In function create_long_filname(), the array name[8 + 3] in
struct direntry_t is used as if it were defined as name[32].
This is intentional and works. It's nevertheless an out of
bounds array access. To avoid this problem, this patch adds a
struct lfn_direntry_t with multiple name arrays. A directory
entry for a long FAT file name is significantly different from
a directory entry for a regular FAT file name.
This change makes whole logic dealing with the long filenames
a bit more clear (hopefully).
Based on ideas by Volker Rümelin.
Signed-off-by: Michael Tokarev <m...@tls.msk.ru>
---
block/vvfat.c | 69 ++++++++++++++++++++++++++++++++-------------------
1 file changed, 43 insertions(+), 26 deletions(-)
diff --git a/block/vvfat.c b/block/vvfat.c
index 8ffe8b3b9b..8320733045 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -255,6 +255,17 @@ typedef struct direntry_t {
uint32_t size;
} QEMU_PACKED direntry_t;
+typedef struct lfn_direntry_t {
+ uint8_t sequence;
+ uint8_t name01[10];
+ uint8_t attributes;
+ uint8_t direntry_type;
+ uint8_t sfn_checksum;
+ uint8_t name0e[12];
+ uint16_t begin;
+ uint8_t name1c[4];
+} QEMU_PACKED lfn_direntry_t;
+
/* this structure are used to transparently access the files */
typedef struct mapping_t {
@@ -399,11 +410,22 @@ static void init_mbr(BDRVVVFATState *s, int cyls, int
heads, int secs)
/* direntry functions */
+static unsigned write_lfn_part(uint8_t *dest, unsigned dsize,
+ const gunichar2 *lptr, const gunichar2 *lend)
+{
+ unsigned i;
+ for(i = 0; i < dsize / 2 && lptr + i < lend; ++i) {
+ dest[i / 2 + 0] = lptr[i] & 0xff;
+ dest[i / 2 + 1] = lptr[i] >> 8;
+ }
+ return i; /* return number of elements actually written */
+}
+
static direntry_t *create_long_filename(BDRVVVFATState *s, const char
*filename)
{
- int number_of_entries, i;
+ unsigned number_of_entries, entidx;
+ gunichar2 *lptr, *lend;
glong length;
- direntry_t *entry;
gunichar2 *longname = g_utf8_to_utf16(filename, -1, NULL, &length, NULL);
if (!longname) {
@@ -411,31 +433,26 @@ static direntry_t *create_long_filename(BDRVVVFATState
*s, const char *filename)
return NULL;
}
- number_of_entries = DIV_ROUND_UP(length * 2, 26);
-
- for(i=0;i<number_of_entries;i++) {
- entry=array_get_next(&(s->directory));
- entry->attributes=0xf;
- entry->reserved[0]=0;
- entry->begin=0;
- entry->name[0]=(number_of_entries-i)|(i==0?0x40:0);
- }
- for(i=0;i<26*number_of_entries;i++) {
- int offset=(i%26);
- if(offset<10) offset=1+offset;
- else if(offset<22) offset=14+offset-10;
- else offset=28+offset-22;
- entry=array_get(&(s->directory),s->directory.next-1-(i/26));
- if (i >= 2 * length + 2) {
- entry->name[offset] = 0xff;
- } else if (i % 2 == 0) {
- entry->name[offset] = longname[i / 2] & 0xff;
- } else {
- entry->name[offset] = longname[i / 2] >> 8;
- }
+ /*
+ * each lfn_direntry holds 13 utf16 chars (26 bytes) of the file name,
+ * the name is split into several directory entries.
+ */
+ number_of_entries = DIV_ROUND_UP(length, 13);
+
+ lend = longname + length; /* pointer past the end of longname */
+ for(entidx = 0, lptr = longname; entidx < number_of_entries; entidx++) {
+ lfn_direntry_t *entry = array_get_next(&(s->directory));
+ entry->sequence = (number_of_entries - entidx) | (entidx == 0 ? 0x40 :
0);
+ entry->attributes = 0xf;
+ entry->direntry_type = 0;
+ entry->begin = 0;
+ /* each lftn_direntry has 3 pieces to hold parts of long file name */
+ lptr += write_lfn_part(entry->name01, sizeof(entry->name01), lptr,
lend);
+ lptr += write_lfn_part(entry->name0e, sizeof(entry->name0e), lptr,
lend);
+ lptr += write_lfn_part(entry->name1c, sizeof(entry->name1c), lptr,
lend);
}
g_free(longname);
- return array_get(&(s->directory),s->directory.next-number_of_entries);
+ return array_get(&(s->directory), s->directory.next - number_of_entries);
}
static char is_free(const direntry_t* direntry)
@@ -731,7 +748,7 @@ static inline direntry_t*
create_short_and_long_name(BDRVVVFATState* s,
/* calculate anew, because realloc could have taken place */
entry_long=array_get(&(s->directory),long_index);
while(entry_long<entry && is_long_name(entry_long)) {
- entry_long->reserved[1]=chksum;
+ ((lfn_direntry_t *)entry_long)->sfn_checksum = chksum;
entry_long++;
}
}
--
2.39.5
