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[PATCH] nss: Do not set errno to 0 in get* functions [BZ #21898]

• From: fweimer at redhat dot com (Florian Weimer)
• To: libc-alpha at sourceware dot org
• Date: Wed, 09 Aug 2017 17:27:21 +0200
• Subject: [PATCH] nss: Do not set errno to 0 in get* functions [BZ #21898]
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Some of the get* functions are in POSIX, and POSIX functions mustnot set errno to 0.Callers are expected to set errno to 0 or another invalid valuethemselves in order to detect the “successful lookup, but no data”case.2017-08-09  Florian Weimer  <fweimer@redhat.com>[BZ #21898]* nss/getXXbyYY.c (FUNCTION_NAME): Check return code from theinternal function and restore errno if the return code is zero.Set h_errno to NETDB_INTERNAL more consistently.* nss/getXXbyYY_r.c (REENTRANT_NAME): Do not set errno to zero.Restore errno on success.* pwd/getpw.c (__getpw): Set errno to zero if a successful lookupdid not find anything.diff --git a/nss/getXXbyYY.c b/nss/getXXbyYY.cindex 26ee726..254ec2c 100644--- a/nss/getXXbyYY.c+++ b/nss/getXXbyYY.c@@ -95,13 +95,19 @@ FUNCTION_NAME (ADD_PARAMS)   static LOOKUP_TYPE resbuf;   LOOKUP_TYPE *result; +  /* This function must save and restore errno for NULL return values.+     *Preservation in the _r function is not sufficient because the _r+     *function can be called multiple times until it stops returning+     *ERANGE, clobbering errno.  */+  int saved_errno = errno;+ #ifdef HANDLE_DIGITS_DOTS   /* Wrap both __nss_hostname_digits_dots and the actual lookup      function call in the same context.  */   struct resolv_context *res_ctx = __resolv_context_get ();   if (res_ctx == NULL)     {-# if NEED_H_ERRNO+# ifdef NEED_H_ERRNO       __set_h_errno (NETDB_INTERNAL); # endif       return NULL;@@ -115,6 +121,12 @@ FUNCTION_NAME (ADD_PARAMS)     {       buffer_size = BUFLEN;       buffer = (char *) malloc (buffer_size);+      if (buffer == NULL)+{+#ifdef NEED_H_ERRNO+  __set_h_errno (NETDB_INTERNAL);+#endif+}     }  #ifdef HANDLE_DIGITS_DOTS@@ -127,15 +139,19 @@ FUNCTION_NAME (ADD_PARAMS)     } #endif -  while (buffer != NULL- && (INTERNAL (REENTRANT_NAME) (ADD_VARIABLES, &resbuf, buffer,-buffer_size, &result H_ERRNO_VAR)-     == ERANGE)+  int rc = ENOMEM;+  while (buffer != NULL)+    {+      rc = INTERNAL (REENTRANT_NAME) (ADD_VARIABLES, &resbuf, buffer,+      buffer_size, &result H_ERRNO_VAR);+      if (rc != ERANGE #ifdef NEED_H_ERRNO- && h_errno == NETDB_INTERNAL+  || h_errno != NETDB_INTERNAL #endif  )-    {+break;++      /* Enlarge the buffer. */       char *new_buf;       buffer_size *= 2;       new_buf = (char *) realloc (buffer, buffer_size);@@ -144,6 +160,9 @@ FUNCTION_NAME (ADD_PARAMS)   /* We are out of memory.  Free the current buffer so that the      process gets a chance for a normal termination.  */   free (buffer);+#ifdef NEED_H_ERRNO+  __set_h_errno (NETDB_INTERNAL);+#endif   __set_errno (ENOMEM); }       buffer = new_buf;@@ -152,6 +171,12 @@ FUNCTION_NAME (ADD_PARAMS)   if (buffer == NULL)     result = NULL; +  /* If the call was successful, result could still be NULL if there+     is no record.  The caller can detect this by setting errno to+     zero before calling this function.  */+  if (rc == 0)+    __set_errno (saved_errno);+ #ifdef HANDLE_DIGITS_DOTS done: #endifdiff --git a/nss/getXXbyYY_r.c b/nss/getXXbyYY_r.cindex 5e3bead..0e938da 100644--- a/nss/getXXbyYY_r.c+++ b/nss/getXXbyYY_r.c@@ -211,6 +211,7 @@ INTERNAL (REENTRANT_NAME) (ADD_PARAMS, LOOKUP_TYPE *resbuf, char *buffer, #ifdef NEED_H_ERRNO   bool any_service = false; #endif+  int saved_errno = errno;  #ifdef NEED__RES   /* The HANDLE_DIGITS_DOTS case below already needs the resolver@@ -426,7 +427,13 @@ done:   else     return errno; -  __set_errno (res);+  if (res != 0)+    /* Some callers expect that a non-zero return value leaves the+       actual error code in the errno variable.  */+    __set_errno (res);+  else+    /* Preserve errno on success.  */+    __set_errno (saved_errno);   return res; } diff --git a/pwd/getpw.c b/pwd/getpw.cindex 0a73f28..cf14db9 100644--- a/pwd/getpw.c+++ b/pwd/getpw.c@@ -48,7 +48,12 @@ __getpw (__uid_t uid, char *buf)     return -1;    if (p == NULL)-    return -1;+    {+      /* No lookup error, but no data either.  This historic interface+ is expected to set errno to zero.  */+      errno = 0;+      return -1;+    }    if (sprintf (buf, "%s:%s:%lu:%lu:%s:%s:%s", p->pw_name, p->pw_passwd,        (unsigned long int) p->pw_uid, (unsigned long int) p->pw_gid,