Fix unsafe string operations

Coverity caught unsafe use of `strcpy()` in `ztest_dmu_objset_own()`,
`nfs_init_tmpfile()` and `dump_snapshot()`. It also caught an unsafe use
of `strlcat()` in `nfs_init_tmpfile()`.

Inspired by this, I did an audit of every single usage of `strcpy()` and
`strcat()` in the code. If I could not prove that the usage was safe, I
changed the code to use either `strlcpy()` or `strlcat()`, depending on
which function was originally used. In some cases, `snprintf()` was used
to replace multiple uses of `strcat` because it was cleaner.

Whenever I changed a function, I preferred to use `sizeof(dst)` when the
compiler is able to provide the string size via that. When it could not
because the string was passed by a caller, I checked the entire call
tree of the function to find out how big the buffer was and hard coded
it. Hardcoding is less than ideal, but it is safe unless someone shrinks
the buffer sizes being passed.

Additionally, Coverity reported three more string related issues:

 * It caught a case where we do an overlapping memory copy in a call to
   `snprintf()`. We fix that via `kmem_strdup()` and `kmem_strfree()`.

 * It caught `sizeof (buf)` being used instead of `buflen` in
   `zdb_nicenum()`'s call to `zfs_nicenum()`, which is passed to
   `snprintf()`. We change that to pass `buflen`.

 * It caught a theoretical unterminated string passed to `strcmp()`.
   This one is likely a false positive, but we have the information
   needed to do this more safely, so we change this to silence the false
   positive not just in coverity, but potentially other static analysis
   tools too. We switch to `strncmp()`.

 * There was a false positive in tests/zfs-tests/cmd/dir_rd_update.c. We
   suppress it by switching to `snprintf()` since other static analysis
   tools might complain about it too. Interestingly, there is a possible
   real bug there too, since it assumes that the passed directory path
   ends with '/'. We add a '/' to fix that potential bug.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Richard Yao <[email protected]>
Closes #13913 

13 files changed, 43 insertions, 37 deletions

diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
index ba746e8a3..96db9c4b9 100644
--- a/cmd/zdb/zdb.c
+++ b/cmd/zdb/zdb.c
@@ -985,7 +985,7 @@ zdb_nicenum(uint64_t num, char *buf, size_t buflen)
 	if (dump_opt['P'])
 		(void) snprintf(buf, buflen, "%llu", (longlong_t)num);
 	else
-		nicenum(num, buf, sizeof (buf));
+		nicenum(num, buf, buflen);
 }
 
 static const char histo_stars[] = "****************************************";
diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index 74bdd796e..7bda3f529 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -2459,7 +2459,8 @@ upgrade_set_callback(zfs_handle_t *zhp, void *data)
 			cb->cb_numupgraded++;
 		else
 			cb->cb_numfailed++;
-		(void) strcpy(cb->cb_lastfs, zfs_get_name(zhp));
+		(void) strlcpy(cb->cb_lastfs, zfs_get_name(zhp),
+		    sizeof (cb->cb_lastfs));
 	} else if (version > cb->cb_version) {
 		/* can't downgrade */
 		(void) printf(gettext("%s: can not be downgraded; "
diff --git a/cmd/zinject/translate.c b/cmd/zinject/translate.c
index cd4264bdc..c63caedd1 100644
--- a/cmd/zinject/translate.c
+++ b/cmd/zinject/translate.c
@@ -115,12 +115,12 @@ parse_pathname(const char *inpath, char *dataset, char *relpath,
 		return (-1);
 	}
 
-	(void) strcpy(dataset, mp.mnt_special);
+	(void) strlcpy(dataset, mp.mnt_special, MAXNAMELEN);
 
 	rel = fullpath + strlen(mp.mnt_mountp);
 	if (rel[0] == '/')
 		rel++;
-	(void) strcpy(relpath, rel);
+	(void) strlcpy(relpath, rel, MAXPATHLEN);
 
 	return (0);
 }
@@ -258,7 +258,7 @@ translate_record(err_type_t type, const char *object, const char *range,
 		}
 
 		dataset[0] = '\0';
-		(void) strcpy(poolname, object);
+		(void) strlcpy(poolname, object, MAXNAMELEN);
 		return (0);
 	}
 
@@ -298,7 +298,7 @@ translate_record(err_type_t type, const char *object, const char *range,
 	/*
 	 * Copy the pool name
 	 */
-	(void) strcpy(poolname, dataset);
+	(void) strlcpy(poolname, dataset, MAXNAMELEN);
 	if ((slash = strchr(poolname, '/')) != NULL)
 		*slash = '\0';
 
diff --git a/cmd/ztest.c b/cmd/ztest.c
index b67c765a1..436f5c156 100644
--- a/cmd/ztest.c
+++ b/cmd/ztest.c
@@ -1544,7 +1544,7 @@ ztest_dmu_objset_own(const char *name, dmu_objset_type_t type,
 	char *cp = NULL;
 	char ddname[ZFS_MAX_DATASET_NAME_LEN];
 
-	strcpy(ddname, name);
+	strlcpy(ddname, name, sizeof (ddname));
 	cp = strchr(ddname, '@');
 	if (cp != NULL)
 		*cp = '\0';
@@ -3667,7 +3667,7 @@ ztest_vdev_attach_detach(ztest_ds_t *zd, uint64_t id)
 	oldguid = oldvd->vdev_guid;
 	oldsize = vdev_get_min_asize(oldvd);
 	oldvd_is_log = oldvd->vdev_top->vdev_islog;
-	(void) strcpy(oldpath, oldvd->vdev_path);
+	(void) strlcpy(oldpath, oldvd->vdev_path, MAXPATHLEN);
 	pvd = oldvd->vdev_parent;
 	pguid = pvd->vdev_guid;
 
@@ -3703,7 +3703,7 @@ ztest_vdev_attach_detach(ztest_ds_t *zd, uint64_t id)
 		if (newvd->vdev_ops == &vdev_draid_spare_ops)
 			newvd_is_dspare = B_TRUE;
 
-		(void) strcpy(newpath, newvd->vdev_path);
+		(void) strlcpy(newpath, newvd->vdev_path, MAXPATHLEN);
 	} else {
 		(void) snprintf(newpath, MAXPATHLEN, ztest_dev_template,
 		    ztest_opts.zo_dir, ztest_opts.zo_pool,
@@ -6145,8 +6145,8 @@ ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
 		}
 		vd0 = sav->sav_vdevs[ztest_random(sav->sav_count)];
 		guid0 = vd0->vdev_guid;
-		(void) strcpy(path0, vd0->vdev_path);
-		(void) strcpy(pathrand, vd0->vdev_path);
+		(void) strlcpy(path0, vd0->vdev_path, MAXPATHLEN);
+		(void) strlcpy(pathrand, vd0->vdev_path, MAXPATHLEN);
 
 		leaf = 0;
 		leaves = 1;
diff --git a/contrib/pam_zfs_key/pam_zfs_key.c b/contrib/pam_zfs_key/pam_zfs_key.c
index aaca67008..e0bbd249a 100644
--- a/contrib/pam_zfs_key/pam_zfs_key.c
+++ b/contrib/pam_zfs_key/pam_zfs_key.c
@@ -558,9 +558,8 @@ zfs_key_config_get_dataset(zfs_key_config_t *config)
 		return (NULL);
 	}
 	ret[0] = 0;
-	strcat(ret, config->homes_prefix);
-	strcat(ret, "/");
-	strcat(ret, config->username);
+	(void) snprintf(ret, len + 1, "%s/%s", config->homes_prefix,
+	    config->username);
 	return (ret);
 }
 
diff --git a/lib/libshare/nfs.c b/lib/libshare/nfs.c
index bbaea93fc..3251913cb 100644
--- a/lib/libshare/nfs.c
+++ b/lib/libshare/nfs.c
@@ -95,8 +95,8 @@ nfs_init_tmpfile(const char *prefix, const char *mdir, struct tmpfile *tmpf)
 		return (B_FALSE);
 	}
 
-	strcpy(tmpf->name, prefix);
-	strcat(tmpf->name, ".XXXXXXXX");
+	strlcpy(tmpf->name, prefix, sizeof (tmpf->name));
+	strlcat(tmpf->name, ".XXXXXXXX", sizeof (tmpf->name) - strlen(prefix));
 
 	int fd = mkostemp(tmpf->name, O_CLOEXEC);
 	if (fd == -1) {
diff --git a/lib/libspl/os/freebsd/mnttab.c b/lib/libspl/os/freebsd/mnttab.c
index f0cc04d89..a4673084a 100644
--- a/lib/libspl/os/freebsd/mnttab.c
+++ b/lib/libspl/os/freebsd/mnttab.c
@@ -74,7 +74,7 @@ hasmntopt(struct mnttab *mnt, const char *opt)
 
 	if (mnt->mnt_mntopts == NULL)
 		return (NULL);
-	(void) strcpy(opts, mnt->mnt_mntopts);
+	(void) strlcpy(opts, mnt->mnt_mntopts, MNT_LINE_MAX);
 	f = mntopt(&opts);
 	for (; *f; f = mntopt(&opts)) {
 		if (strncmp(opt, f, strlen(opt)) == 0)
diff --git a/lib/libzfs/libzfs_sendrecv.c b/lib/libzfs/libzfs_sendrecv.c
index 9d514a37e..d63a9e1a4 100644
--- a/lib/libzfs/libzfs_sendrecv.c
+++ b/lib/libzfs/libzfs_sendrecv.c
@@ -1175,7 +1175,7 @@ dump_snapshot(zfs_handle_t *zhp, void *arg)
 			return (-1);
 	}
 
-	(void) strcpy(sdd->prevsnap, thissnap);
+	(void) strlcpy(sdd->prevsnap, thissnap, sizeof (sdd->prevsnap));
 	sdd->prevsnap_obj = zfs_prop_get_int(zhp, ZFS_PROP_OBJSETID);
 	zfs_close(zhp);
 	return (err);
@@ -1736,7 +1736,7 @@ zfs_send_resume_impl_cb_impl(libzfs_handle_t *hdl, sendflags_t *flags,
 	(void) nvlist_lookup_uint64(resume_nvl, "fromguid", &fromguid);
 
 	if (flags->saved) {
-		(void) strcpy(name, toname);
+		(void) strlcpy(name, toname, sizeof (name));
 	} else {
 		error = guid_to_name(hdl, toname, toguid, B_FALSE, name);
 		if (error != 0) {
@@ -2880,7 +2880,7 @@ recv_rename(libzfs_handle_t *hdl, const char *name, const char *tryname,
 		goto out;
 
 	if (tryname) {
-		(void) strcpy(newname, tryname);
+		(void) strlcpy(newname, tryname, ZFS_MAX_DATASET_NAME_LEN);
 		if (flags->verbose) {
 			(void) printf("attempting rename %s to %s\n",
 			    name, newname);
@@ -4331,7 +4331,7 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 		err = nvlist_lookup_string(rcvprops,
 		    zfs_prop_to_name(ZFS_PROP_KEYLOCATION), &keylocation);
 		if (err == 0) {
-			strcpy(tmp_keylocation, keylocation);
+			strlcpy(tmp_keylocation, keylocation, MAXNAMELEN);
 			(void) nvlist_remove_all(rcvprops,
 			    zfs_prop_to_name(ZFS_PROP_KEYLOCATION));
 		}
@@ -4498,18 +4498,20 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 		(void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
 		    "cannot receive new filesystem stream"));
 
-		(void) strcpy(name, destsnap);
+		(void) strlcpy(name, destsnap, sizeof (name));
 		cp = strrchr(name, '/');
 		if (cp)
 			*cp = '\0';
 		if (cp &&
 		    !zfs_dataset_exists(hdl, name, ZFS_TYPE_DATASET)) {
 			char suffix[ZFS_MAX_DATASET_NAME_LEN];
-			(void) strcpy(suffix, strrchr(destsnap, '/'));
+			(void) strlcpy(suffix, strrchr(destsnap, '/'),
+			    sizeof (suffix));
 			if (guid_to_name(hdl, name, parent_snapguid,
 			    B_FALSE, destsnap) == 0) {
 				*strchr(destsnap, '@') = '\0';
-				(void) strcat(destsnap, suffix);
+				(void) strlcat(destsnap, suffix,
+				    sizeof (destsnap) - strlen(destsnap));
 			}
 		}
 	} else {
@@ -4527,7 +4529,7 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 			    "cannot receive incremental stream"));
 		}
 
-		(void) strcpy(name, destsnap);
+		(void) strlcpy(name, destsnap, sizeof (name));
 		*strchr(name, '@') = '\0';
 
 		/*
@@ -4539,16 +4541,18 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 		    strlen(sendfs)) != '\0' && *chopprefix != '@')) &&
 		    !zfs_dataset_exists(hdl, name, ZFS_TYPE_DATASET)) {
 			char snap[ZFS_MAX_DATASET_NAME_LEN];
-			(void) strcpy(snap, strchr(destsnap, '@'));
+			(void) strlcpy(snap, strchr(destsnap, '@'),
+			    sizeof (snap));
 			if (guid_to_name(hdl, name, drrb->drr_fromguid,
 			    B_FALSE, destsnap) == 0) {
 				*strchr(destsnap, '@') = '\0';
-				(void) strcat(destsnap, snap);
+				(void) strlcat(destsnap, snap,
+				    sizeof (destsnap) - strlen(destsnap));
 			}
 		}
 	}
 
-	(void) strcpy(name, destsnap);
+	(void) strlcpy(name, destsnap, sizeof (name));
 	*strchr(name, '@') = '\0';
 
 	redacted = DMU_GET_FEATUREFLAGS(drrb->drr_versioninfo) &
@@ -4930,7 +4934,7 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 	if (err == 0 && snapprops_nvlist) {
 		zfs_cmd_t zc = {"\0"};
 
-		(void) strcpy(zc.zc_name, destsnap);
+		(void) strlcpy(zc.zc_name, destsnap, sizeof (zc.zc_name));
 		zc.zc_cookie = B_TRUE; /* received */
 		zcmd_write_src_nvlist(hdl, &zc, snapprops_nvlist);
 		(void) zfs_ioctl(hdl, ZFS_IOC_SET_PROP, &zc);
diff --git a/lib/libzfs/os/linux/libzfs_util_os.c b/lib/libzfs/os/linux/libzfs_util_os.c
index 4a44aa1f1..99faae668 100644
--- a/lib/libzfs/os/linux/libzfs_util_os.c
+++ b/lib/libzfs/os/linux/libzfs_util_os.c
@@ -145,8 +145,8 @@ libzfs_load_module(void)
 		if (pfds[0].revents & POLLIN) {
 			verify(read(ino, ev, evsz) >
 			    sizeof (struct inotify_event));
-			if (strcmp(ev->name, &ZFS_DEV[sizeof (ZFS_DEVDIR)])
-			    == 0) {
+			if (strncmp(ev->name, &ZFS_DEV[sizeof (ZFS_DEVDIR)],
+			    ev->len) == 0) {
 				ret = 0;
 				break;
 			}
diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index 95377fa46..4ee3ffc35 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -3016,7 +3016,8 @@ dmu_send_estimate_fast(dsl_dataset_t *origds, dsl_dataset_t *fromds,
 
 		dsl_dataset_name(origds, dsname);
 		(void) strcat(dsname, "/");
-		(void) strcat(dsname, recv_clone_name);
+		(void) strlcat(dsname, recv_clone_name,
+		    sizeof (dsname) - strlen(dsname));
 
 		err = dsl_dataset_hold(origds->ds_dir->dd_pool,
 		    dsname, FTAG, &ds);
diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index 64bc70c24..c944db2c5 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -2740,6 +2740,8 @@ dsl_get_mountpoint(dsl_dataset_t *ds, const char *dsname, char *value,
 		    relpath[0] != '\0'))
 			mnt = value + 1;
 
+		mnt = kmem_strdup(mnt);
+
 		if (relpath[0] == '\0') {
 			(void) snprintf(value, ZAP_MAXVALUELEN, "%s%s",
 			    root, mnt);
@@ -2749,6 +2751,7 @@ dsl_get_mountpoint(dsl_dataset_t *ds, const char *dsname, char *value,
 			    relpath);
 		}
 		kmem_free(buf, ZAP_MAXVALUELEN);
+		kmem_strfree(mnt);
 	}
 
 	return (0);
diff --git a/tests/zfs-tests/cmd/dir_rd_update.c b/tests/zfs-tests/cmd/dir_rd_update.c
index 80c395cc6..c0d283105 100644
--- a/tests/zfs-tests/cmd/dir_rd_update.c
+++ b/tests/zfs-tests/cmd/dir_rd_update.c
@@ -63,13 +63,12 @@ main(int argc, char **argv)
 	}
 
 	cp1 = argv[1];
-	if (strlen(cp1) >= (sizeof (dirpath) - strlen("TMP_DIR"))) {
+	if (strlen(cp1) >= (sizeof (dirpath) - strlen("/TMP_DIR"))) {
 		(void) printf("The string length of mount point is "
 		    "too large\n");
 		exit(-1);
 	}
-	(void) strcpy(&dirpath[0], (const char *)cp1);
-	(void) strcat(&dirpath[strlen(dirpath)], "TMP_DIR");
+	(void) snprintf(dirpath, sizeof (dirpath), "%s/TMP_DIR", cp1);
 
 	ret = mkdir(dirpath, 0777);
 	if (ret != 0) {
diff --git a/tests/zfs-tests/cmd/mmap_sync.c b/tests/zfs-tests/cmd/mmap_sync.c
index 618f1284a..e4d190aef 100644
--- a/tests/zfs-tests/cmd/mmap_sync.c
+++ b/tests/zfs-tests/cmd/mmap_sync.c
@@ -73,8 +73,7 @@ main(int argc, char *argv[])
 	filepath[0] = '\0';
 	char *file = &filepath[0];
 
-	strcat(file, testdir);
-	strcat(file, "/msync_file");
+	(void) snprintf(file, 512, "%s/msync_file", testdir);
 
 	const int LEN = 8;
 	cleanup(file);