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Date: Tue, 9 Nov 2004 02:38:48 +0100
From: lsr@neapel230.server4you.de
To: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH 2/4] Return better error codes from vfat_valid_longname()
Message-ID: <20041109013848.GC6835@neapel230.server4you.de>
References: <41901DD1.mail5VX1GOOYK@lsrfire.ath.cx>
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Currently vfat returns -EINVAL if one tries to create a file or directory
with an invalid name. This patch changes vfat_valid_longname() to return
a more specific error code.

POSIX doesn't define a nice error code for invalid filenames, so I chose
EACCES -- unlike EINVAL this is a valid error code of mkdir(2). Hope it
sort of fits. (EINVAL did *not* fit; it generally seems to point to
problems not with the filename  but with e.g. the flags value of open(2)
etc.).

As a result file utilities give more meaningful error messages. Example:

	before $ touch nul
	touch: setting times of `nul': No such file or directory

	after $ touch nul
	touch: cannot touch `nul': Permission denied

--- ./fs/vfat/namei.c.orig	2004-11-08 21:33:35.000000000 +0100
+++ ./fs/vfat/namei.c	2004-11-08 21:32:52.000000000 +0100
@@ -184,10 +184,13 @@ static int vfat_valid_longname(const uns
 {
 	const unsigned char *p;
 
-	if (len && name[len-1] == ' ')
-		return 0;
-	if (len >= 256)
-		return 0;
+	if (len == 0)
+		return -ENOENT;
+	if (len > 255)
+		return -ENAMETOOLONG;
+
+	if (name[len-1] == ' ')
+		return -EACCES;
 
 	/* MS-DOS "device special files" */
 	if (len == 3 || (len > 3 && name[3] == '.')) {	/* basename == 3 */
@@ -195,24 +198,24 @@ static int vfat_valid_longname(const uns
 		    !strnicmp(name, "con", 3) ||
 		    !strnicmp(name, "nul", 3) ||
 		    !strnicmp(name, "prn", 3))
-			return 0;
+			return -EACCES;
 	}
 	if (len == 4 || (len > 4 && name[4] == '.')) {	/* basename == 4 */
 		/* "com1", "com2", ... */
 		if ('1' <= name[3] && name[3] <= '9') {
 			if (!strnicmp(name, "com", 3) ||
 			    !strnicmp(name, "lpt", 3))
-				return 0;
+				return -EACCES;
 		}
 	}
 
 	/* check for invalid characters */
 	for (p = name; p < name + len; p++) {
 		if (*p < 0x0020 || strchr("*?<>|\":\\", *p) != NULL)
-			return 0;
+			return -EACCES;
 	}
 
-	return 1;
+	return 0;
 }
 
 static int vfat_find_form(struct inode *dir, unsigned char *name)
@@ -615,8 +618,9 @@ static int vfat_build_slots(struct inode
 	loff_t offset;
 
 	*slots = 0;
-	if (!vfat_valid_longname(name, len))
-		return -EINVAL;
+	res = vfat_valid_longname(name, len);
+	if (res)
+		return res;
 
 	if(!(page = __get_free_page(GFP_KERNEL)))
 		return -ENOMEM;