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kmemleak: enable tracking for percpu pointers

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Patch series "kmemleak: support for percpu memory leak detect'.

This is a rework of this series:
https://lore.kernel.org/lkml/20200921020007.35803-1-chenjun102@huawei.com/

Originally I was investigating a percpu leak on our customer nodes and
having this functionality was a huge help, which lead to this fix [1].

So probably it's a good idea to have it in mainstream too, especially as
after [2] it became much easier to implement (we already have a separate
tree for percpu pointers).

[1] commit 0af8c09c89 ("netfilter: x_tables: fix percpu counter block leak on error path when creating new netns")
[2] commit 39042079a0 ("kmemleak: avoid RCU stalls when freeing metadata for per-CPU pointers")


This patch (of 2):

This basically does:

- Add min_percpu_addr and max_percpu_addr to filter out unrelated data
  similar to min_addr and max_addr;

- Set min_count for percpu pointers to 1 to start tracking them;

- Calculate checksum of percpu area as xor of crc32 for each cpu;

- Split pointer lookup and update refs code into separate helper and use
  it twice: once as if the pointer is a virtual pointer and once as if
  it's percpu.

[ptikhomirov@virtuozzo.com: v2]
  Link: https://lkml.kernel.org/r/20240731025526.157529-2-ptikhomirov@virtuozzo.com
Link: https://lkml.kernel.org/r/20240725041223.872472-1-ptikhomirov@virtuozzo.com
Link: https://lkml.kernel.org/r/20240725041223.872472-2-ptikhomirov@virtuozzo.com
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Cc: Chen Jun <chenjun102@huawei.com>
Cc: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pavel Tikhomirov 2024-07-25 12:12:15 +08:00 committed by Andrew Morton
parent fbe76a6557
commit 6c99d4eb7c
1 changed files with 94 additions and 59 deletions
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153
mm/kmemleak.c
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@ -224,6 +224,10 @@ static int kmemleak_error;
static unsigned long min_addr = ULONG_MAX;
static unsigned long max_addr;
/* minimum and maximum address that may be valid per-CPU pointers */
static unsigned long min_percpu_addr = ULONG_MAX;
static unsigned long max_percpu_addr;
static struct task_struct *scan_thread;
/* used to avoid reporting of recently allocated objects */
static unsigned long jiffies_min_age;
@ -294,13 +298,20 @@ static void hex_dump_object(struct seq_file *seq,
const u8 *ptr = (const u8 *)object->pointer;
size_t len;
if (WARN_ON_ONCE(object->flags & (OBJECT_PHYS | OBJECT_PERCPU)))
if (WARN_ON_ONCE(object->flags & OBJECT_PHYS))
return;
if (object->flags & OBJECT_PERCPU)
ptr = (const u8 *)this_cpu_ptr((void __percpu *)object->pointer);
/* limit the number of lines to HEX_MAX_LINES */
len = min_t(size_t, object->size, HEX_MAX_LINES * HEX_ROW_SIZE);
warn_or_seq_printf(seq, " hex dump (first %zu bytes):\n", len);
if (object->flags & OBJECT_PERCPU)
warn_or_seq_printf(seq, " hex dump (first %zu bytes on cpu %d):\n",
len, raw_smp_processor_id());
else
warn_or_seq_printf(seq, " hex dump (first %zu bytes):\n", len);
kasan_disable_current();
warn_or_seq_hex_dump(seq, DUMP_PREFIX_NONE, HEX_ROW_SIZE,
HEX_GROUP_SIZE, kasan_reset_tag((void *)ptr), len, HEX_ASCII);
@ -695,10 +706,14 @@ static int __link_object(struct kmemleak_object *object, unsigned long ptr,
untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
/*
* Only update min_addr and max_addr with object
* storing virtual address.
* Only update min_addr and max_addr with object storing virtual
* address. And update min_percpu_addr max_percpu_addr for per-CPU
* objects.
*/
if (!(objflags & (OBJECT_PHYS | OBJECT_PERCPU))) {
if (objflags & OBJECT_PERCPU) {
min_percpu_addr = min(min_percpu_addr, untagged_ptr);
max_percpu_addr = max(max_percpu_addr, untagged_ptr + size);
} else if (!(objflags & OBJECT_PHYS)) {
min_addr = min(min_addr, untagged_ptr);
max_addr = max(max_addr, untagged_ptr + size);
}
@ -1055,12 +1070,8 @@ void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
{
pr_debug("%s(0x%px, %zu)\n", __func__, ptr, size);
/*
* Percpu allocations are only scanned and not reported as leaks
* (min_count is set to 0).
*/
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
create_object_percpu((unsigned long)ptr, size, 0, gfp);
create_object_percpu((unsigned long)ptr, size, 1, gfp);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
@ -1304,12 +1315,23 @@ static bool update_checksum(struct kmemleak_object *object)
{
u32 old_csum = object->checksum;
if (WARN_ON_ONCE(object->flags & (OBJECT_PHYS | OBJECT_PERCPU)))
if (WARN_ON_ONCE(object->flags & OBJECT_PHYS))
return false;
kasan_disable_current();
kcsan_disable_current();
object->checksum = crc32(0, kasan_reset_tag((void *)object->pointer), object->size);
if (object->flags & OBJECT_PERCPU) {
unsigned int cpu;
object->checksum = 0;
for_each_possible_cpu(cpu) {
void *ptr = per_cpu_ptr((void __percpu *)object->pointer, cpu);
object->checksum ^= crc32(0, kasan_reset_tag((void *)ptr), object->size);
}
} else {
object->checksum = crc32(0, kasan_reset_tag((void *)object->pointer), object->size);
}
kasan_enable_current();
kcsan_enable_current();
@ -1340,6 +1362,64 @@ static void update_refs(struct kmemleak_object *object)
}
}
static void pointer_update_refs(struct kmemleak_object *scanned,
unsigned long pointer, unsigned int objflags)
{
struct kmemleak_object *object;
unsigned long untagged_ptr;
unsigned long excess_ref;
untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer);
if (objflags & OBJECT_PERCPU) {
if (untagged_ptr < min_percpu_addr || untagged_ptr >= max_percpu_addr)
return;
} else {
if (untagged_ptr < min_addr || untagged_ptr >= max_addr)
return;
}
/*
* No need for get_object() here since we hold kmemleak_lock.
* object->use_count cannot be dropped to 0 while the object
* is still present in object_tree_root and object_list
* (with updates protected by kmemleak_lock).
*/
object = __lookup_object(pointer, 1, objflags);
if (!object)
return;
if (object == scanned)
/* self referenced, ignore */
return;
/*
* Avoid the lockdep recursive warning on object->lock being
* previously acquired in scan_object(). These locks are
* enclosed by scan_mutex.
*/
raw_spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
/* 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);
}
raw_spin_unlock(&object->lock);
if (excess_ref) {
object = lookup_object(excess_ref, 0);
if (!object)
return;
if (object == scanned)
/* circular reference, ignore */
return;
raw_spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
update_refs(object);
raw_spin_unlock(&object->lock);
}
}
/*
* Memory scanning is a long process and it needs to be interruptible. This
* function checks whether such interrupt condition occurred.
@ -1372,13 +1452,10 @@ static void scan_block(void *_start, void *_end,
unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
unsigned long *end = _end - (BYTES_PER_POINTER - 1);
unsigned long flags;
unsigned long untagged_ptr;
raw_spin_lock_irqsave(&kmemleak_lock, flags);
for (ptr = start; ptr < end; ptr++) {
struct kmemleak_object *object;
unsigned long pointer;
unsigned long excess_ref;
if (scan_should_stop())
break;
@ -1387,50 +1464,8 @@ static void scan_block(void *_start, void *_end,
pointer = *(unsigned long *)kasan_reset_tag((void *)ptr);
kasan_enable_current();
untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer);
if (untagged_ptr < min_addr || untagged_ptr >= max_addr)
continue;
/*
* No need for get_object() here since we hold kmemleak_lock.
* object->use_count cannot be dropped to 0 while the object
* is still present in object_tree_root and object_list
* (with updates protected by kmemleak_lock).
*/
object = lookup_object(pointer, 1);
if (!object)
continue;
if (object == scanned)
/* self referenced, ignore */
continue;
/*
* Avoid the lockdep recursive warning on object->lock being
* previously acquired in scan_object(). These locks are
* enclosed by scan_mutex.
*/
raw_spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
/* 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);
}
raw_spin_unlock(&object->lock);
if (excess_ref) {
object = lookup_object(excess_ref, 0);
if (!object)
continue;
if (object == scanned)
/* circular reference, ignore */
continue;
raw_spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
update_refs(object);
raw_spin_unlock(&object->lock);
}
pointer_update_refs(scanned, pointer, 0);
pointer_update_refs(scanned, pointer, OBJECT_PERCPU);
}
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
}