[PATCH v2 0/3] Fixes for getnameinfo() with NI_NOFQDN

[PATCH v2 0/3] Fixes for getnameinfo() with NI_NOFQDN

[Adhemerval Zanella]

Changes from v1:
  * Keep the double-checked locking optimization.
  * Also check for strdup return for EAI_MEMORY

Adhemerval Zanella (3):
  inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566)
  inet: Remove strdupa from nrl_domainname()
  inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory

 inet/getnameinfo.c | 181 +++++++++++++++++++++++++--------------------
 1 file changed, 102 insertions(+), 79 deletions(-)

-- 
2.32.0

[PATCH v2 1/3] inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566)

[Adhemerval Zanella]

The 'not_first' is accessed on nrl_domainname() in a non atomically
way, although it is only updated after the lock is taken.

This patch fix the double-checked locking by using acquire-release
atomic operation instead of plain load and by moving the 'not_first'
store only after 'domain' is actually set.

Checked on x86_64-linux-gnu.
---
 inet/getnameinfo.c | 148 ++++++++++++++++++++++++---------------------
 1 file changed, 78 insertions(+), 70 deletions(-)

diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
index 8380d85783..5eee354200 100644
--- a/inet/getnameinfo.c
+++ b/inet/getnameinfo.c
@@ -83,104 +83,112 @@ libc_freeres_ptr (static char *domain);
    now ignored.  */
 #define DEPRECATED_NI_IDN 192
 
-static char *
-nrl_domainname (void)
+static void
+nrl_domainname_core (struct scratch_buffer *tmpbuf)
 {
-  static int not_first;
+  char *c;
+  struct hostent *h, th;
+  int herror;
 
-  if (! not_first)
+  while (__gethostbyname_r ("localhost", &th,
+			    tmpbuf->data, tmpbuf->length,
+			    &h, &herror))
     {
-      __libc_lock_define_initialized (static, lock);
-      __libc_lock_lock (lock);
-
-      if (! not_first)
+      if (herror == NETDB_INTERNAL && errno == ERANGE)
 	{
-	  char *c;
-	  struct hostent *h, th;
-	  int herror;
-	  struct scratch_buffer tmpbuf;
-
-	  scratch_buffer_init (&tmpbuf);
-	  not_first = 1;
+	  if (!scratch_buffer_grow (tmpbuf))
+	    return;
+	}
+      else
+	break;
+    }
 
-	  while (__gethostbyname_r ("localhost", &th,
-				    tmpbuf.data, tmpbuf.length,
+  if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
+    domain = __strdup (++c);
+  else
+    {
+      /* The name contains no domain information.  Use the name
+	 now to get more information.  */
+      while (__gethostname (tmpbuf->data, tmpbuf->length))
+	if (!scratch_buffer_grow (tmpbuf))
+	  return;
+
+      if ((c = strchr (tmpbuf->data, '.')) != NULL)
+	domain = __strdup (++c);
+      else
+	{
+	  /* We need to preserve the hostname.  */
+	  const char *hstname = strdupa (tmpbuf->data);
+	  while (__gethostbyname_r (hstname, &th,
+				    tmpbuf->data,
+				    tmpbuf->length,
 				    &h, &herror))
 	    {
 	      if (herror == NETDB_INTERNAL && errno == ERANGE)
 		{
-		  if (!scratch_buffer_grow (&tmpbuf))
-		    goto done;
+		  if (!scratch_buffer_grow (tmpbuf))
+		    return;
 		}
 	      else
 		break;
 	    }
 
-	  if (h && (c = strchr (h->h_name, '.')))
+	  if (h != NULL && (c = strchr(h->h_name, '.')) != NULL)
 	    domain = __strdup (++c);
 	  else
 	    {
-	      /* The name contains no domain information.  Use the name
-		 now to get more information.  */
-	      while (__gethostname (tmpbuf.data, tmpbuf.length))
-		if (!scratch_buffer_grow (&tmpbuf))
-		  goto done;
+	      struct in_addr in_addr;
 
-	      if ((c = strchr (tmpbuf.data, '.')))
-		domain = __strdup (++c);
-	      else
-		{
-		  /* We need to preserve the hostname.  */
-		  const char *hstname = strdupa (tmpbuf.data);
+	      in_addr.s_addr = htonl (INADDR_LOOPBACK);
 
-		  while (__gethostbyname_r (hstname, &th,
-					    tmpbuf.data, tmpbuf.length,
-					    &h, &herror))
+	      while (__gethostbyaddr_r ((const char *) &in_addr,
+					sizeof (struct in_addr),
+					AF_INET, &th,
+					tmpbuf->data,
+					tmpbuf->length,
+					&h, &herror))
+		{
+		  if (herror == NETDB_INTERNAL && errno == ERANGE)
 		    {
-		      if (herror == NETDB_INTERNAL && errno == ERANGE)
-			{
-			  if (!scratch_buffer_grow (&tmpbuf))
-			    goto done;
-			}
-		      else
-			break;
+		      if (!scratch_buffer_grow (tmpbuf))
+			return;
 		    }
-
-		  if (h && (c = strchr(h->h_name, '.')))
-		    domain = __strdup (++c);
 		  else
-		    {
-		      struct in_addr in_addr;
-
-		      in_addr.s_addr = htonl (INADDR_LOOPBACK);
-
-		      while (__gethostbyaddr_r ((const char *) &in_addr,
-						sizeof (struct in_addr),
-						AF_INET, &th,
-						tmpbuf.data, tmpbuf.length,
-						&h, &herror))
-			{
-			  if (herror == NETDB_INTERNAL && errno == ERANGE)
-			    {
-			      if (!scratch_buffer_grow (&tmpbuf))
-				goto done;
-			    }
-			  else
-			    break;
-			}
-
-		      if (h && (c = strchr (h->h_name, '.')))
-			domain = __strdup (++c);
-		    }
+		    break;
 		}
+
+	      if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
+		domain = __strdup (++c);
 	    }
-	done:
-	  scratch_buffer_free (&tmpbuf);
 	}
+    }
+}
 
-      __libc_lock_unlock (lock);
+static char *
+nrl_domainname (void)
+{
+  static int not_first;
+
+  if (__glibc_likely (atomic_load_acquire (&not_first) != 0))
+    return domain;
+
+  __libc_lock_define_initialized (static, lock);
+  __libc_lock_lock (lock);
+
+  if (atomic_load_relaxed (&not_first) == 0)
+    {
+      struct scratch_buffer tmpbuf;
+      scratch_buffer_init (&tmpbuf);
+
+      nrl_domainname_core (&tmpbuf);
+
+      scratch_buffer_free (&tmpbuf);
+
+      atomic_store_release (&not_first, 1);
     }
 
+  __libc_lock_unlock (lock);
+
   return domain;
 };
 
-- 
2.32.0

[PATCH v2 2/3] inet: Remove strdupa from nrl_domainname()

[Adhemerval Zanella]

We can use the already in place scratch_buffer.

Checked on x86_64-linux-gnu.
---
 inet/getnameinfo.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
index 5eee354200..2d2397e7dc 100644
--- a/inet/getnameinfo.c
+++ b/inet/getnameinfo.c
@@ -118,15 +118,15 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
       else
 	{
 	  /* We need to preserve the hostname.  */
-	  const char *hstname = strdupa (tmpbuf->data);
-	  while (__gethostbyname_r (hstname, &th,
-				    tmpbuf->data,
-				    tmpbuf->length,
+	  size_t hstnamelen = strlen (tmpbuf->data) + 1;
+	  while (__gethostbyname_r (tmpbuf->data, &th,
+				    tmpbuf->data + hstnamelen,
+				    tmpbuf->length - hstnamelen,
 				    &h, &herror))
 	    {
 	      if (herror == NETDB_INTERNAL && errno == ERANGE)
 		{
-		  if (!scratch_buffer_grow (tmpbuf))
+		  if (!scratch_buffer_grow_preserve (tmpbuf))
 		    return;
 		}
 	      else
-- 
2.32.0

[PATCH v2 3/3] inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory

[Adhemerval Zanella]

It aligns NI_NOFQDN with default behavior for getnameinfo().

Checked on x86_64-linux-gnu.
---
 inet/getnameinfo.c | 55 +++++++++++++++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 20 deletions(-)

diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
index 2d2397e7dc..2bec3263fc 100644
--- a/inet/getnameinfo.c
+++ b/inet/getnameinfo.c
@@ -83,7 +83,7 @@ libc_freeres_ptr (static char *domain);
    now ignored.  */
 #define DEPRECATED_NI_IDN 192
 
-static void
+static bool
 nrl_domainname_core (struct scratch_buffer *tmpbuf)
 {
   char *c;
@@ -97,7 +97,7 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
       if (herror == NETDB_INTERNAL && errno == ERANGE)
 	{
 	  if (!scratch_buffer_grow (tmpbuf))
-	    return;
+	    return false;
 	}
       else
 	break;
@@ -111,10 +111,13 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
 	 now to get more information.  */
       while (__gethostname (tmpbuf->data, tmpbuf->length))
 	if (!scratch_buffer_grow (tmpbuf))
-	  return;
+	  return false;
 
       if ((c = strchr (tmpbuf->data, '.')) != NULL)
-	domain = __strdup (++c);
+	{
+	  domain = __strdup (++c);
+	  return domain != NULL;
+	}
       else
 	{
 	  /* We need to preserve the hostname.  */
@@ -127,14 +130,17 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
 	      if (herror == NETDB_INTERNAL && errno == ERANGE)
 		{
 		  if (!scratch_buffer_grow_preserve (tmpbuf))
-		    return;
+		    return false;
 		}
 	      else
 		break;
 	    }
 
 	  if (h != NULL && (c = strchr(h->h_name, '.')) != NULL)
-	    domain = __strdup (++c);
+	    {
+	      domain = __strdup (++c);
+	      return domain != NULL;
+	    }
 	  else
 	    {
 	      struct in_addr in_addr;
@@ -151,20 +157,24 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
 		  if (herror == NETDB_INTERNAL && errno == ERANGE)
 		    {
 		      if (!scratch_buffer_grow (tmpbuf))
-			return;
+			return false;
 		    }
 		  else
 		    break;
 		}
 
 	      if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
-		domain = __strdup (++c);
+		{
+		  domain = __strdup (++c);
+		  return domain != NULL;
+		}
 	    }
 	}
     }
+  return true;
 }
 
-static char *
+static bool
 nrl_domainname (void)
 {
   static int not_first;
@@ -172,6 +182,8 @@ nrl_domainname (void)
   if (__glibc_likely (atomic_load_acquire (&not_first) != 0))
     return domain;
 
+  int r = true;
+
   __libc_lock_define_initialized (static, lock);
   __libc_lock_lock (lock);
 
@@ -180,16 +192,15 @@ nrl_domainname (void)
       struct scratch_buffer tmpbuf;
       scratch_buffer_init (&tmpbuf);
 
-      nrl_domainname_core (&tmpbuf);
+      if ((r = nrl_domainname_core (&tmpbuf)))
+	atomic_store_release (&not_first, 1);
 
       scratch_buffer_free (&tmpbuf);
-
-      atomic_store_release (&not_first, 1);
     }
 
   __libc_lock_unlock (lock);
 
-  return domain;
+  return r;
 };
 
 /* Copy a string to a destination buffer with length checking.  Return
@@ -285,13 +296,17 @@ gni_host_inet_name (struct scratch_buffer *tmpbuf,
 
   if (h)
     {
-      char *c;
-      if ((flags & NI_NOFQDN)
-	  && (c = nrl_domainname ())
-	  && (c = strstr (h->h_name, c))
-	  && (c != h->h_name) && (*(--c) == '.'))
-	/* Terminate the string after the prefix.  */
-	*c = '\0';
+      if (flags & NI_NOFQDN)
+	{
+	  if (!nrl_domainname ())
+	    return EAI_MEMORY;
+
+	  char *c = domain;
+	  if (c != NULL && (c = strstr (h->h_name, c))
+	       && (c != h->h_name) && (*(--c) == '.'))
+	    /* Terminate the string after the prefix.  */
+	    *c = '\0';
+	}
 
       /* If requested, convert from the IDN format.  */
       bool do_idn = flags & NI_IDN;
-- 
2.32.0

Re: [PATCH v2 3/3] inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory

[Andreas Schwab]

On Nov 12 2021, Adhemerval Zanella via Libc-alpha wrote:

> diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
> index 2d2397e7dc..2bec3263fc 100644
> --- a/inet/getnameinfo.c
> +++ b/inet/getnameinfo.c
> @@ -83,7 +83,7 @@ libc_freeres_ptr (static char *domain);
>     now ignored.  */
>  #define DEPRECATED_NI_IDN 192
>  
> -static void
> +static bool
>  nrl_domainname_core (struct scratch_buffer *tmpbuf)
>  {
>    char *c;
> @@ -97,7 +97,7 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
>        if (herror == NETDB_INTERNAL && errno == ERANGE)
>  	{
>  	  if (!scratch_buffer_grow (tmpbuf))
> -	    return;
> +	    return false;
>  	}
>        else
>  	break;
> @@ -111,10 +111,13 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
>  	 now to get more information.  */
>        while (__gethostname (tmpbuf->data, tmpbuf->length))
>  	if (!scratch_buffer_grow (tmpbuf))
> -	  return;
> +	  return false;
>  
>        if ((c = strchr (tmpbuf->data, '.')) != NULL)
> -	domain = __strdup (++c);
> +	{
> +	  domain = __strdup (++c);
> +	  return domain != NULL;
> +	}
>        else

You can remove `else' here and save a level of indentation.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

[PATCH v3] inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory

[Adhemerval Zanella]

It aligns NI_NOFQDN with default behavior for getnameinfo().

Checked on x86_64-linux-gnu.

---
Changes from v2:
  * Simplify nrl_domainname_core.
---
 inet/getnameinfo.c | 140 +++++++++++++++++++++++----------------------
 1 file changed, 72 insertions(+), 68 deletions(-)

diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
index 2d2397e7dc..acf1538a37 100644
--- a/inet/getnameinfo.c
+++ b/inet/getnameinfo.c
@@ -83,94 +83,95 @@ libc_freeres_ptr (static char *domain);
    now ignored.  */
 #define DEPRECATED_NI_IDN 192
 
-static void
+static bool
 nrl_domainname_core (struct scratch_buffer *tmpbuf)
 {
   char *c;
   struct hostent *h, th;
   int herror;
 
-  while (__gethostbyname_r ("localhost", &th,
-			    tmpbuf->data, tmpbuf->length,
+  while (__gethostbyname_r ("localhost", &th, tmpbuf->data, tmpbuf->length,
 			    &h, &herror))
     {
       if (herror == NETDB_INTERNAL && errno == ERANGE)
 	{
 	  if (!scratch_buffer_grow (tmpbuf))
-	    return;
+	    return false;
 	}
       else
 	break;
     }
 
   if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
-    domain = __strdup (++c);
-  else
     {
-      /* The name contains no domain information.  Use the name
-	 now to get more information.  */
-      while (__gethostname (tmpbuf->data, tmpbuf->length))
-	if (!scratch_buffer_grow (tmpbuf))
-	  return;
-
-      if ((c = strchr (tmpbuf->data, '.')) != NULL)
-	domain = __strdup (++c);
-      else
-	{
-	  /* We need to preserve the hostname.  */
-	  size_t hstnamelen = strlen (tmpbuf->data) + 1;
-	  while (__gethostbyname_r (tmpbuf->data, &th,
-				    tmpbuf->data + hstnamelen,
-				    tmpbuf->length - hstnamelen,
-				    &h, &herror))
-	    {
-	      if (herror == NETDB_INTERNAL && errno == ERANGE)
-		{
-		  if (!scratch_buffer_grow_preserve (tmpbuf))
-		    return;
-		}
-	      else
-		break;
-	    }
+      domain = __strdup (++c);
+      return domain != NULL;
+    }
 
-	  if (h != NULL && (c = strchr(h->h_name, '.')) != NULL)
-	    domain = __strdup (++c);
-	  else
-	    {
-	      struct in_addr in_addr;
+  /* The name contains no domain information.  Use the name
+     now to get more information.  */
+  while (__gethostname (tmpbuf->data, tmpbuf->length))
+    if (!scratch_buffer_grow (tmpbuf))
+      return false;
 
-	      in_addr.s_addr = htonl (INADDR_LOOPBACK);
+  if ((c = strchr (tmpbuf->data, '.')) != NULL)
+    {
+      domain = __strdup (++c);
+      return domain != NULL;
+    }
 
-	      while (__gethostbyaddr_r ((const char *) &in_addr,
-					sizeof (struct in_addr),
-					AF_INET, &th,
-					tmpbuf->data,
-					tmpbuf->length,
-					&h, &herror))
-		{
-		  if (herror == NETDB_INTERNAL && errno == ERANGE)
-		    {
-		      if (!scratch_buffer_grow (tmpbuf))
-			return;
-		    }
-		  else
-		    break;
-		}
+  /* We need to preserve the hostname.  */
+  size_t hstnamelen = strlen (tmpbuf->data) + 1;
+  while (__gethostbyname_r (tmpbuf->data, &th, tmpbuf->data + hstnamelen,
+			    tmpbuf->length - hstnamelen, &h, &herror))
+    {
+      if (herror == NETDB_INTERNAL && errno == ERANGE)
+	{
+	  if (!scratch_buffer_grow_preserve (tmpbuf))
+	    return false;
+	}
+      else
+	break;
+    }
 
-	      if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
-		domain = __strdup (++c);
-	    }
+  if (h != NULL && (c = strchr(h->h_name, '.')) != NULL)
+    {
+      domain = __strdup (++c);
+      return domain != NULL;
+    }
+
+  struct in_addr in_addr = { .s_addr = htonl (INADDR_LOOPBACK) };
+
+  while (__gethostbyaddr_r ((const char *) &in_addr, sizeof (struct in_addr),
+			    AF_INET, &th, tmpbuf->data, tmpbuf->length, &h,
+			    &herror))
+    {
+      if (herror == NETDB_INTERNAL && errno == ERANGE)
+	{
+	  if (!scratch_buffer_grow (tmpbuf))
+	    return false;
 	}
+      else
+	break;
+    }
+
+  if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
+    {
+      domain = __strdup (++c);
+      return domain != NULL;
     }
+  return true;
 }
 
-static char *
+static bool
 nrl_domainname (void)
 {
   static int not_first;
 
   if (__glibc_likely (atomic_load_acquire (&not_first) != 0))
-    return domain;
+    return true;
+
+  int r = true;
 
   __libc_lock_define_initialized (static, lock);
   __libc_lock_lock (lock);
@@ -180,16 +181,15 @@ nrl_domainname (void)
       struct scratch_buffer tmpbuf;
       scratch_buffer_init (&tmpbuf);
 
-      nrl_domainname_core (&tmpbuf);
+      if ((r = nrl_domainname_core (&tmpbuf)))
+	atomic_store_release (&not_first, 1);
 
       scratch_buffer_free (&tmpbuf);
-
-      atomic_store_release (&not_first, 1);
     }
 
   __libc_lock_unlock (lock);
 
-  return domain;
+  return r;
 };
 
 /* Copy a string to a destination buffer with length checking.  Return
@@ -285,13 +285,17 @@ gni_host_inet_name (struct scratch_buffer *tmpbuf,
 
   if (h)
     {
-      char *c;
-      if ((flags & NI_NOFQDN)
-	  && (c = nrl_domainname ())
-	  && (c = strstr (h->h_name, c))
-	  && (c != h->h_name) && (*(--c) == '.'))
-	/* Terminate the string after the prefix.  */
-	*c = '\0';
+      if (flags & NI_NOFQDN)
+	{
+	  if (!nrl_domainname ())
+	    return EAI_MEMORY;
+
+	  char *c = domain;
+	  if (c != NULL && (c = strstr (h->h_name, c))
+	       && (c != h->h_name) && (*(--c) == '.'))
+	    /* Terminate the string after the prefix.  */
+	    *c = '\0';
+	}
 
       /* If requested, convert from the IDN format.  */
       bool do_idn = flags & NI_IDN;
-- 
2.32.0

Re: [PATCH v2 2/3] inet: Remove strdupa from nrl_domainname()

[DJ Delorie]

Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org> writes:
>        else
>  	{
>  	  /* We need to preserve the hostname.  */
> -	  const char *hstname = strdupa (tmpbuf->data);

Would have copied tmpbuf->data to the stack, and used it..

> -	  while (__gethostbyname_r (hstname, &th,
> -				    tmpbuf->data,
> -				    tmpbuf->length,

> +	  size_t hstnamelen = strlen (tmpbuf->data) + 1;

Count tmpbuf->data, include the trailing NUL.  Ok.

> +	  while (__gethostbyname_r (tmpbuf->data, &th,
> +				    tmpbuf->data + hstnamelen,
> +				    tmpbuf->length - hstnamelen,
>  				    &h, &herror))

But requires more buffer space in tmpbuf->data, so offset.  Ok.

>  	    {
>  	      if (herror == NETDB_INTERNAL && errno == ERANGE)
>  		{
> -		  if (!scratch_buffer_grow (tmpbuf))
> +		  if (!scratch_buffer_grow_preserve (tmpbuf))

This ensures that the hostname in tmpbuf->data is preserved, although it
ALSO preserves the "grown" space if we have to grow twice.  Oh well,
rare.  Ok.

LGTM

Reviewed-by: DJ Delorie <dj@redhat.com>

Re: [PATCH v2 2/3] inet: Remove strdupa from nrl_domainname()

[Adhemerval Zanella]

Ping.

On 10/12/2021 08:07, Adhemerval Zanella wrote:
> We can use the already in place scratch_buffer.
> 
> Checked on x86_64-linux-gnu.
> ---
>  inet/getnameinfo.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
> index 5eee354200..2d2397e7dc 100644
> --- a/inet/getnameinfo.c
> +++ b/inet/getnameinfo.c
> @@ -118,15 +118,15 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
>        else
>  	{
>  	  /* We need to preserve the hostname.  */
> -	  const char *hstname = strdupa (tmpbuf->data);
> -	  while (__gethostbyname_r (hstname, &th,
> -				    tmpbuf->data,
> -				    tmpbuf->length,
> +	  size_t hstnamelen = strlen (tmpbuf->data) + 1;
> +	  while (__gethostbyname_r (tmpbuf->data, &th,
> +				    tmpbuf->data + hstnamelen,
> +				    tmpbuf->length - hstnamelen,
>  				    &h, &herror))
>  	    {
>  	      if (herror == NETDB_INTERNAL && errno == ERANGE)
>  		{
> -		  if (!scratch_buffer_grow (tmpbuf))
> +		  if (!scratch_buffer_grow_preserve (tmpbuf))
>  		    return;
>  		}
>  	      else

[PATCH v2 2/3] inet: Remove strdupa from nrl_domainname()

[Adhemerval Zanella]

We can use the already in place scratch_buffer.

Checked on x86_64-linux-gnu.
---
 inet/getnameinfo.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
index 5eee354200..2d2397e7dc 100644
--- a/inet/getnameinfo.c
+++ b/inet/getnameinfo.c
@@ -118,15 +118,15 @@ nrl_domainname_core (struct scratch_buffer *tmpbuf)
       else
 	{
 	  /* We need to preserve the hostname.  */
-	  const char *hstname = strdupa (tmpbuf->data);
-	  while (__gethostbyname_r (hstname, &th,
-				    tmpbuf->data,
-				    tmpbuf->length,
+	  size_t hstnamelen = strlen (tmpbuf->data) + 1;
+	  while (__gethostbyname_r (tmpbuf->data, &th,
+				    tmpbuf->data + hstnamelen,
+				    tmpbuf->length - hstnamelen,
 				    &h, &herror))
 	    {
 	      if (herror == NETDB_INTERNAL && errno == ERANGE)
 		{
-		  if (!scratch_buffer_grow (tmpbuf))
+		  if (!scratch_buffer_grow_preserve (tmpbuf))
 		    return;
 		}
 	      else
-- 
2.32.0