linux/fs/isofs/namei.c
Jan Kara 2deb1acc65 isofs: fix access to unallocated memory when reading corrupted filesystem
When a directory on isofs is corrupted, we did not check whether length of the
name in a directory entry and the length of the directory entry itself are
consistent.  This could lead to possible access beyond the end of buffer when
the length of the name was too big.  Add this sanity check to directory
reading code.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 08:29:33 -07:00

196 lines
4.4 KiB
C

/*
* linux/fs/isofs/namei.c
*
* (C) 1992 Eric Youngdale Modified for ISO 9660 filesystem.
*
* (C) 1991 Linus Torvalds - minix filesystem
*/
#include <linux/smp_lock.h>
#include "isofs.h"
/*
* ok, we cannot use strncmp, as the name is not in our data space.
* Thus we'll have to use isofs_match. No big problem. Match also makes
* some sanity tests.
*/
static int
isofs_cmp(struct dentry *dentry, const char *compare, int dlen)
{
struct qstr qstr;
if (!compare)
return 1;
/* check special "." and ".." files */
if (dlen == 1) {
/* "." */
if (compare[0] == 0) {
if (!dentry->d_name.len)
return 0;
compare = ".";
} else if (compare[0] == 1) {
compare = "..";
dlen = 2;
}
}
qstr.name = compare;
qstr.len = dlen;
return dentry->d_op->d_compare(dentry, &dentry->d_name, &qstr);
}
/*
* isofs_find_entry()
*
* finds an entry in the specified directory with the wanted name. It
* returns the inode number of the found entry, or 0 on error.
*/
static unsigned long
isofs_find_entry(struct inode *dir, struct dentry *dentry,
unsigned long *block_rv, unsigned long *offset_rv,
char *tmpname, struct iso_directory_record *tmpde)
{
unsigned long bufsize = ISOFS_BUFFER_SIZE(dir);
unsigned char bufbits = ISOFS_BUFFER_BITS(dir);
unsigned long block, f_pos, offset, block_saved, offset_saved;
struct buffer_head *bh = NULL;
struct isofs_sb_info *sbi = ISOFS_SB(dir->i_sb);
if (!ISOFS_I(dir)->i_first_extent)
return 0;
f_pos = 0;
offset = 0;
block = 0;
while (f_pos < dir->i_size) {
struct iso_directory_record *de;
int de_len, match, i, dlen;
char *dpnt;
if (!bh) {
bh = isofs_bread(dir, block);
if (!bh)
return 0;
}
de = (struct iso_directory_record *) (bh->b_data + offset);
de_len = *(unsigned char *) de;
if (!de_len) {
brelse(bh);
bh = NULL;
f_pos = (f_pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1);
block = f_pos >> bufbits;
offset = 0;
continue;
}
block_saved = bh->b_blocknr;
offset_saved = offset;
offset += de_len;
f_pos += de_len;
/* Make sure we have a full directory entry */
if (offset >= bufsize) {
int slop = bufsize - offset + de_len;
memcpy(tmpde, de, slop);
offset &= bufsize - 1;
block++;
brelse(bh);
bh = NULL;
if (offset) {
bh = isofs_bread(dir, block);
if (!bh)
return 0;
memcpy((void *) tmpde + slop, bh->b_data, offset);
}
de = tmpde;
}
dlen = de->name_len[0];
dpnt = de->name;
/* Basic sanity check, whether name doesn't exceed dir entry */
if (de_len < dlen + sizeof(struct iso_directory_record)) {
printk(KERN_NOTICE "iso9660: Corrupted directory entry"
" in block %lu of inode %lu\n", block,
dir->i_ino);
return 0;
}
if (sbi->s_rock &&
((i = get_rock_ridge_filename(de, tmpname, dir)))) {
dlen = i; /* possibly -1 */
dpnt = tmpname;
#ifdef CONFIG_JOLIET
} else if (sbi->s_joliet_level) {
dlen = get_joliet_filename(de, tmpname, dir);
dpnt = tmpname;
#endif
} else if (sbi->s_mapping == 'a') {
dlen = get_acorn_filename(de, tmpname, dir);
dpnt = tmpname;
} else if (sbi->s_mapping == 'n') {
dlen = isofs_name_translate(de, tmpname, dir);
dpnt = tmpname;
}
/*
* Skip hidden or associated files unless hide or showassoc,
* respectively, is set
*/
match = 0;
if (dlen > 0 &&
(sbi->s_hide =='n' ||
(!(de->flags[-sbi->s_high_sierra] & 1))) &&
(sbi->s_showassoc =='y' ||
(!(de->flags[-sbi->s_high_sierra] & 4)))) {
match = (isofs_cmp(dentry, dpnt, dlen) == 0);
}
if (match) {
isofs_normalize_block_and_offset(de,
&block_saved,
&offset_saved);
*block_rv = block_saved;
*offset_rv = offset_saved;
brelse(bh);
return 1;
}
}
brelse(bh);
return 0;
}
struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
int found;
unsigned long uninitialized_var(block);
unsigned long uninitialized_var(offset);
struct inode *inode;
struct page *page;
dentry->d_op = dir->i_sb->s_root->d_op;
page = alloc_page(GFP_USER);
if (!page)
return ERR_PTR(-ENOMEM);
lock_kernel();
found = isofs_find_entry(dir, dentry,
&block, &offset,
page_address(page),
1024 + page_address(page));
__free_page(page);
inode = NULL;
if (found) {
inode = isofs_iget(dir->i_sb, block, offset);
if (IS_ERR(inode)) {
unlock_kernel();
return ERR_CAST(inode);
}
}
unlock_kernel();
return d_splice_alias(inode, dentry);
}