Re: [PATCH] kmemleak: Increase maximum early log entries to 1000000

[Dmitry Vyukov]

On Tue, Jul 23, 2019 at 10:13 AM Nicolas Boichat <drinkcat@xxxxxxxxxxxx> wrote:
>
> On Tue, Jul 23, 2019 at 3:46 PM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> >
> > On Tue, Jul 23, 2019 at 9:26 AM Nicolas Boichat <drinkcat@xxxxxxxxxxxx> wrote:
> > >
> > > When KASan is enabled, a lot of memory is allocated early on,
> > > and kmemleak complains (this is on a 4GB RAM system):
> > > kmemleak: Early log buffer exceeded (129846), please increase
> > >   DEBUG_KMEMLEAK_EARLY_LOG_SIZE
> > >
> > > Let's increase the upper limit to 1M entry. That would take up
> > > 160MB of RAM at init (each early_log entry is 160 bytes), but
> > > the memory would later be freed (early_log is __initdata).
> >
> > Interesting. Is it on an arm64 system?
>
> Yes arm64. And this is chromiumos-4.19 tree. I didn't try to track
> down where these allocations come from...

So perhaps it's due to arm64, or you have even more configs, or maybe
running on real hardware. But I guess it's fine as is, just wondered
why such a radical difference. Thanks.

> Slightly redacted dmesg until the error message:
> [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd034]
> [    0.000000] Linux version 4.19.59 (drinkcat@X) (Chromium OS
> 9.0_pre361749_p20190714-r2 clang version 9.0.0
> (/var/cache/chromeos-cache/distfiles/host/egit-src/llvm-project
> c11de5eada2decd0a495ea02676b6f4838cd54fb) (based on LLVM 9.0.0svn)) #7
> SMP PREEMPT Tue Jul 23 16:00:50 CST 2019
> [    0.000000] Machine model: XYZ
> [    0.000000] Malformed early option 'console'
> [    0.000000] Reserved memory: created DMA memory pool at
> 0x0000000050000000, size 41 MiB
> [    0.000000] OF: reserved mem: initialized node scp_mem_region,
> compatible id shared-dma-pool
> [    0.000000] On node 0 totalpages: 1031920
> [    0.000000]   DMA32 zone: 12288 pages used for memmap
> [    0.000000]   DMA32 zone: 0 pages reserved
> [    0.000000]   DMA32 zone: 769776 pages, LIFO batch:63
> [    0.000000]   Normal zone: 4096 pages used for memmap
> [    0.000000]   Normal zone: 262144 pages, LIFO batch:63
> [    0.000000] kmemleak: Kernel memory leak detector disabled
> [    0.000000] kasan: KernelAddressSanitizer initialized
> [    0.000000] psci: probing for conduit method from DT.
> [    0.000000] psci: PSCIv1.1 detected in firmware.
> [    0.000000] psci: Using standard PSCI v0.2 function IDs
> [    0.000000] psci: MIGRATE_INFO_TYPE not supported.
> [    0.000000] psci: SMC Calling Convention v1.1
> [    0.000000] random: get_random_bytes called from
> start_kernel+0x8c/0x384 with crng_init=0
> [    0.000000] percpu: Embedded 32 pages/cpu s92904 r8192 d29976 u131072
> [    0.000000] pcpu-alloc: s92904 r8192 d29976 u131072 alloc=32*4096
> [    0.000000] pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3 [0] 4 [0] 5 [0] 6 [0] 7
> [    0.000000] Detected VIPT I-cache on CPU0
> [    0.000000] CPU features: enabling workaround for ARM erratum 845719
> [    0.000000] Speculative Store Bypass Disable mitigation not required
> [    0.000000] CPU features: detected: Kernel page table isolation (KPTI)
> [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 1015536
> [    0.000000] Kernel command line: cros_secure cros_secure console=
> loglevel=7 init=/sbin/init cros_secure
> root=PARTUUID=45e54c6a-06a8-374c-a934-a07e23b37225/PARTNROFF=1
> rootwait rw dm_verity.error_behavior=3 dm_verity.max_bios=-1
> dm_verity.dev_wait=0 dm="1 vroot none ro 1,0 4710400 verity
> payload=ROOT_DEV hashtree=HASH_DEV hashstart=4710400 alg=sha256
> root_hexdigest=443fe95947f3b3f3cb54a10a53a4c7bb600ea1dd26d002066821236efa2419f4
> salt=ba17ba7736672036f119b0c925aa43e10ae1a960591a5b8bc85b21c166a49132"
> noinitrd cros_debug vt.global_cursor_default=0
> kern_guid=45e54c6a-06a8-374c-a934-a07e23b37225
> [    0.000000] device-mapper: init: will configure 1 devices
> [    0.000000] Dentry cache hash table entries: 524288 (order: 10,
> 4194304 bytes)
> [    0.000000] Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
> [    0.000000] software IO TLB: mapped [mem 0xfbdff000-0xffdff000] (64MB)
> [    0.000000] Memory: 3439892K/4127680K available (9726K kernel code,
> 1106K rwdata, 3064K rodata, 4096K init, 8893K bss, 687788K reserved,
> 0K cma-reserved)
> [    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=8, Nodes=1
> [    0.000000] ftrace: allocating 34965 entries in 137 pages
> [    0.000000] rcu: Preemptible hierarchical RCU implementation.
> [    0.000000]  Tasks RCU enabled.
> [    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
> [    0.000000] GICv3: GIC: Using split EOI/Deactivate mode
> [    0.000000] GICv3: Distributor has no Range Selector support
> [    0.000000] GICv3: no VLPI support, no direct LPI support
> [    0.000000] GICv3: CPU0: found redistributor 0 region 0:0x000000000c100000
> [    0.000000] GICv3: GIC: PPI partition interrupt-partition-0[0] {
> /cpus/cpu@0[0] /cpus/cpu@1[1] /cpus/cpu@2[2] /cpus/cpu@3[3] }
> [    0.000000] GICv3: GIC: PPI partition interrupt-partition-1[1] {
> /cpus/cpu@100[4] /cpus/cpu@101[5] /cpus/cpu@102[6] /cpus/cpu@103[7] }
> [    0.000000] arch_timer: cp15 timer(s) running at 13.00MHz (phys).
> [    0.000000] clocksource: arch_sys_counter: mask: 0xffffffffffffff
> max_cycles: 0x2ff89eacb, max_idle_ns: 440795202429 ns
> [    0.000003] sched_clock: 56 bits at 13MHz, resolution 76ns, wraps
> every 4398046511101ns
> [    0.000441] kmemleak: Early log buffer exceeded (131217), please
> increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE
>
> > On syzbot we use 16000 and it's
> > enough for a very beefy config:
> >
> > https://github.com/google/syzkaller/blob/master/dashboard/config/upstream-leak.config
> >
> > If it's freed later, I would increase the default as well.
>
> Sure I can do that as part of a v2, at least to 16K, maybe more if we
> have no reason to believe there is another issue with my
> configuration.

That would be nice. I am all for tools working out of the box and
currently KMEMLEAK always fails in obscure mode.
Though I understand I am piggy-backing on your formally unrelated change ;)


> > 400 never
> > worked for me and I've seen people being confused and wasn't able to
> > use kmemleak, e.g.:
> >
> > https://groups.google.com/forum/#!searchin/syzkaller/CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE|sort:date/syzkaller/Rzf2ZRC9Qxw/tLog4DHXAgAJ
> >
> > https://groups.google.com/forum/#!searchin/syzkaller/CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE|sort:date/syzkaller/5HxmTuQ7U4A/XM8s2o2CCAAJ
> >
> >
> >
> > > Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
> > > ---
> > >  lib/Kconfig.debug | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > > index f567875b87657de..1a197b8125768b9 100644
> > > --- a/lib/Kconfig.debug
> > > +++ b/lib/Kconfig.debug
> > > @@ -595,7 +595,7 @@ config DEBUG_KMEMLEAK
> > >  config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
> > >         int "Maximum kmemleak early log entries"
> > >         depends on DEBUG_KMEMLEAK
> > > -       range 200 40000
> > > +       range 200 1000000
> > >         default 400
> > >         help
> > >           Kmemleak must track all the memory allocations to avoid
> > > --
> > > 2.22.0.657.g960e92d24f-goog
> > >