OGAWA Hirofumi wrote:
>
> Andrew Morton <akpm@zip.com.au> writes:
>
> > > Additional check on the number of followed links could be useful there.
> > > No chain should be longer than the number of clusters on the fs.
> > > Although on large FAT32 filesystems the number of clusters can be high,
> > > a very long loop is still better than an infinite one. (In cases where
> > > we know the file size, this limit can be reduced to
> > > file_size/cluster_size + 1 links).
> >
> > hmm.. OK, I'll take a look at that approach.
>
> The maximum number of directory entries is 65536 in ordinarily. The
> following patch prevents the infinite loop of a directory (include the
> limit to added directory).
>
> I think the following patch is a bit useful.
Ah lovely. I was looking for your email address when this came up,
but couldn't find it.
Here's the 2.4.18-pre3 version of your patch. I've tested it against
the corrupted filesystem image and it works fine:
Jan 14 02:40:50 mnm kernel: FAT: Filesystem panic (dev 07:00)
Jan 14 02:40:50 mnm kernel: Directory 3329: exceeded the maximum size of directory
Jan 14 02:40:50 mnm kernel: File system has been set read-only
Jan 14 02:40:50 mnm kernel: FAT: Filesystem panic (dev 07:00)
Jan 14 02:40:50 mnm kernel: Directory 5: exceeded the maximum size of directory
If you're satisfied that everything is OK, I'd suggest that you
send the diff to Marcelo.
Thanks.
--- linux-2.4.18-pre3/fs/fat/dir.c Fri Oct 12 13:48:42 2001
+++ linux-akpm/fs/fat/dir.c Mon Jan 14 02:31:49 2002
@@ -727,7 +727,13 @@ int fat_add_entries(struct inode *dir,in
offset = curr = 0;
*bh = NULL;
row = 0;
- while (fat_get_entry(dir,&curr,bh,de,ino) > -1) {
+ while (fat_get_entry(dir, &curr, bh, de, ino) > -1) {
+ /* check the maximum size of directory */
+ if (curr >= FAT_MAX_DIR_SIZE) {
+ fat_brelse(sb, *bh);
+ return -ENOSPC;
+ }
+
if (IS_FREE((*de)->name)) {
if (++row == slots)
return offset;
@@ -742,7 +748,10 @@ int fat_add_entries(struct inode *dir,in
if (!new_bh)
return -ENOSPC;
fat_brelse(sb, new_bh);
- do fat_get_entry(dir,&curr,bh,de,ino); while (++row<slots);
+ do {
+ fat_get_entry(dir, &curr, bh, de, ino);
+ } while (++row < slots);
+
return offset;
}
--- linux-2.4.18-pre3/fs/fat/inode.c Thu Nov 22 23:02:58 2001
+++ linux-akpm/fs/fat/inode.c Mon Jan 14 02:31:49 2002
@@ -372,11 +372,37 @@ out:
return ret;
}
+static void fat_calc_dir_size(struct inode *inode)
+{
+ struct super_block *sb = inode->i_sb;
+ int nr;
+
+ inode->i_size = 0;
+ if (MSDOS_I(inode)->i_start == 0)
+ return;
+
+ nr = MSDOS_I(inode)->i_start;
+ do {
+ inode->i_size += 1 << MSDOS_SB(sb)->cluster_bits;
+ if (!(nr = fat_access(sb, nr, -1))) {
+ printk("FAT: Directory %ld: bad FAT\n",
+ inode->i_ino);
+ break;
+ }
+ if (inode->i_size > FAT_MAX_DIR_SIZE) {
+ fat_fs_panic(sb, "Directory %ld: "
+ "exceeded the maximum size of directory",
+ inode->i_ino);
+ inode->i_size = FAT_MAX_DIR_SIZE;
+ break;
+ }
+ } while (nr != -1);
+}
+
static void fat_read_root(struct inode *inode)
{
struct super_block *sb = inode->i_sb;
struct msdos_sb_info *sbi = MSDOS_SB(sb);
- int nr;
INIT_LIST_HEAD(&MSDOS_I(inode)->i_fat_hash);
MSDOS_I(inode)->i_location = 0;
@@ -390,16 +416,7 @@ static void fat_read_root(struct inode *
inode->i_fop = &fat_dir_operations;
if (sbi->fat_bits == 32) {
MSDOS_I(inode)->i_start = sbi->root_cluster;
- if ((nr = MSDOS_I(inode)->i_start) != 0) {
- while (nr != -1) {
- inode->i_size += 1 << sbi->cluster_bits;
- if (!(nr = fat_access(sb, nr, -1))) {
- printk("Directory %ld: bad FAT\n",
- inode->i_ino);
- break;
- }
- }
- }
+ fat_calc_dir_size(inode);
} else {
MSDOS_I(inode)->i_start = 0;
inode->i_size = sbi->dir_entries * sizeof(struct msdos_dir_entry);
@@ -885,7 +902,6 @@ static void fat_fill_inode(struct inode
{
struct super_block *sb = inode->i_sb;
struct msdos_sb_info *sbi = MSDOS_SB(sb);
- int nr;
INIT_LIST_HEAD(&MSDOS_I(inode)->i_fat_hash);
MSDOS_I(inode)->i_location = 0;
@@ -916,15 +932,7 @@ static void fat_fill_inode(struct inode
inode->i_nlink = 1;
}
#endif
- if ((nr = MSDOS_I(inode)->i_start) != 0)
- while (nr != -1) {
- inode->i_size += 1 << sbi->cluster_bits;
- if (!(nr = fat_access(sb, nr, -1))) {
- printk("Directory %ld: bad FAT\n",
- inode->i_ino);
- break;
- }
- }
+ fat_calc_dir_size(inode);
MSDOS_I(inode)->mmu_private = inode->i_size;
} else { /* not a directory */
inode->i_generation |= 1;
--- linux-2.4.18-pre3/fs/fat/misc.c Fri Oct 12 13:48:42 2001
+++ linux-akpm/fs/fat/misc.c Mon Jan 14 02:33:45 2002
@@ -38,15 +38,24 @@ static char ascii_extensions[] =
* read-only. The file system can be made writable again by remounting it.
*/
-void fat_fs_panic(struct super_block *s,const char *msg)
+static char panic_msg[512];
+
+void fat_fs_panic(struct super_block *s,const char *fmt, ...)
{
int not_ro;
+ va_list args;
+
+ va_start (args, fmt);
+ vsnprintf (panic_msg, sizeof(panic_msg), fmt, args);
+ va_end (args);
not_ro = !(s->s_flags & MS_RDONLY);
- if (not_ro) s->s_flags |= MS_RDONLY;
- printk("Filesystem panic (dev %s).\n %s\n", kdevname(s->s_dev), msg);
if (not_ro)
- printk(" File system has been set read-only\n");
+ s->s_flags |= MS_RDONLY;
+ printk("FAT: Filesystem panic (dev %s)\n"
+ " %s\n", kdevname(s->s_dev), panic_msg);
+ if (not_ro)
+ printk(" File system has been set read-only\n");
}
@@ -472,11 +481,13 @@ static int raw_scan_nonroot(struct super
int *number,int *ino,struct buffer_head **res_bh,struct msdos_dir_entry
**res_de)
{
- int count,cluster;
+ int count, cluster;
+ unsigned long dir_size;
#ifdef DEBUG
printk("raw_scan_nonroot: start=%d\n",start);
#endif
+ dir_size = 0;
do {
for (count = 0; count < MSDOS_SB(sb)->cluster_size; count++) {
if ((cluster = raw_scan_sector(sb,(start-2)*
@@ -484,6 +495,13 @@ static int raw_scan_nonroot(struct super
count,name,number,ino,res_bh,res_de)) >= 0)
return cluster;
}
+ dir_size += 1 << MSDOS_SB(sb)->cluster_bits;
+ if (dir_size > FAT_MAX_DIR_SIZE) {
+ fat_fs_panic(sb, "Directory %d: "
+ "exceeded the maximum size of directory",
+ start);
+ break;
+ }
if (!(start = fat_access(sb,start,-1))) {
fat_fs_panic(sb,"FAT error");
break;
@@ -491,8 +509,8 @@ static int raw_scan_nonroot(struct super
#ifdef DEBUG
printk("next start: %d\n",start);
#endif
- }
- while (start != -1);
+ } while (start != -1);
+
return -ENOENT;
}
--- linux-2.4.18-pre3/include/linux/msdos_fs.h Fri Oct 12 13:48:42 2001
+++ linux-akpm/include/linux/msdos_fs.h Mon Jan 14 02:31:49 2002
@@ -19,6 +19,10 @@
#define MSDOS_DPS_BITS 4 /* log2(MSDOS_DPS) */
#define MSDOS_DIR_BITS 5 /* log2(sizeof(struct msdos_dir_entry)) */
+/* directory limit */
+#define FAT_MAX_DIR_ENTRIES (65536)
+#define FAT_MAX_DIR_SIZE (FAT_MAX_DIR_ENTRIES << MSDOS_DIR_BITS)
+
#define MSDOS_SUPER_MAGIC 0x4d44 /* MD */
#define FAT_CACHE 8 /* FAT cache size */
@@ -297,7 +301,7 @@ extern void fat_write_inode(struct inode
extern int fat_notify_change(struct dentry * dentry, struct iattr * attr);
/* fat/misc.c */
-extern void fat_fs_panic(struct super_block *s, const char *msg);
+extern void fat_fs_panic(struct super_block *s, const char *fmt, ...);
extern int fat_is_binary(char conversion, char *extension);
extern void lock_fat(struct super_block *sb);
extern void unlock_fat(struct super_block *sb);
-
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This archive was generated by hypermail 2b29 : Tue Jan 15 2002 - 21:00:44 EST