Re: [PATCH] include/cygwin/limits.h: add XATTR_{NAME,SIZE,LIST}_MAX

[Philippe Cerfon <philcerf@gmail.com>]

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Hey Corinna.

On Wed, Jun 7, 2023 at 12:06 PM Corinna Vinschen
<corinna-cygwin@cygwin.com> wrote:
> Hmm, the comparisons would have to check for XATTR_NAME_MAX anyway,
> so maybe inlining is cleaner in this case.

Please have a look at the updated and attached patches.

Thanks,
Philippe.

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From 82e2ff6f52d7401210247ae396ce3f1f115d93f0 Mon Sep 17 00:00:00 2001
From: Philippe Cerfon <philcerf@gmail.com>
Date: Tue, 30 May 2023 13:16:18 +0200
Subject: [PATCH 1/2] Cygwin: export XATTR_{NAME,SIZE,LIST}_MAX

These are used for example by CPython.

Signed-off-by: Philippe Cerfon <philcerf@gmail.com>
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
---
 winsup/cygwin/include/cygwin/limits.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/winsup/cygwin/include/cygwin/limits.h b/winsup/cygwin/include/cygwin/limits.h
index aefc7c7bd..ea3e2836a 100644
--- a/winsup/cygwin/include/cygwin/limits.h
+++ b/winsup/cygwin/include/cygwin/limits.h
@@ -56,4 +56,11 @@ details. */
 #define __PATH_MAX 4096
 #define __PIPE_BUF 4096
 
+/* XATTR_NAME_MAX is the maximum XATTR name length excluding the null
+ * terminator. Since only XATTRs in the `user' namespace are allowed and the
+ * `user.' prefix is not stored, the maximum is increased by 5. */
+#define XATTR_NAME_MAX 260
+#define XATTR_SIZE_MAX 65536
+#define XATTR_LIST_MAX 65536
+
 #endif /* _CYGWIN_LIMITS_H__ */
-- 
2.40.1


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From 34a2e210082ddbf87d2c9569b6b14775a6cc5b95 Mon Sep 17 00:00:00 2001
From: Philippe Cerfon <philcerf@gmail.com>
Date: Tue, 6 Jun 2023 02:52:49 +0200
Subject: [PATCH 2/2] Cygwin: use new XATTR_{NAME,SIZE}_MAX instead of
 MAX_EA_{NAME,VALUE}_LEN

Signed-off-by: Philippe Cerfon <philcerf@gmail.com>
---
 winsup/cygwin/ntea.cc | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/winsup/cygwin/ntea.cc b/winsup/cygwin/ntea.cc
index a400fcb2b..ef1fdf4cc 100644
--- a/winsup/cygwin/ntea.cc
+++ b/winsup/cygwin/ntea.cc
@@ -17,9 +17,7 @@ details. */
 #include "tls_pbuf.h"
 #include <stdlib.h>
 #include <attr/xattr.h>
-
-#define MAX_EA_NAME_LEN    256
-#define MAX_EA_VALUE_LEN 65536
+#include <cygwin/limits.h>
 
 /* At least one maximum sized entry fits.
    CV 2014-04-04: NtQueryEaFile function chokes on buffers bigger than 64K
@@ -27,13 +25,14 @@ details. */
 		  on a remote share, at least on Windows 7 and later.
 		  In theory the buffer should have a size of
 
-		    sizeof (FILE_FULL_EA_INFORMATION) + MAX_EA_NAME_LEN
-		    + MAX_EA_VALUE_LEN
+		    sizeof (FILE_FULL_EA_INFORMATION)
+		    + (XATTR_NAME_MAX + 1 - strlen("user."))
+		    + XATTR_SIZE_MAX
 
 		  (65804 bytes), but we're opting for simplicity here, and
 		  a 64K buffer has the advantage that we can use a tmp_pathbuf
 		  buffer, rather than having to alloca 64K from stack. */
-#define EA_BUFSIZ MAX_EA_VALUE_LEN
+#define EA_BUFSIZ XATTR_SIZE_MAX
 
 #define NEXT_FEA(p) ((PFILE_FULL_EA_INFORMATION) (p->NextEntryOffset \
 		     ? (char *) p + p->NextEntryOffset : NULL))
@@ -55,7 +54,7 @@ read_ea (HANDLE hdl, path_conv &pc, const char *name, char *value, size_t size)
      returns the last EA entry of the file infinitely.  Even utilizing the
      optional EaIndex only helps marginally.  If you use that, the last
      EA in the file is returned twice. */
-  char lastname[MAX_EA_NAME_LEN];
+  char lastname[(XATTR_NAME_MAX + 1 - strlen("user."))];
 
   __try
     {
@@ -95,7 +94,7 @@ read_ea (HANDLE hdl, path_conv &pc, const char *name, char *value, size_t size)
 	      __leave;
 	    }
 
-	  if ((nlen = strlen (name)) >= MAX_EA_NAME_LEN)
+	  if ((nlen = strlen (name)) >= (XATTR_NAME_MAX + 1 - strlen("user.")))
 	    {
 	      set_errno (EINVAL);
 	      __leave;
@@ -197,7 +196,7 @@ read_ea (HANDLE hdl, path_conv &pc, const char *name, char *value, size_t size)
 		  /* For compatibility with Linux, we always prepend "user." to
 		     the attribute name, so effectively we only support user
 		     attributes from a application point of view. */
-		  char tmpbuf[MAX_EA_NAME_LEN * 2];
+		  char tmpbuf[(XATTR_NAME_MAX + 1 - strlen("user.")) * 2];
 		  char *tp = stpcpy (tmpbuf, "user.");
 		  stpcpy (tp, fea->EaName);
 		  /* NTFS stores all EA names in uppercase unfortunately.  To
@@ -297,7 +296,7 @@ write_ea (HANDLE hdl, path_conv &pc, const char *name, const char *value,
       /* Skip "user." prefix. */
       name += 5;
 
-      if ((nlen = strlen (name)) >= MAX_EA_NAME_LEN)
+      if ((nlen = strlen (name)) >= (XATTR_NAME_MAX + 1 - strlen("user.")))
 	{
 	  set_errno (EINVAL);
 	  __leave;
-- 
2.40.1