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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Trond Myklebust <trondmy@hammerspace.com>
CC:     Bruce Fields <bfields@fieldses.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH] NFSD: Prevent a possible oops in the nfs_dirent()
 tracepoint
Thread-Topic: [PATCH] NFSD: Prevent a possible oops in the nfs_dirent()
 tracepoint
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Date:   Fri, 25 Jun 2021 18:05:12 +0000
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> On Jun 25, 2021, at 12:28 PM, Trond Myklebust <trondmy@hammerspace.com> w=
rote:
>=20
> On Fri, 2021-06-25 at 11:12 -0400, Chuck Lever wrote:
>> The double copy of the string is a mistake, plus __assign_str()
>> uses strlen(), which is wrong to do on a string that isn't
>> guaranteed to be NUL-terminated.
>>=20
>> Fixes: 6019ce0742ca ("NFSD: Add a tracepoint to record directory
>> entry encoding")
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---
>>  fs/nfsd/trace.h |    1 -
>>  1 file changed, 1 deletion(-)
>>=20
>> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
>> index 27a93ebd1d80..89dccced526a 100644
>> --- a/fs/nfsd/trace.h
>> +++ b/fs/nfsd/trace.h
>> @@ -408,7 +408,6 @@ TRACE_EVENT(nfsd_dirent,
>>                 __entry->ino =3D ino;
>>                 __entry->len =3D namlen;
>>                 memcpy(__get_str(name), name, namlen);
>> -               __assign_str(name, name);
>>         ),
>>         TP_printk("fh_hash=3D0x%08x ino=3D%llu name=3D%.*s",
>>                 __entry->fh_hash, __entry->ino,
>>=20
>>=20
>=20
> Why not just store it as a NUL terminated string and save a few bytes
> by getting rid of the integer-sized storage of the length?

Stephen is adding some helpers to do that in the next merge
window. For now, I need to fix this oops, and this is the
fastest way to do that.


--
Chuck Lever