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(wip) Safely wrap memory access from File. 

Previously we had a lot of places where &uxn.ram[addr] was being used without
checking that addr+length < 65536. In cases where that value is exceeded, the
reads/writes should wrap back around to the beginning of memory.

After this change, most of the accesses have been made safe.

Two places that are not (yet) converted:

 1. file_init: We already truncate reads past the end of ram.
 While this does is technically incorrect it will avoid memory
 corruption or crashing.

 2. file_read_dir: The code here still uses snprintf formatting.
This commit is contained in:
~d6 2024-09-19 23:08:00 -04:00
parent df51651789
commit 7fcd7ad635
1 changed files with 49 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
src/devices/file.c
View File

@ -195,7 +195,20 @@ file_init(UxnFile *c, char *filename, size_t max_len, int override_sandbox)
}
static Uint16
file_read(UxnFile *c, void *dest, int len)
file_read_file(Uint16 addr, int len, FILE *f)
{
int total = addr + len;
if (total < 0x10000) {
return fread(&uxn.ram[addr], 1, len, f);
} else {
size_t n1 = fread(&uxn.ram[addr], 1, 0x10000 - addr, f);
size_t n2 = fread(&uxn.ram[0], 1, total - 0x10000, f);
return n1 + n2;
}
}
static Uint16
file_read(UxnFile *c, Uint16 addr, int len)
{
if(c->outside_sandbox) return 0;
if(c->state != FILE_READ && c->state != DIR_READ) {
@ -206,9 +219,9 @@ file_read(UxnFile *c, void *dest, int len)
c->state = FILE_READ;
}
if(c->state == FILE_READ)
return fread(dest, 1, len, c->f);
return file_read_file(addr, len, c->f);
if(c->state == DIR_READ)
return file_read_dir(c, dest, len);
return file_read_dir(c, (char *)&uxn.ram[addr], len);
return 0;
}
@ -245,7 +258,21 @@ ensure_parent_dirs(char *p)
}
static Uint16
file_write(UxnFile *c, void *src, Uint16 len, Uint8 flags)
file_write_file(Uint16 addr, int len, FILE *f)
{
int total = addr + len;
if (total < 0x10000) {
Uint16 n = fwrite(&uxn.ram[addr], 1, len, f);
return fflush(f) == 0 ? n : 0;
} else {
Uint16 n1 = fwrite(&uxn.ram[addr], 1, 0x10000 - addr, f);
Uint16 n2 = fwrite(&uxn.ram[0], 1, total - 0x10000, f);
return fflush(f) == 0 ? n1 + n2 : 0;
}
}
static Uint16
file_write(UxnFile *c, Uint16 addr, Uint16 len, Uint8 flags)
{
Uint16 ret = 0;
if(c->outside_sandbox) return 0;
@ -258,8 +285,7 @@ file_write(UxnFile *c, void *src, Uint16 len, Uint8 flags)
c->state = FILE_WRITE;
}
if(c->state == FILE_WRITE) {
if((ret = fwrite(src, 1, len, c->f)) > 0 && fflush(c->f) != 0)
ret = 0;
ret = file_write_file(addr, len, c->f);
}
if (c->state == DIR_WRITE) {
ret = dir_exists(c->current_filename);
@ -268,38 +294,38 @@ file_write(UxnFile *c, void *src, Uint16 len, Uint8 flags)
}
static Uint16
stat_fill(Uint8 *dest, Uint16 len, char c)
stat_fill(Uint16 addr, Uint16 len, char c)
{
Uint16 i;
for (i = 0; i < len; i++)
*(dest++) = c;
uxn.ram[(addr + i) & 0xffff] = c;
return len;
}
static Uint16
stat_size(Uint8 *dest, Uint16 len, off_t size)
stat_size(Uint16 addr, Uint16 len, off_t size)
{
Uint16 i;
dest += len - 1;
for (i = 0; i < len; i++) {
*(dest--) = '0' + (Uint8)(size & 0xf);
for (i = 1; i <= len; i++) {
char c = '0' + (Uint8)(size & 0xf);
uxn.ram[(addr + len - i) & 0xffff] = c;
size = size >> 4;
}
return size == 0 ? len : stat_fill(dest, len, '?');
return size == 0 ? len : stat_fill(addr, len, '?');
}
static Uint16
file_stat(UxnFile *c, void *dest, Uint16 len)
file_stat(UxnFile *c, Uint16 addr, Uint16 len)
{
struct stat st;
if(c->outside_sandbox)
return 0;
else if(stat(c->current_filename, &st))
return stat_fill(dest, len, '!');
return stat_fill(addr, len, '!');
else if(S_ISDIR(st.st_mode))
return stat_fill(dest, len, '-');
return stat_fill(addr, len, '-');
else
return stat_size(dest, len, st.st_size);
return stat_size(addr, len, st.st_size);
}
static Uint16
@ -320,7 +346,7 @@ file_deo(Uint8 port)
len = PEEK2(&uxn.dev[0xaa]);
if(len > 0x10000 - addr)
len = 0x10000 - addr;
res = file_stat(&uxn_file[0], &uxn.ram[addr], len);
res = file_stat(&uxn_file[0], addr, len);
POKE2(&uxn.dev[0xa2], res);
break;
case 0xa6:
@ -337,7 +363,7 @@ file_deo(Uint8 port)
len = PEEK2(&uxn.dev[0xaa]);
if(len > 0x10000 - addr)
len = 0x10000 - addr;
res = file_read(&uxn_file[0], &uxn.ram[addr], len);
res = file_read(&uxn_file[0], addr, len);
POKE2(&uxn.dev[0xa2], res);
break;
case 0xaf:
@ -345,7 +371,7 @@ file_deo(Uint8 port)
len = PEEK2(&uxn.dev[0xaa]);
if(len > 0x10000 - addr)
len = 0x10000 - addr;
res = file_write(&uxn_file[0], &uxn.ram[addr], len, uxn.dev[0xa7]);
res = file_write(&uxn_file[0], addr, len, uxn.dev[0xa7]);
POKE2(&uxn.dev[0xa2], res);
break;
/* File 2 */
@ -354,7 +380,7 @@ file_deo(Uint8 port)
len = PEEK2(&uxn.dev[0xba]);
if(len > 0x10000 - addr)
len = 0x10000 - addr;
res = file_stat(&uxn_file[1], &uxn.ram[addr], len);
res = file_stat(&uxn_file[1], addr, len);
POKE2(&uxn.dev[0xb2], res);
break;
case 0xb6:
@ -371,7 +397,7 @@ file_deo(Uint8 port)
len = PEEK2(&uxn.dev[0xba]);
if(len > 0x10000 - addr)
len = 0x10000 - addr;
res = file_read(&uxn_file[1], &uxn.ram[addr], len);
res = file_read(&uxn_file[1], addr, len);
POKE2(&uxn.dev[0xb2], res);
break;
case 0xbf:
@ -379,7 +405,7 @@ file_deo(Uint8 port)
len = PEEK2(&uxn.dev[0xba]);
if(len > 0x10000 - addr)
len = 0x10000 - addr;
res = file_write(&uxn_file[1], &uxn.ram[addr], len, uxn.dev[0xb7]);
res = file_write(&uxn_file[1], addr, len, uxn.dev[0xb7]);
POKE2(&uxn.dev[0xb2], res);
break;
}