Subject: [Bug 204371] BUG kmalloc-4k (Tainted: G W ): Object padding overwritten

From: [email-masked]
Date: Wed, 31 Jul 2019 09:03:45 +0000

https://bugzilla.kernel.org/show_bug.cgi?id=204371

--- Comment #3 from Erhard F. ([email-masked]) ---
On Tue, 30 Jul 2019 11:52:44 -0700
Andrew Morton <[email-masked]> wrote:

> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
> 
> 
> On Mon, 29 Jul 2019 22:35:48 +0000 [email-masked] wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=204371
> > 
> >             Bug ID: 204371
> >            Summary: BUG kmalloc-4k (Tainted: G        W        ): Object
> >                     padding overwritten
> >            Product: Memory Management
> >            Version: 2.5
> >     Kernel Version: 5.3.0-rc2
> >           Hardware: PPC-32
> >                 OS: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: Slab Allocator
> >           Assignee: [email-masked]
> >           Reporter: [email-masked]
> >         Regression: No  
> 
> cc'ing various people here.
> 
> I suspect proc_cgroup_show() is innocent and that perhaps
> bpf_prepare_filter() had a memory scribble.  iirc there has been at
> least one recent pretty serious bpf fix applied recently.  Can others
> please take a look?
> 
> (Seriously - please don't modify this report via the bugzilla web interface!)

Hm, don't know whether this is bpfs fault.. I am getting this for other things
too:

[...]
Jul 31 10:46:53 T600 kernel: Object 442ee539: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
Jul 31 10:46:53 T600 kernel: Object 41b83bb9: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
6b 6b 6b 6b a5  kkkkkkkkkkkkkkk.
Jul 31 10:46:53 T600 kernel: Redzone 720e193a: bb bb bb bb                     
                ....
Jul 31 10:46:53 T600 kernel: Padding 0b116c89: 00 00 00 00 00 00 00 00         
                ........
Jul 31 10:46:53 T600 kernel: CPU: 1 PID: 120 Comm: systemd-journal Tainted: G  
 B   W         5.2.4-gentoo #1
Jul 31 10:46:53 T600 kernel: Call Trace:
Jul 31 10:46:53 T600 kernel: [dd663b68] [c0628d80] dump_stack+0xa0/0xfc
(unreliable)
Jul 31 10:46:53 T600 kernel: [dd663b98] [c01984ac]
check_bytes_and_report+0xc8/0xf0
Jul 31 10:46:53 T600 kernel: [dd663bc8] [c0198fd0] check_object+0x10c/0x224
Jul 31 10:46:53 T600 kernel: [dd663bf8] [c0199964]
alloc_debug_processing+0xc4/0x13c
Jul 31 10:46:53 T600 kernel: [dd663c18] [c0199bc4]
___slab_alloc.constprop.72+0x1e8/0x380
Jul 31 10:46:53 T600 kernel: [dd663ca8] [c0199d9c]
__slab_alloc.constprop.71+0x40/0x6c
Jul 31 10:46:53 T600 kernel: [dd663cd8] [c019a014]
kmem_cache_alloc_trace+0x7c/0x170
Jul 31 10:46:53 T600 kernel: [dd663d18] [c02d6a5c] btrfs_opendir+0x48/0x78
Jul 31 10:46:53 T600 kernel: [dd663d38] [c01a9320] do_dentry_open+0x25c/0x2f0
Jul 31 10:46:53 T600 kernel: [dd663d68] [c01bc284] path_openat+0x814/0xaf0
Jul 31 10:46:53 T600 kernel: [dd663e38] [c01bc5a4] do_filp_open+0x44/0xa0
Jul 31 10:46:53 T600 kernel: [dd663ee8] [c01aa178] do_sys_open+0x7c/0x108
Jul 31 10:46:53 T600 kernel: [dd663f38] [c0015274] ret_from_syscall+0x0/0x34
Jul 31 10:46:53 T600 kernel: --- interrupt: c00 at 0x7eae14
                                 LR = 0x7eadf8
Jul 31 10:46:53 T600 kernel: FIX kmalloc-4k: Restoring
0x0b116c89-0x85f2eca1=0x5a
[...]

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