Re: [nfs-utils PATCH v3 1/2] gssd: deal with failed thread creation

Steve Dickson <steved@xxxxxxxxxx> · Thu, 10 Jun 2021 12:12:54 -0400

On 5/27/21 3:11 PM, Scott Mayhew wrote:
If we fail to create a thread to handle an upcall, we still need to do a
downcall to tell the kernel about the failure, otherwise the process
that is trying to establish gss credentials will hang.

This patch shifts the thread creation down a level in the call chain so
now the main thread does a little more work up front (reading & parsing
the data from the pipefs file) so it has the info it needs to be able
to do the error downcall.

Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
Committed... (tag: nfs-utils-2-5-4-rc6)

steved.
---
  utils/gssd/gssd.c      |  83 +-----------------
  utils/gssd/gssd.h      |  11 ++-
  utils/gssd/gssd_proc.c | 188 +++++++++++++++++++++++++++++++++--------
  3 files changed, 164 insertions(+), 118 deletions(-)

diff --git a/utils/gssd/gssd.c b/utils/gssd/gssd.c
index 1541d371..eb440470 100644
--- a/utils/gssd/gssd.c
+++ b/utils/gssd/gssd.c
@@ -364,7 +364,7 @@ out:
  /* Actually frees clp and fields that might be used from other
   * threads if was last reference.
   */
-static void
+void
  gssd_free_client(struct clnt_info *clp)
  {
  	int refcnt;
@@ -416,55 +416,6 @@ gssd_destroy_client(struct clnt_info *clp)
  
  static void gssd_scan(void);
  
-static int
-start_upcall_thread(void (*func)(struct clnt_upcall_info *), void *info)
-{
-	pthread_attr_t attr;
-	pthread_t th;
-	int ret;
-
-	ret = pthread_attr_init(&attr);
-	if (ret != 0) {
-		printerr(0, "ERROR: failed to init pthread attr: ret %d: %s\n",
-			 ret, strerror(errno));
-		return ret;
-	}
-	ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-	if (ret != 0) {
-		printerr(0, "ERROR: failed to create pthread attr: ret %d: "
-			 "%s\n", ret, strerror(errno));
-		return ret;
-	}
-
-	ret = pthread_create(&th, &attr, (void *)func, (void *)info);
-	if (ret != 0)
-		printerr(0, "ERROR: pthread_create failed: ret %d: %s\n",
-			 ret, strerror(errno));
-	return ret;
-}
-
-static struct clnt_upcall_info *alloc_upcall_info(struct clnt_info *clp)
-{
-	struct clnt_upcall_info *info;
-
-	info = malloc(sizeof(struct clnt_upcall_info));
-	if (info == NULL)
-		return NULL;
-
-	pthread_mutex_lock(&clp_lock);
-	clp->refcount++;
-	pthread_mutex_unlock(&clp_lock);
-	info->clp = clp;
-
-	return info;
-}
-
-void free_upcall_info(struct clnt_upcall_info *info)
-{
-	gssd_free_client(info->clp);
-	free(info);
-}
-
  /* For each upcall read the upcall info into the buffer, then create a
   * thread in a detached state so that resources are released back into
   * the system without the need for a join.
@@ -473,44 +424,16 @@ static void
  gssd_clnt_gssd_cb(int UNUSED(fd), short UNUSED(which), void *data)
  {
  	struct clnt_info *clp = data;
-	struct clnt_upcall_info *info;
-
-	info = alloc_upcall_info(clp);
-	if (info == NULL)
-		return;
  
-	info->lbuflen = read(clp->gssd_fd, info->lbuf, sizeof(info->lbuf));
-	if (info->lbuflen <= 0 || info->lbuf[info->lbuflen-1] != '\n') {
-		printerr(0, "WARNING: %s: failed reading request\n", __func__);
-		free_upcall_info(info);
-		return;
-	}
-	info->lbuf[info->lbuflen-1] = 0;
-
-	if (start_upcall_thread(handle_gssd_upcall, info))
-		free_upcall_info(info);
+	handle_gssd_upcall(clp);
  }
  
  static void
  gssd_clnt_krb5_cb(int UNUSED(fd), short UNUSED(which), void *data)
  {
  	struct clnt_info *clp = data;
-	struct clnt_upcall_info *info;
-
-	info = alloc_upcall_info(clp);
-	if (info == NULL)
-		return;
-
-	if (read(clp->krb5_fd, &info->uid,
-			sizeof(info->uid)) < (ssize_t)sizeof(info->uid)) {
-		printerr(0, "WARNING: %s: failed reading uid from krb5 "
-			 "upcall pipe: %s\n", __func__, strerror(errno));
-		free_upcall_info(info);
-		return;
-	}
  
-	if (start_upcall_thread(handle_krb5_upcall, info))
-		free_upcall_info(info);
+	handle_krb5_upcall(clp);
  }
  
  static struct clnt_info *
diff --git a/utils/gssd/gssd.h b/utils/gssd/gssd.h
index 1e8c58d4..6d53647e 100644
--- a/utils/gssd/gssd.h
+++ b/utils/gssd/gssd.h
@@ -84,14 +84,17 @@ struct clnt_info {
  
  struct clnt_upcall_info {
  	struct clnt_info 	*clp;
-	char			lbuf[RPC_CHAN_BUF_SIZE];
-	int			lbuflen;
  	uid_t			uid;
+	int			fd;
+	char			*srchost;
+	char			*target;
+	char			*service;
  };
  
-void handle_krb5_upcall(struct clnt_upcall_info *clp);
-void handle_gssd_upcall(struct clnt_upcall_info *clp);
+void handle_krb5_upcall(struct clnt_info *clp);
+void handle_gssd_upcall(struct clnt_info *clp);
  void free_upcall_info(struct clnt_upcall_info *info);
+void gssd_free_client(struct clnt_info *clp);
  
  
  #endif /* _RPC_GSSD_H_ */
diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c
index e830f497..ebec414e 100644
--- a/utils/gssd/gssd_proc.c
+++ b/utils/gssd/gssd_proc.c
@@ -80,6 +80,8 @@
  #include "nfslib.h"
  #include "gss_names.h"
  
+extern pthread_mutex_t clp_lock;
+
  /* Encryption types supported by the kernel rpcsec_gss code */
  int num_krb5_enctypes = 0;
  krb5_enctype *krb5_enctypes = NULL;
@@ -723,22 +725,133 @@ out_return_error:
  	goto out;
  }
  
-void
-handle_krb5_upcall(struct clnt_upcall_info *info)
+static struct clnt_upcall_info *
+alloc_upcall_info(struct clnt_info *clp, uid_t uid, int fd, char *srchost,
+		  char *target, char *service)
  {
-	struct clnt_info *clp = info->clp;
+	struct clnt_upcall_info *info;
+
+	info = malloc(sizeof(struct clnt_upcall_info));
+	if (info == NULL)
+		return NULL;
+
+	memset(info, 0, sizeof(*info));
+	pthread_mutex_lock(&clp_lock);
+	clp->refcount++;
+	pthread_mutex_unlock(&clp_lock);
+	info->clp = clp;
+	info->uid = uid;
+	info->fd = fd;
+	if (srchost) {
+		info->srchost = strdup(srchost);
+		if (info->srchost == NULL)
+			goto out_info;
+	}
+	if (target) {
+		info->target = strdup(target);
+		if (info->target == NULL)
+			goto out_srchost;
+	}
+	if (service) {
+		info->service = strdup(service);
+		if (info->service == NULL)
+			goto out_target;
+	}
+
+out:
+	return info;
+
+out_target:
+	if (info->target)
+		free(info->target);
+out_srchost:
+	if (info->srchost)
+		free(info->srchost);
+out_info:
+	free(info);
+	info = NULL;
+	goto out;
+}
  
-	printerr(2, "\n%s: uid %d (%s)\n", __func__, info->uid, clp->relpath);
+void free_upcall_info(struct clnt_upcall_info *info)
+{
+	gssd_free_client(info->clp);
+	if (info->service)
+		free(info->service);
+	if (info->target)
+		free(info->target);
+	if (info->srchost)
+		free(info->srchost);
+	free(info);
+}
  
-	process_krb5_upcall(clp, info->uid, clp->krb5_fd, NULL, NULL, NULL);
+static void
+gssd_work_thread_fn(struct clnt_upcall_info *info)
+{
+	process_krb5_upcall(info->clp, info->uid, info->fd, info->srchost, info->target, info->service);
  	free_upcall_info(info);
  }
  
+static int
+start_upcall_thread(void (*func)(struct clnt_upcall_info *), void *info)
+{
+	pthread_attr_t attr;
+	pthread_t th;
+	int ret;
+
+	ret = pthread_attr_init(&attr);
+	if (ret != 0) {
+		printerr(0, "ERROR: failed to init pthread attr: ret %d: %s\n",
+			 ret, strerror(errno));
+		return ret;
+	}
+	ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+	if (ret != 0) {
+		printerr(0, "ERROR: failed to create pthread attr: ret %d: "
+			 "%s\n", ret, strerror(errno));
+		return ret;
+	}
+
+	ret = pthread_create(&th, &attr, (void *)func, (void *)info);
+	if (ret != 0)
+		printerr(0, "ERROR: pthread_create failed: ret %d: %s\n",
+			 ret, strerror(errno));
+	return ret;
+}
+
+void
+handle_krb5_upcall(struct clnt_info *clp)
+{
+	uid_t			uid;
+	struct clnt_upcall_info	*info;
+	int			err;
+
+	if (read(clp->krb5_fd, &uid, sizeof(uid)) < (ssize_t)sizeof(uid)) {
+		printerr(0, "WARNING: failed reading uid from krb5 "
+			    "upcall pipe: %s\n", strerror(errno));
+		return;
+	}
+	printerr(2, "\n%s: uid %d (%s)\n", __func__, uid, clp->relpath);
+
+	info = alloc_upcall_info(clp, uid, clp->krb5_fd, NULL, NULL, NULL);
+	if (info == NULL) {
+		printerr(0, "%s: failed to allocate clnt_upcall_info\n", __func__);
+		do_error_downcall(clp->krb5_fd, uid, -EACCES);
+		return;
+	}
+	err = start_upcall_thread(gssd_work_thread_fn, info);
+	if (err != 0) {
+		do_error_downcall(clp->krb5_fd, uid, -EACCES);
+		free_upcall_info(info);
+	}
+}
+
  void
-handle_gssd_upcall(struct clnt_upcall_info *info)
+handle_gssd_upcall(struct clnt_info *clp)
  {
-	struct clnt_info	*clp = info->clp;
  	uid_t			uid;
+	char			lbuf[RPC_CHAN_BUF_SIZE];
+	int			lbuflen = 0;
  	char			*p;
  	char			*mech = NULL;
  	char			*uidstr = NULL;
@@ -746,20 +859,22 @@ handle_gssd_upcall(struct clnt_upcall_info *info)
  	char			*service = NULL;
  	char			*srchost = NULL;
  	char			*enctypes = NULL;
-	char			*upcall_str;
-	char			*pbuf = info->lbuf;
  	pthread_t tid = pthread_self();
+	struct clnt_upcall_info	*info;
+	int			err;
  
-	printerr(2, "\n%s(0x%x): '%s' (%s)\n", __func__, tid,
-		info->lbuf, clp->relpath);
-
-	upcall_str = strdup(info->lbuf);
-	if (upcall_str == NULL) {
-		printerr(0, "ERROR: malloc failure\n");
-		goto out_nomem;
+	lbuflen = read(clp->gssd_fd, lbuf, sizeof(lbuf));
+	if (lbuflen <= 0 || lbuf[lbuflen-1] != '\n') {
+		printerr(0, "WARNING: handle_gssd_upcall: "
+			    "failed reading request\n");
+		return;
  	}
+	lbuf[lbuflen-1] = 0;
+
+	printerr(2, "\n%s(0x%x): '%s' (%s)\n", __func__, tid,
+		 lbuf, clp->relpath);
  
-	while ((p = strsep(&pbuf, " "))) {
+	for (p = strtok(lbuf, " "); p; p = strtok(NULL, " ")) {
  		if (!strncmp(p, "mech=", strlen("mech=")))
  			mech = p + strlen("mech=");
  		else if (!strncmp(p, "uid=", strlen("uid=")))
@@ -777,8 +892,8 @@ handle_gssd_upcall(struct clnt_upcall_info *info)
  	if (!mech || strlen(mech) < 1) {
  		printerr(0, "WARNING: handle_gssd_upcall: "
  			    "failed to find gss mechanism name "
-			    "in upcall string '%s'\n", upcall_str);
-		goto out;
+			    "in upcall string '%s'\n", lbuf);
+		return;
  	}
  
  	if (uidstr) {
@@ -790,21 +905,21 @@ handle_gssd_upcall(struct clnt_upcall_info *info)
  	if (!uidstr) {
  		printerr(0, "WARNING: handle_gssd_upcall: "
  			    "failed to find uid "
-			    "in upcall string '%s'\n", upcall_str);
-		goto out;
+			    "in upcall string '%s'\n", lbuf);
+		return;
  	}
  
  	if (enctypes && parse_enctypes(enctypes) != 0) {
  		printerr(0, "WARNING: handle_gssd_upcall: "
  			 "parsing encryption types failed: errno %d\n", errno);
-		goto out;
+		return;
  	}
  
  	if (target && strlen(target) < 1) {
  		printerr(0, "WARNING: handle_gssd_upcall: "
  			 "failed to parse target name "
-			 "in upcall string '%s'\n", upcall_str);
-		goto out;
+			 "in upcall string '%s'\n", lbuf);
+		return;
  	}
  
  	/*
@@ -818,21 +933,26 @@ handle_gssd_upcall(struct clnt_upcall_info *info)
  	if (service && strlen(service) < 1) {
  		printerr(0, "WARNING: handle_gssd_upcall: "
  			 "failed to parse service type "
-			 "in upcall string '%s'\n", upcall_str);
-		goto out;
+			 "in upcall string '%s'\n", lbuf);
+		return;
  	}
  
-	if (strcmp(mech, "krb5") == 0 && clp->servername)
-		process_krb5_upcall(clp, uid, clp->gssd_fd, srchost, target, service);
-	else {
+	if (strcmp(mech, "krb5") == 0 && clp->servername) {
+		info = alloc_upcall_info(clp, uid, clp->gssd_fd, srchost, target, service);
+		if (info == NULL) {
+			printerr(0, "%s: failed to allocate clnt_upcall_info\n", __func__);
+			do_error_downcall(clp->gssd_fd, uid, -EACCES);
+			return;
+		}
+		err = start_upcall_thread(gssd_work_thread_fn, info);
+		if (err != 0) {
+			do_error_downcall(clp->gssd_fd, uid, -EACCES);
+			free_upcall_info(info);
+		}
+	} else {
  		if (clp->servername)
  			printerr(0, "WARNING: handle_gssd_upcall: "
  				 "received unknown gss mech '%s'\n", mech);
  		do_error_downcall(clp->gssd_fd, uid, -EACCES);
  	}
-out:
-	free(upcall_str);
-out_nomem:
-	free_upcall_info(info);
-	return;
  }








