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Date: Mon, 7 Nov 2022 10:48:10 +0300
From: Dan Carpenter <error27@...il.com>
To: Chuck Lever III <chuck.lever@...cle.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 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).
regards,
dan carpenter
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