From: Catalin Marinas <catalin.marinas@xxxxxxx> Subject: mm: kmemleak: treat vm_struct as alternative reference to vmalloc'ed objects Kmemleak requires that vmalloc'ed objects have a minimum reference count of 2: one in the corresponding vm_struct object and the other owned by the vmalloc() caller. There are cases, however, where the original vmalloc() returned pointer is lost and, instead, a pointer to vm_struct is stored (see free_thread_stack()). Kmemleak currently reports such objects as leaks. This patch adds support for treating any surplus references to an object as additional references to a specified object. It introduces the kmemleak_vmalloc() API function which takes a vm_struct pointer and sets its surplus reference passing to the actual vmalloc() returned pointer. The __vmalloc_node_range() calling site has been modified accordingly. Link: http://lkml.kernel.org/r/1495726937-23557-4-git-send-email-catalin.marinas@xxxxxxx Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Reported-by: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/dev-tools/kmemleak.rst | 1 include/linux/kmemleak.h | 7 + mm/kmemleak.c | 93 +++++++++++++++++++++++-- mm/vmalloc.c | 7 - 4 files changed, 98 insertions(+), 10 deletions(-) diff -puN Documentation/dev-tools/kmemleak.rst~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects Documentation/dev-tools/kmemleak.rst --- a/Documentation/dev-tools/kmemleak.rst~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects +++ a/Documentation/dev-tools/kmemleak.rst @@ -150,6 +150,7 @@ See the include/linux/kmemleak.h header - ``kmemleak_init`` - initialize kmemleak - ``kmemleak_alloc`` - notify of a memory block allocation - ``kmemleak_alloc_percpu`` - notify of a percpu memory block allocation +- ``kmemleak_vmalloc`` - notify of a vmalloc() memory allocation - ``kmemleak_free`` - notify of a memory block freeing - ``kmemleak_free_part`` - notify of a partial memory block freeing - ``kmemleak_free_percpu`` - notify of a percpu memory block freeing diff -puN include/linux/kmemleak.h~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects include/linux/kmemleak.h --- a/include/linux/kmemleak.h~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects +++ a/include/linux/kmemleak.h @@ -22,6 +22,7 @@ #define __KMEMLEAK_H #include <linux/slab.h> +#include <linux/vmalloc.h> #ifdef CONFIG_DEBUG_KMEMLEAK @@ -30,6 +31,8 @@ extern void kmemleak_alloc(const void *p gfp_t gfp) __ref; extern void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size, gfp_t gfp) __ref; +extern void kmemleak_vmalloc(const struct vm_struct *area, size_t size, + gfp_t gfp) __ref; extern void kmemleak_free(const void *ptr) __ref; extern void kmemleak_free_part(const void *ptr, size_t size) __ref; extern void kmemleak_free_percpu(const void __percpu *ptr) __ref; @@ -81,6 +84,10 @@ static inline void kmemleak_alloc_percpu gfp_t gfp) { } +static inline void kmemleak_vmalloc(const struct vm_struct *area, size_t size, + gfp_t gfp) +{ +} static inline void kmemleak_free(const void *ptr) { } diff -puN mm/kmemleak.c~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects mm/kmemleak.c --- a/mm/kmemleak.c~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects +++ a/mm/kmemleak.c @@ -159,6 +159,8 @@ struct kmemleak_object { atomic_t use_count; unsigned long pointer; size_t size; + /* pass surplus references to this pointer */ + unsigned long excess_ref; /* minimum number of a pointers found before it is considered leak */ int min_count; /* the total number of pointers found pointing to this object */ @@ -253,7 +255,8 @@ enum { KMEMLEAK_NOT_LEAK, KMEMLEAK_IGNORE, KMEMLEAK_SCAN_AREA, - KMEMLEAK_NO_SCAN + KMEMLEAK_NO_SCAN, + KMEMLEAK_SET_EXCESS_REF }; /* @@ -264,7 +267,10 @@ struct early_log { int op_type; /* kmemleak operation type */ int min_count; /* minimum reference count */ const void *ptr; /* allocated/freed memory block */ - size_t size; /* memory block size */ + union { + size_t size; /* memory block size */ + unsigned long excess_ref; /* surplus reference passing */ + }; unsigned long trace[MAX_TRACE]; /* stack trace */ unsigned int trace_len; /* stack trace length */ }; @@ -562,6 +568,7 @@ static struct kmemleak_object *create_ob object->flags = OBJECT_ALLOCATED; object->pointer = ptr; object->size = size; + object->excess_ref = 0; object->min_count = min_count; object->count = 0; /* white color initially */ object->jiffies = jiffies; @@ -795,6 +802,30 @@ out: } /* + * Any surplus references (object already gray) to 'ptr' are passed to + * 'excess_ref'. This is used in the vmalloc() case where a pointer to + * vm_struct may be used as an alternative reference to the vmalloc'ed object + * (see free_thread_stack()). + */ +static void object_set_excess_ref(unsigned long ptr, unsigned long excess_ref) +{ + unsigned long flags; + struct kmemleak_object *object; + + object = find_and_get_object(ptr, 0); + if (!object) { + kmemleak_warn("Setting excess_ref on unknown object at 0x%08lx\n", + ptr); + return; + } + + spin_lock_irqsave(&object->lock, flags); + object->excess_ref = excess_ref; + spin_unlock_irqrestore(&object->lock, flags); + put_object(object); +} + +/* * Set the OBJECT_NO_SCAN flag for the object corresponding to the give * pointer. Such object will not be scanned by kmemleak but references to it * are searched. @@ -908,7 +939,7 @@ static void early_alloc_percpu(struct ea * @gfp: kmalloc() flags used for kmemleak internal memory allocations * * This function is called from the kernel allocators when a new object - * (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.). + * (memory block) is allocated (kmem_cache_alloc, kmalloc etc.). */ void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count, gfp_t gfp) @@ -952,6 +983,36 @@ void __ref kmemleak_alloc_percpu(const v EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu); /** + * kmemleak_vmalloc - register a newly vmalloc'ed object + * @area: pointer to vm_struct + * @size: size of the object + * @gfp: __vmalloc() flags used for kmemleak internal memory allocations + * + * This function is called from the vmalloc() kernel allocator when a new + * object (memory block) is allocated. + */ +void __ref kmemleak_vmalloc(const struct vm_struct *area, size_t size, gfp_t gfp) +{ + pr_debug("%s(0x%p, %zu)\n", __func__, area, size); + + /* + * A min_count = 2 is needed because vm_struct contains a reference to + * the virtual address of the vmalloc'ed block. + */ + if (kmemleak_enabled) { + create_object((unsigned long)area->addr, size, 2, gfp); + object_set_excess_ref((unsigned long)area, + (unsigned long)area->addr); + } else if (kmemleak_early_log) { + log_early(KMEMLEAK_ALLOC, area->addr, size, 2); + /* reusing early_log.size for storing area->addr */ + log_early(KMEMLEAK_SET_EXCESS_REF, + area, (unsigned long)area->addr, 0); + } +} +EXPORT_SYMBOL_GPL(kmemleak_vmalloc); + +/** * kmemleak_free - unregister a previously registered object * @ptr: pointer to beginning of the object * @@ -1248,6 +1309,7 @@ static void scan_block(void *_start, voi for (ptr = start; ptr < end; ptr++) { struct kmemleak_object *object; unsigned long pointer; + unsigned long excess_ref; if (scan_should_stop()) break; @@ -1283,8 +1345,27 @@ static void scan_block(void *_start, voi * enclosed by scan_mutex. */ spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING); - update_refs(object); + /* only pass surplus references (object already gray) */ + if (color_gray(object)) { + excess_ref = object->excess_ref; + /* no need for update_refs() if object already gray */ + } else { + excess_ref = 0; + update_refs(object); + } spin_unlock(&object->lock); + + if (excess_ref) { + object = lookup_object(excess_ref, 0); + if (!object) + continue; + if (object == scanned) + /* circular reference, ignore */ + continue; + spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING); + update_refs(object); + spin_unlock(&object->lock); + } } read_unlock_irqrestore(&kmemleak_lock, flags); } @@ -1987,6 +2068,10 @@ void __init kmemleak_init(void) case KMEMLEAK_NO_SCAN: kmemleak_no_scan(log->ptr); break; + case KMEMLEAK_SET_EXCESS_REF: + object_set_excess_ref((unsigned long)log->ptr, + log->excess_ref); + break; default: kmemleak_warn("Unknown early log operation: %d\n", log->op_type); diff -puN mm/vmalloc.c~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects mm/vmalloc.c --- a/mm/vmalloc.c~mm-kmemleak-treat-vm_struct-as-alternative-reference-to-vmalloced-objects +++ a/mm/vmalloc.c @@ -1770,12 +1770,7 @@ void *__vmalloc_node_range(unsigned long */ clear_vm_uninitialized_flag(area); - /* - * A ref_count = 2 is needed because vm_struct allocated in - * __get_vm_area_node() contains a reference to the virtual address of - * the vmalloc'ed block. - */ - kmemleak_alloc(addr, real_size, 2, gfp_mask); + kmemleak_vmalloc(area, size, gfp_mask); return addr; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
