+ mm-kmemleak-fix-crashing-during-kmemleak-disabling.patch added to -mm tree

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The patch titled
     Subject: mm: kmemleak: fix crashing during kmemleak disabling
has been added to the -mm tree.  Its filename is
     mm-kmemleak-fix-crashing-during-kmemleak-disabling.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-kmemleak-fix-crashing-during-kmemleak-disabling.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-kmemleak-fix-crashing-during-kmemleak-disabling.patch

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------------------------------------------------------
From: Catalin Marinas <catalin.marinas@xxxxxxx>
Subject: mm: kmemleak: fix crashing during kmemleak disabling

With the current implementation, if kmemleak is disabled because of an
error condition (e.g.  fails to allocate metadata), alloc/free calls are
no longer tracked.  Usually this is not a problem since the kmemleak
metadata is being removed via kmemleak_do_cleanup().  However, if the
scanning thread is running at the time of disabling, kmemleak would no
longer notice a potential vfree() call and the freed/unmapped object may
still be accessed, causing a 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@xxxxxxx>
Reported-by: Vignesh Radhakrishnan <vigneshr@xxxxxxxxxxxxxx>
Tested-by: Vignesh Radhakrishnan <vigneshr@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/kmemleak.c |   18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff -puN mm/kmemleak.c~mm-kmemleak-fix-crashing-during-kmemleak-disabling mm/kmemleak.c
--- a/mm/kmemleak.c~mm-kmemleak-fix-crashing-during-kmemleak-disabling
+++ a/mm/kmemleak.c
@@ -195,6 +195,8 @@ static struct kmem_cache *scan_area_cach
 
 /* 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 vo
 
 	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 +1752,12 @@ static void kmemleak_do_cleanup(struct w
 	mutex_lock(&scan_mutex);
 	stop_scan_thread();
 
+	/*
+	 * Once the scan thread has stopped, it is safe to no longer track
+	 * object freeing.
+	 */
+	kmemleak_free_enabled = 0;
+
 	if (!kmemleak_found_leaks)
 		__kmemleak_do_cleanup();
 	else
@@ -1776,6 +1784,8 @@ 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 +1850,10 @@ 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);
 
 	/*
_

Patches currently in -mm which might be from catalin.marinas@xxxxxxx are

mm-kmemleak-fix-crashing-during-kmemleak-disabling.patch
mm-hugetlb-reduce-arch-dependent-code-about-huge_pmd_unshare.patch
linux-next.patch

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