Re: fuzz tested user mode linux crashed in NFS code path

[Kinglong Mee <kinglongmee@gmail.com>]

I think it is caused by kfree an uninitialized address.
Can you test with the patch listed in following url,
I have send some days before ?

"[PATCH 1/4] NFSD: Fix memory leak in encoding denied lock"
http://www.spinics.net/lists/linux-nfs/msg44719.html

thanks,
Kinglong Mee

On 7/12/2014 18:32, Toralf Förster wrote:
> A fuzz-tested a x86 32 bit user user mode linux guest using guest kernel v3.16-rc4-142-g47ea8dd 
> with trinity using NFSv4 victim files (both NFS server and NFS client run within the same UML).
> 
> The guest crashed :
> 
> Kernel panic - not syncing: BUG!
> CPU: 0 PID: 1395 Comm: nfsd Tainted: G    B         3.16.0-rc4-00142-g47ea8dd-dirty #68
> Stack:
>  0859f770 0859f770 00000003 086c8547 00000000 858742a0 0cacd700 85447e1c
>  084e3dd2 00000000 85447df0 85447e44 084e0408 085ab1c4 08700980 0859c46a
>  85447e50 00000000 00000000 858742a0 0cacd700 85447e74 080ffc70 0859c46a
> Call Trace:
>  [<084e3dd2>] dump_stack+0x26/0x28
>  [<084e0408>] panic+0x7a/0x194
>  [<080ffc70>] kfree+0x80/0x150
>  [<0822ba2e>] ? nfsd4_encode_stateid+0x3e/0x60
>  [<0822c0ab>] nfsd4_encode_lock+0x4b/0x60
>  [<08233aa3>] nfsd4_encode_operation+0xd3/0x1d0
>  [<0822afcf>] nfsd4_proc_compound+0x4bf/0x670
>  [<0809b999>] ? groups_alloc+0x39/0xe0
>  [<08219aba>] nfsd_dispatch+0xda/0x200
>  [<0846868f>] svc_process_common+0x31f/0x610
>  [<08469b4b>] svc_process+0x10b/0x140
>  [<0809d270>] ? default_wake_function+0x0/0x20
>  [<08219360>] ? nfsd+0x0/0x140
>  [<08219442>] nfsd+0xe2/0x140
>  [<08095806>] kthread+0xd6/0xe0
>  [<0809c60d>] ? finish_task_switch.isra.56+0x1d/0x70
>  [<0805f64b>] new_thread_handler+0x6b/0x90
> 
> 
> FWIW "dirty" cames from 1 patch from Richard Weinberger for arch/um/kernel/tlb.c and arch/um/os-Linux/skas/process.c
> 
> 
> The back trace of the core file gives:
> 
> 
> Thread 1 (LWP 12687):
> #0  0xb7797aec in __kernel_vsyscall ()
> #1  0x08484e15 in kill () at ../sysdeps/unix/syscall-template.S:81
> #2  0x0807253d in uml_abort () at arch/um/os-Linux/util.c:93
> #3  0x08072885 in os_dump_core () at arch/um/os-Linux/util.c:148
> #4  0x0806241d in panic_exit (self=0x86c95c0 <panic_exit_notifier>, unused1=0, unused2=0x8700980 <buf.19753>) at arch/um/kernel/um_arch.c:240
> #5  0x08099706 in notifier_call_chain (nl=0x0, val=2235858240, v=0x6, nr_to_call=-2, nr_calls=0x0) at kernel/notifier.c:93
> #6  0x08099863 in __atomic_notifier_call_chain (nr_calls=<optimized out>, nr_to_call=<optimized out>, v=<optimized out>, val=<optimized out>, nh=<optimized out>) at kernel/notifier.c:183
> #7  atomic_notifier_call_chain (nh=0x8700944 <panic_notifier_list>, val=0, v=0x8700980 <buf.19753>) at kernel/notifier.c:193
> #8  0x084e0424 in panic (fmt=0x0) at kernel/panic.c:133
> #9  0x080ffc70 in kfree (x=0x194) at mm/slub.c:3380
> #10 0x0822c0ab in nfsd4_encode_lock (resp=0x85871030, nfserr=0, lock=0x858742a0) at fs/nfsd/nfs4xdr.c:2910
> #11 0x08233aa3 in nfsd4_encode_operation (resp=0x85871030, op=0x85874280) at fs/nfsd/nfs4xdr.c:3889
> #12 0x0822afcf in nfsd4_proc_compound (rqstp=0x858750f0, args=0x85447d40, resp=0x85871030) at fs/nfsd/nfs4proc.c:1386
> #13 0x08219aba in nfsd_dispatch (rqstp=0x858750f0, statp=0x832c1018) at fs/nfsd/nfssvc.c:686
> #14 0x0846868f in svc_process_common (rqstp=0x858750f0, argv=0x85447d40, resv=0x8587526c) at net/sunrpc/svc.c:1206
> #15 0x08469b4b in svc_process (rqstp=0x858750f0) at net/sunrpc/svc.c:1331
> #16 0x08219442 in nfsd (vrqstp=0x858750f0) at fs/nfsd/nfssvc.c:609
> #17 0x08095806 in kthread (_create=0x85377eb0) at kernel/kthread.c:207
> #18 0x0805f64b in new_thread_handler () at arch/um/kernel/process.c:129
> #19 0x00000000 in ?? ()
> 
> 
>