kmemleak: Don't scan uninitialized memory when kmemcheck is enabled

Ingo Molnar reported the following kmemcheck warning when running both kmemleak and kmemcheck enabled: PM: Adding info for No Bus:vcsa7 WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (f6f6e1a4) d873f9f600000000c42ae4c1005c87f70000000070665f666978656400000000 i i i i u u u u i i i i i i i i i i i i i i i i i i i i i u u u ^ Pid: 3091, comm: kmemleak Not tainted (2.6.31-rc7-tip #1303) P4DC6 EIP: 0060:[<c110301f>] EFLAGS: 00010006 CPU: 0 EIP is at scan_block+0x3f/0xe0 EAX: f40bd700 EBX: f40bd780 ECX: f16b46c0 EDX: 00000001 ESI: f6f6e1a4 EDI: 00000000 EBP: f10f3f4c ESP: c2605fcc DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 CR0: 8005003b CR2: e89a4844 CR3: 30ff1000 CR4: 000006f0 DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 DR6: ffff4ff0 DR7: 00000400 [<c110313c>] scan_object+0x7c/0xf0 [<c1103389>] kmemleak_scan+0x1d9/0x400 [<c1103a3c>] kmemleak_scan_thread+0x4c/0xb0 [<c10819d4>] kthread+0x74/0x80 [<c10257db>] kernel_thread_helper+0x7/0x3c [<ffffffff>] 0xffffffff kmemleak: 515 new suspected memory leaks (see /sys/kernel/debug/kmemleak) kmemleak: 42 new suspected memory leaks (see /sys/kernel/debug/kmemleak) The problem here is that kmemleak will scan partially initialized objects that makes kmemcheck complain. Fix that up by skipping uninitialized memory regions when kmemcheck is enabled. Reported-by: Ingo Molnar <[email protected]> Acked-by: Ingo Molnar <[email protected]> Acked-by: Catalin Marinas <[email protected]> Signed-off-by: Pekka Enberg <[email protected]>
chewitt · Sep 4, 2009 · 8e01936 · 8e01936
1 parent acde31d
commit 8e01936
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Showing 3 changed files with 31 additions and 2 deletions.
diff --git a/arch/x86/mm/kmemcheck/kmemcheck.c b/arch/x86/mm/kmemcheck/kmemcheck.c
@@ -331,6 +331,20 @@ static void kmemcheck_read_strict(struct pt_regs *regs,
 	kmemcheck_shadow_set(shadow, size);
 }
 
+bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size)
+{
+	enum kmemcheck_shadow status;
+	void *shadow;
+
+	shadow = kmemcheck_shadow_lookup(addr);
+	if (!shadow)
+		return true;
+
+	status = kmemcheck_shadow_test(shadow, size);
+
+	return status == KMEMCHECK_SHADOW_INITIALIZED;
+}
+
 /* Access may cross page boundary */
 static void kmemcheck_read(struct pt_regs *regs,
 	unsigned long addr, unsigned int size)

diff --git a/include/linux/kmemcheck.h b/include/linux/kmemcheck.h
@@ -34,6 +34,8 @@ void kmemcheck_mark_initialized_pages(struct page *p, unsigned int n);
 int kmemcheck_show_addr(unsigned long address);
 int kmemcheck_hide_addr(unsigned long address);
 
+bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size);
+
 #else
 #define kmemcheck_enabled 0
 
@@ -99,6 +101,11 @@ static inline void kmemcheck_mark_initialized_pages(struct page *p,
 {
 }
 
+static inline bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size)
+{
+	return true;
+}
+
 #endif /* CONFIG_KMEMCHECK */
 
 /*

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
@@ -97,6 +97,7 @@
 #include <asm/processor.h>
 #include <asm/atomic.h>
 
+#include <linux/kmemcheck.h>
 #include <linux/kmemleak.h>
 
 /*
@@ -967,15 +968,22 @@ static void scan_block(void *_start, void *_end,
 	unsigned long *end = _end - (BYTES_PER_POINTER - 1);
 
 	for (ptr = start; ptr < end; ptr++) {
-		unsigned long flags;
-		unsigned long pointer = *ptr;
 		struct kmemleak_object *object;
+		unsigned long flags;
+		unsigned long pointer;
 
 		if (allow_resched)
 			cond_resched();
 		if (scan_should_stop())
 			break;
 
+		/* don't scan uninitialized memory */
+		if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
+						  BYTES_PER_POINTER))
+			continue;
+
+		pointer = *ptr;
+
 		object = find_and_get_object(pointer, 1);
 		if (!object)
 			continue;