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Re: audit-related slab memory leak in recent -mm kernels?



On Fri, Feb 24, 2006 at 01:41:24PM -0500, Valdis Kletnieks vt edu wrote:
> For a while, I've been seeing a pretty serious leak in slab-32 entries in -mm
> kernels. Doing a quilt bisection on -mm calls out git-audit.patch as the
> offender.
> 
> In kernel/auditsc.c, we have audit_inode_context(), which does:
> 
>         ctx = kmalloc(len, GFP_KERNEL);
> 	...
>         context->names[idx].ctx = ctx;
> 
> but the only obvious kfree() I can find is in audit_free_names(), but that
> one is (a) inside an if statement along with a printk(KERN_ERR) and (b) has
> a '#if AUDIT_DEBUG == 2' around it.
> 
> [/usr/src/linux-2.6.16-rc4-mm2/kernel]1 grep -n '\.ctx' *.c
> auditsc.c:384:                  kfree(context->names[i].ctx);
> auditsc.c:686:          if (context->names[i].ctx) {
> auditsc.c:688:                                  context->names[i].ctx);
> auditsc.c:961:  context->names[idx].ctx = ctx;
> 
> Is this my memory leak?  If so, who is supposed to be freeing it?

That kfree is misplaced.  It should be here.  Does this solve it on
your end?

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 4626c35..1867fc3 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -381,7 +381,6 @@ static inline void audit_free_names(stru
 			printk(KERN_ERR "names[%d] = %p = %s\n", i,
 			       context->names[i].name,
 			       context->names[i].name ?: "(null)");
-			kfree(context->names[i].ctx);
 		}
 		dump_stack();
 		return;
@@ -392,9 +391,11 @@ static inline void audit_free_names(stru
 	context->ino_count  = 0;
 #endif
 
-	for (i = 0; i < context->name_count; i++)
+	for (i = 0; i < context->name_count; i++) {
 		if (context->names[i].name)
 			__putname(context->names[i].name);
+		kfree(context->names[i].ctx);
+	}
 	context->name_count = 0;
 	if (context->pwd)
 		dput(context->pwd);


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