diff options
author | Catalin Marinas <catalin.marinas@arm.com> | 2015-06-19 09:01:28 +1000 |
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committer | Gerrit - the friendly Code Review server <code-review@localhost> | 2015-06-25 21:39:11 -0700 |
commit | 631691fe401bb6f8bbe060d6f2ccc6fc2b2e9b71 (patch) | |
tree | bcdce4cea531a9b5c62f32ff216979b43b1901e4 | |
parent | ef0a3828c5039a4178f54ad0c2780abc11048b23 (diff) | |
download | qcom-631691fe401bb6f8bbe060d6f2ccc6fc2b2e9b71.tar.gz |
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.
Change-Id: Idec67be116b23ee9aa56419e8f7c9e17df0086f2
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>
Git-commit: d613b66e1df80fddfff8e3eaa704243a955158db
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
Signed-off-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>
-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 6057406abd9..280febc09b6 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -193,6 +193,8 @@ 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 */ @@ -950,7 +952,7 @@ 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); @@ -990,7 +992,7 @@ 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)); @@ -1724,6 +1726,13 @@ 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 @@ -1750,6 +1759,8 @@ 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"); } @@ -1814,8 +1825,10 @@ 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); /* |