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: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
mm/kmemleak.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index f0fe4f2c1fa7..11d6f8015896 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 +1752,12 @@ 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.
+ */
+ 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);
/*
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>