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Fix mbnambuf support for multi-byte characters. If a substring is larger

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than WIN_CHARS bytes, we shift the suffix (previous substrings) upwards
by the amount this substring exceeds its WIN_CHARS slot.  Profiling shows
this change is indistinguishable from the previous code at 95% confidence.
This bug would result in attempts to access or create files or directories
with multi-byte characters returning an error but no data loss.

Reported and tested by:	avatar
MFC after:	3 days
This commit is contained in:
Nate Lawson 2005-04-16 01:49:50 +00:00
parent d37ed29c98
commit 58ad326be6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=145131
1 changed files with 29 additions and 19 deletions
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48
sys/fs/msdosfs/msdosfs_conv.c
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@ -103,7 +103,7 @@ static u_int16_t unix2winchr(const u_char **, size_t *, int, struct msdosfsmount
static char *nambuf_ptr;
static size_t nambuf_len;
static int nambuf_max_id;
static int nambuf_last_id;
/*
* Convert the unix version of time to dos's idea of time to be used in
@ -1205,33 +1205,43 @@ mbnambuf_init(void)
nambuf_ptr[MAXNAMLEN] = '\0';
}
nambuf_len = 0;
nambuf_max_id = -1;
nambuf_last_id = -1;
}
/*
* Fill out our concatenation buffer with the given substring, at the
* offset specified by its id. For the last substring (i.e., the one with
* the maximum id), use it to calculate the length of the entire string.
* Since this function is usually called with ids in descending order, this
* reduces the number of times we need to call strlen() since we know that
* all previous substrings are exactly WIN_CHARS in length.
* Fill out our concatenation buffer with the given substring, at the offset
* specified by its id. Since this function must be called with ids in
* descending order, we take advantage of the fact that ASCII substrings are
* exactly WIN_CHARS in length. For non-ASCII substrings, we shift all
* previous (i.e. higher id) substrings upwards to make room for this one.
* This only penalizes portions of substrings that contain more than
* WIN_CHARS bytes when they are first encountered.
*/
void
mbnambuf_write(char *name, int id)
{
size_t count;
char *slot;
count = WIN_CHARS;
if (id > nambuf_max_id) {
count = strlen(name);
nambuf_len = id * WIN_CHARS + count;
if (nambuf_len > MAXNAMLEN) {
printf("msdosfs: file name %zu too long\n", nambuf_len);
return;
}
nambuf_max_id = id;
KASSERT(nambuf_len == 0 || id == nambuf_last_id - 1,
("non-decreasing id, id %d last id %d", id, nambuf_last_id));
/* Store this substring in a WIN_CHAR-aligned slot. */
slot = nambuf_ptr + (id * WIN_CHARS);
count = strlen(name);
if (nambuf_len + count > MAXNAMLEN) {
printf("msdosfs: file name %zu too long\n", nambuf_len + count);
return;
}
memcpy(nambuf_ptr + (id * WIN_CHARS), name, count);
/* Shift suffix upwards by the amount length exceeds WIN_CHARS. */
if (count > WIN_CHARS && nambuf_len != 0)
bcopy(slot + WIN_CHARS, slot + count, nambuf_len);
/* Copy in the substring to its slot and update length so far. */
bcopy(name, slot, count);
nambuf_len += count;
nambuf_last_id = id;
}
/*
@ -1249,7 +1259,7 @@ mbnambuf_flush(struct dirent *dp)
mbnambuf_init();
return (NULL);
}
memcpy(dp->d_name, nambuf_ptr, nambuf_len);
bcopy(nambuf_ptr, dp->d_name, nambuf_len);
dp->d_name[nambuf_len] = '\0';
dp->d_namlen = nambuf_len;