depot_save); @@ -493,7 +485,7 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int nr_entries, gfp_t alloc_flags) { - return __stack_depot_save(entries, nr_entries, 0, alloc_flags, true); + return __stack_depot_save(entries, nr_entries, alloc_flags, true); } EXPORT_SYMBOL_GPL(stack_depot_save); @@ -576,6 +568,38 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, } EXPORT_SYMBOL_GPL(stack_depot_snprint); +/** + * stack_depot_set_extra_bits - Set extra bits in a stack depot handle + * + * @handle: Stack depot handle returned from stack_depot_save() + * @extra_bits: Value to set the extra bits + * + * Return: Stack depot handle with extra bits set + * + * Stack depot handles have a few unused bits, which can be used for storing + * user-specific information. These bits are transparent to the stack depot. + */ +depot_stack_handle_t __must_check stack_depot_set_extra_bits( + depot_stack_handle_t handle, unsigned int extra_bits) +{ + union handle_parts parts = { .handle = handle }; + + /* Don't set extra bits on empty handles. */ + if (!handle) + return 0; + + parts.extra = extra_bits; + return parts.handle; +} +EXPORT_SYMBOL(stack_depot_set_extra_bits); + +/** + * stack_depot_get_extra_bits - Retrieve extra bits from a stack depot handle + * + * @handle: Stack depot handle with extra bits saved + * + * Return: Extra bits retrieved from the stack depot handle + */ unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle) { union handle_parts parts = { .handle = handle }; diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 1e7336a..b376a5d 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -43,7 +43,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc) unsigned int nr_entries; nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); - return __stack_depot_save(entries, nr_entries, 0, flags, can_alloc); + return __stack_depot_save(entries, nr_entries, flags, can_alloc); } void kasan_set_track(struct kasan_track *track, gfp_t flags) diff --git a/mm/kmsan/core.c b/mm/kmsan/core.c index 112dce1..f710257 100644 --- a/mm/kmsan/core.c +++ b/mm/kmsan/core.c @@ -69,13 +69,15 @@ depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, { unsigned long entries[KMSAN_STACK_DEPTH]; unsigned int nr_entries; + depot_stack_handle_t handle; nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0); /* Don't sleep (see might_sleep_if() in __alloc_pages_nodemask()). */ flags &= ~__GFP_DIRECT_RECLAIM; - return __stack_depot_save(entries, nr_entries, extra, flags, true); + handle = __stack_depot_save(entries, nr_entries, flags, true); + return stack_depot_set_extra_bits(handle, extra); } /* Copy the metadata following the memmove() behavior. */ @@ -215,6 +217,7 @@ depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id) u32 extra_bits; int depth; bool uaf; + depot_stack_handle_t handle; if (!id) return id; @@ -250,8 +253,9 @@ depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id) * positives when __stack_depot_save() passes it to instrumented code. */ kmsan_internal_unpoison_memory(entries, sizeof(entries), false); - return __stack_depot_save(entries, ARRAY_SIZE(entries), extra_bits, - GFP_ATOMIC, true); + handle = __stack_depot_save(entries, ARRAY_SIZE(entries), GFP_ATOMIC, + true); + return stack_depot_set_extra_bits(handle, extra_bits); } void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b, -- 2.7.4