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Message-ID: <DFAEDAE5-7A7C-459F-B0EA-02F938D9D2BD@oracle.com>
Date: Mon, 7 Nov 2022 14:07:07 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Dan Carpenter <error27@...il.com>
CC: "oe-kbuild@...ts.linux.dev" <oe-kbuild@...ts.linux.dev>,
Jeff Layton <jlayton@...nel.org>,
"lkp@...el.com" <lkp@...el.com>,
"oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: fs/nfsd/filecache.c:1118 nfsd_file_do_acquire() warn: passing
freed memory 'nf'
> On Nov 7, 2022, at 2:48 AM, Dan Carpenter <error27@...il.com> wrote:
>
> On Sat, Nov 05, 2022 at 03:39:59PM +0000, Chuck Lever III wrote:
>>
>>
>>> On Nov 5, 2022, at 7:17 AM, Dan Carpenter <error27@...il.com> wrote:
>>>
>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>>> head: b208b9fbbcba743fb269d15cb46a4036b01936b1
>>> commit: 243a5263014a30436c93ed3f1f864c1da845455e nfsd: rework hashtable handling in nfsd_do_file_acquire
>>> config: alpha-randconfig-m041-20221030
>>> compiler: alpha-linux-gcc (GCC) 12.1.0
>>>
>>> If you fix the issue, kindly add following tag where applicable
>>> | Reported-by: kernel test robot <lkp@...el.com>
>>> | Reported-by: Dan Carpenter <error27@...il.com>
>>>
>>> smatch warnings:
>>> fs/nfsd/filecache.c:1118 nfsd_file_do_acquire() warn: passing freed memory 'nf'
>>>
>>> vim +/nf +1118 fs/nfsd/filecache.c
>>>
>>> fb70bf124b051d Chuck Lever 2022-03-30 1036 static __be32
>>> be0230069fcbf7 Chuck Lever 2022-07-08 1037 nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
>>> fb70bf124b051d Chuck Lever 2022-03-30 1038 unsigned int may_flags, struct nfsd_file **pnf, bool open)
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1039 {
>>> ce502f81ba884c Chuck Lever 2022-07-08 1040 struct nfsd_file_lookup_key key = {
>>> ce502f81ba884c Chuck Lever 2022-07-08 1041 .type = NFSD_FILE_KEY_FULL,
>>> ce502f81ba884c Chuck Lever 2022-07-08 1042 .need = may_flags & NFSD_FILE_MAY_MASK,
>>> ce502f81ba884c Chuck Lever 2022-07-08 1043 .net = SVC_NET(rqstp),
>>> ce502f81ba884c Chuck Lever 2022-07-08 1044 };
>>> 243a5263014a30 Jeff Layton 2022-10-04 1045 bool open_retry = true;
>>> 243a5263014a30 Jeff Layton 2022-10-04 1046 struct nfsd_file *nf;
>>> ce502f81ba884c Chuck Lever 2022-07-08 1047 __be32 status;
>>> 243a5263014a30 Jeff Layton 2022-10-04 1048 int ret;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1049
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1050 status = fh_verify(rqstp, fhp, S_IFREG,
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1051 may_flags|NFSD_MAY_OWNER_OVERRIDE);
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1052 if (status != nfs_ok)
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1053 return status;
>>> ce502f81ba884c Chuck Lever 2022-07-08 1054 key.inode = d_inode(fhp->fh_dentry);
>>> ce502f81ba884c Chuck Lever 2022-07-08 1055 key.cred = get_current_cred();
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1056
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1057 retry:
>>> 243a5263014a30 Jeff Layton 2022-10-04 1058 rcu_read_lock();
>>> 243a5263014a30 Jeff Layton 2022-10-04 1059 nf = rhashtable_lookup(&nfsd_file_rhash_tbl, &key,
>>> ce502f81ba884c Chuck Lever 2022-07-08 1060 nfsd_file_rhash_params);
>>> ce502f81ba884c Chuck Lever 2022-07-08 1061 if (nf)
>>> ce502f81ba884c Chuck Lever 2022-07-08 1062 nf = nfsd_file_get(nf);
>>> 243a5263014a30 Jeff Layton 2022-10-04 1063 rcu_read_unlock();
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1064 if (nf)
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1065 goto wait_for_construction;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1066
>>> 243a5263014a30 Jeff Layton 2022-10-04 1067 nf = nfsd_file_alloc(&key, may_flags);
>>> 243a5263014a30 Jeff Layton 2022-10-04 1068 if (!nf) {
>>> 54f7df7094b329 Chuck Lever 2022-07-08 1069 status = nfserr_jukebox;
>>> 54f7df7094b329 Chuck Lever 2022-07-08 1070 goto out_status;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1071 }
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1072
>>> 243a5263014a30 Jeff Layton 2022-10-04 1073 ret = rhashtable_lookup_insert_key(&nfsd_file_rhash_tbl,
>>> 243a5263014a30 Jeff Layton 2022-10-04 1074 &key, &nf->nf_rhash,
>>> ce502f81ba884c Chuck Lever 2022-07-08 1075 nfsd_file_rhash_params);
>>> 243a5263014a30 Jeff Layton 2022-10-04 1076 if (likely(ret == 0))
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1077 goto open_file;
>>> 243a5263014a30 Jeff Layton 2022-10-04 1078
>>> 243a5263014a30 Jeff Layton 2022-10-04 1079 nfsd_file_slab_free(&nf->nf_rcu);
>>> 243a5263014a30 Jeff Layton 2022-10-04 1080 if (ret == -EEXIST)
>>> 243a5263014a30 Jeff Layton 2022-10-04 1081 goto retry;
>>> 243a5263014a30 Jeff Layton 2022-10-04 1082 trace_nfsd_file_insert_err(rqstp, key.inode, may_flags, ret);
>>> 243a5263014a30 Jeff Layton 2022-10-04 1083 status = nfserr_jukebox;
>>> 243a5263014a30 Jeff Layton 2022-10-04 1084 goto out_status;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1085
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1086 wait_for_construction:
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1087 wait_on_bit(&nf->nf_flags, NFSD_FILE_PENDING, TASK_UNINTERRUPTIBLE);
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1088
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1089 /* Did construction of this file fail? */
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1090 if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
>>> ce502f81ba884c Chuck Lever 2022-07-08 1091 trace_nfsd_file_cons_err(rqstp, key.inode, may_flags, nf);
>>> 243a5263014a30 Jeff Layton 2022-10-04 1092 if (!open_retry) {
>>> 28c7d86bb6172f Trond Myklebust 2020-01-06 1093 status = nfserr_jukebox;
>>> 28c7d86bb6172f Trond Myklebust 2020-01-06 1094 goto out;
>>> 28c7d86bb6172f Trond Myklebust 2020-01-06 1095 }
>>> 243a5263014a30 Jeff Layton 2022-10-04 1096 open_retry = false;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1097 nfsd_file_put_noref(nf);
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1098 goto retry;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1099 }
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1100
>>> 4a0e73e635e3f3 Chuck Lever 2022-07-08 1101 nfsd_file_lru_remove(nf);
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1102 this_cpu_inc(nfsd_file_cache_hits);
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1103
>>> 23ba98de6dcec6 Jeff Layton 2022-07-29 1104 status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags));
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1105 out:
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1106 if (status == nfs_ok) {
>>> 29d4bdbbb910f3 Chuck Lever 2022-07-08 1107 if (open)
>>> 29d4bdbbb910f3 Chuck Lever 2022-07-08 1108 this_cpu_inc(nfsd_file_acquisitions);
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1109 *pnf = nf;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1110 } else {
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1111 nfsd_file_put(nf);
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1112 nf = NULL;
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1113 }
>>> 65294c1f2c5e72 Jeff Layton 2019-08-18 1114
>>> 54f7df7094b329 Chuck Lever 2022-07-08 1115 out_status:
>>> ce502f81ba884c Chuck Lever 2022-07-08 1116 put_cred(key.cred);
>>> be0230069fcbf7 Chuck Lever 2022-07-08 1117 if (open)
>>> ce502f81ba884c Chuck Lever 2022-07-08 @1118 trace_nfsd_file_acquire(rqstp, key.inode, may_flags, nf, status);
>>>
>>> Passing freed pointers to the trace code is a border line case... Not
>>> sure if we care.
>>
>> Speaking only for NFSD, let me echo Jeff and say yes, we care.
>>
>> In general, I think Linux users/customers and of course our fellow
>> sustaining engineers want to feel confident that enabling tracing
>> on a production kernel isn't going to result in less stability.
>>
>> Thanks for the report!
>
> Your welcome. What I meant was that it's only a problem if we
> dereference the pointer... (I haven't used tracing output so I wasn't
> sure on this).
Following up: yes, the @nf parameter happens to be dereferenced inside
the nfsd_file_acquire tracepoint (the @inode parameter is not, though).
--
Chuck Lever
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