Re: [PATCH 2/4] Return better error codes from vfat_valid_longname()

From: Rene Scharfe
Date: Tue Nov 09 2004 - 11:50:40 EST


OGAWA Hirofumi wrote:
> lsr@xxxxxxxxxxxxxxxxxxxxxxx writes:
>
>
>>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.).
>
>
> Yes, the error code for this should be consistent on _system_.
> Until we do it, this change would not be useful.

At least ENAMETOOLONG and ENOENT are properly defined error codes. :)

VFAT returning EACCES when trying to access "forbidden" filenames would
be useful right now because it gives better error messages with current
tools. At least the error msg of touch looks less confusing IMHO
(didn't check much other programs).

And I doubt we'll get an official Linux error code for invalid
filenames soon: according to POSIX there are only two forbidden
characters, '/' and '\0', so anything goes.

Anyway, what do you think about the following patch? I just replaced
EACCES by EINVAL.

Thanks,
René



--- ./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 -EINVAL;

/* 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 -EINVAL;
}
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 -EINVAL;
}
}

/* check for invalid characters */
for (p = name; p < name + len; p++) {
if (*p < 0x0020 || strchr("*?<>|\":\\", *p) != NULL)
- return 0;
+ return -EINVAL;
}

- 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;
-
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