Messages in this thread | | | Date | Tue, 2 Jan 2024 20:07:52 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCH] don't record leak information on allocations done between kmemleak_init and kmemleak_late_init |
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On Tue, Jan 02, 2024 at 10:34:28AM -0500, Chris von Recklinghausen wrote: > If an object is allocated after kmemleak_init is called but before > kmemleak_late_init is called, calls to kmemleak_not_leak or > kmemleak_ignore on the object don't prevent a scan from reporting the > object as a leak.
This may be true but what is the reason for this? Can you give some example of false positives you get?
> Avoid this situation by only registering objects in kmemleak_alloc when > kmemleak_initialized is set.
I wouldn't do this, kmemleak needs to track all the early allocations, otherwise it will lead to lots of false positives. However, looking at your patch, it looks like it doesn't touch kmemleak_alloc() at all and it does something completely different.
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index 5501363d6b31..0c8a5f456874 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -1117,7 +1117,8 @@ void __ref kmemleak_free_part(const void *ptr, size_t size) > { > pr_debug("%s(0x%px)\n", __func__, ptr); > > - if (kmemleak_enabled && ptr && !IS_ERR(ptr)) > + if (kmemleak_enabled && kmemleak_late_initialized && ptr && > + !IS_ERR(ptr)) > delete_object_part((unsigned long)ptr, size, false); > }
This leaves some memory to still be tracked by kmemleak when it was actually freed. Later when it is reallocated, you'll get some errors and kmemleak will disable itself.
> EXPORT_SYMBOL_GPL(kmemleak_free_part); > @@ -1135,7 +1136,8 @@ void __ref kmemleak_free_percpu(const void __percpu *ptr) > > pr_debug("%s(0x%px)\n", __func__, ptr); > > - if (kmemleak_free_enabled && ptr && !IS_ERR(ptr)) > + if (kmemleak_free_enabled && kmemleak_late_initialized && ptr && > + !IS_ERR(ptr)) > for_each_possible_cpu(cpu) > delete_object_full((unsigned long)per_cpu_ptr(ptr, > cpu));
Same here.
> @@ -1189,7 +1191,8 @@ void __ref kmemleak_not_leak(const void *ptr) > { > pr_debug("%s(0x%px)\n", __func__, ptr); > > - if (kmemleak_enabled && ptr && !IS_ERR(ptr)) > + if (kmemleak_enabled && kmamleak_late_initialized && ptr && ^^^ I guess you haven't compiled this patch. Does it actually fix the problem you are reporting?
> + !IS_ERR(ptr)) > make_gray_object((unsigned long)ptr); > }
This change doesn't help at all with your problem statement.
> EXPORT_SYMBOL(kmemleak_not_leak); > @@ -1207,7 +1210,8 @@ void __ref kmemleak_ignore(const void *ptr) > { > pr_debug("%s(0x%px)\n", __func__, ptr); > > - if (kmemleak_enabled && ptr && !IS_ERR(ptr)) > + if (kmemleak_enabled && kmamleak_late_initialized && ptr && > + !IS_ERR(ptr)) > make_black_object((unsigned long)ptr, false); > } > EXPORT_SYMBOL(kmemleak_ignore);
Neither does this.
Also if you re-post, please cc linux-mm as well. Andrew Morton tends to pick up the kmemleak patches (once acked).
-- Catalin
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