diff options
| author | Catalin Marinas | 2015-06-24 16:58:26 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2015-06-24 17:49:45 -0700 |
| commit | c5f3b1a51a591c18c8b33983908e7fdda6ae417e (patch) | |
| tree | 0d09a41d69729eccedba223f9b9f4db36c88768b /mm/kmemleak.c | |
| parent | c2b42d3cadbffbf5117ccdbcb3a2fc47c0d59bae (diff) | |
mm: kmemleak: allow safe memory scanning during kmemleak disabling
The kmemleak scanning thread can run for minutes. Callbacks like
kmemleak_free() are allowed during this time, the race being taken care
of by the object->lock spinlock. Such lock also prevents a memory block
from being freed or unmapped while it is being scanned by blocking the
kmemleak_free() -> ... -> __delete_object() function until the lock is
released in scan_object().
When a kmemleak error occurs (e.g. it fails to allocate its metadata),
kmemleak_enabled is set and __delete_object() is no longer called on
freed objects. If kmemleak_scan is running at the same time,
kmemleak_free() no longer waits for the object scanning to complete,
allowing the corresponding memory block to be freed or unmapped (in the
case of vfree()). This leads to kmemleak_scan potentially triggering a
page fault.
This patch separates the kmemleak_free() enabling/disabling from the
overall kmemleak_enabled nob so that we can defer the disabling of the
object freeing tracking until the scanning thread completed. The
kmemleak_free_part() is deliberately ignored by this patch since this is
only called during boot before the scanning thread started.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>
Tested-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/kmemleak.c')
| -rw-r--r-- | mm/kmemleak.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/mm/kmemleak.c b/mm/kmemleak.c index f0fe4f2c1fa7..41df5b8efd25 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -195,6 +195,8 @@ static struct kmem_cache *scan_area_cache; /* set if tracing memory operations is enabled */ static int kmemleak_enabled; +/* same as above but only for the kmemleak_free() callback */ +static int kmemleak_free_enabled; /* set in the late_initcall if there were no errors */ static int kmemleak_initialized; /* enables or disables early logging of the memory operations */ @@ -942,7 +944,7 @@ void __ref kmemleak_free(const void *ptr) { pr_debug("%s(0x%p)\n", __func__, ptr); - if (kmemleak_enabled && ptr && !IS_ERR(ptr)) + if (kmemleak_free_enabled && ptr && !IS_ERR(ptr)) delete_object_full((unsigned long)ptr); else if (kmemleak_early_log) log_early(KMEMLEAK_FREE, ptr, 0, 0); @@ -982,7 +984,7 @@ void __ref kmemleak_free_percpu(const void __percpu *ptr) pr_debug("%s(0x%p)\n", __func__, ptr); - if (kmemleak_enabled && ptr && !IS_ERR(ptr)) + if (kmemleak_free_enabled && ptr && !IS_ERR(ptr)) for_each_possible_cpu(cpu) delete_object_full((unsigned long)per_cpu_ptr(ptr, cpu)); @@ -1750,6 +1752,13 @@ static void kmemleak_do_cleanup(struct work_struct *work) mutex_lock(&scan_mutex); stop_scan_thread(); + /* + * Once the scan thread has stopped, it is safe to no longer track + * object freeing. Ordering of the scan thread stopping and the memory + * accesses below is guaranteed by the kthread_stop() function. + */ + kmemleak_free_enabled = 0; + if (!kmemleak_found_leaks) __kmemleak_do_cleanup(); else @@ -1776,6 +1785,8 @@ static void kmemleak_disable(void) /* check whether it is too early for a kernel thread */ if (kmemleak_initialized) schedule_work(&cleanup_work); + else + kmemleak_free_enabled = 0; pr_info("Kernel memory leak detector disabled\n"); } @@ -1840,8 +1851,10 @@ void __init kmemleak_init(void) if (kmemleak_error) { local_irq_restore(flags); return; - } else + } else { kmemleak_enabled = 1; + kmemleak_free_enabled = 1; + } local_irq_restore(flags); /* |