On 11/29/21 10:33 PM, David Howells wrote:
> +/*
> + * turn the raw key into something cooked
> + * - the key may be up to NAME_MAX in length (including the length word)
> + * - "base64" encode the strange keys, mapping 3 bytes of raw to four of
> + * cooked
> + * - need to cut the cooked key into 252 char lengths (189 raw bytes)
> + */
> +bool cachefiles_cook_key(struct cachefiles_object *object)
> +{
> + const u8 *key = fscache_get_key(object->cookie), *kend;
> + unsigned char ch;
> + unsigned int acc, i, n, nle, nbe, keylen = object->cookie->key_len;
> + unsigned int b64len, len, print, pad;
> + char *name, sep;
> +
> + _enter(",%u,%*phN", keylen, keylen, key);
> +
> + BUG_ON(keylen > NAME_MAX - 3);
> +
> + print = 1;
> + for (i = 0; i < keylen; i++) {
> + ch = key[i];
> + print &= cachefiles_filecharmap[ch];
> + }
> +
> + /* If the path is usable ASCII, then we render it directly */
> + if (print) {
> + len = 1 + keylen + 1;
> + name = kmalloc(len, GFP_KERNEL);
> + if (!name)
> + return false;
> +
> + name[0] = 'D'; /* Data object type, string encoding */
> + name[1 + keylen] = 0;
> + memcpy(name + 1, key, keylen);
> + goto success;
^
If we goto success from here,
> + }
> +
> + /* See if it makes sense to encode it as "hex,hex,hex" for each 32-bit
> + * chunk. We rely on the key having been padded out to a whole number
> + * of 32-bit words.
> + */
> + n = round_up(keylen, 4);
> + nbe = nle = 0;
> + for (i = 0; i < n; i += 4) {
> + u32 be = be32_to_cpu(*(__be32 *)(key + i));
> + u32 le = le32_to_cpu(*(__le32 *)(key + i));
> +
> + nbe += 1 + how_many_hex_digits(be);
> + nle += 1 + how_many_hex_digits(le);
> + }
> +
> + b64len = DIV_ROUND_UP(keylen, 3);
> + pad = b64len * 3 - keylen;
> + b64len = 2 + b64len * 4; /* Length if we base64-encode it */
> + _debug("len=%u nbe=%u nle=%u b64=%u", keylen, nbe, nle, b64len);
> + if (nbe < b64len || nle < b64len) {
> + unsigned int nlen = min(nbe, nle) + 1;
> + name = kmalloc(nlen, GFP_KERNEL);
> + if (!name)
> + return false;
> + sep = (nbe <= nle) ? 'S' : 'T'; /* Encoding indicator */
> + len = 0;
> + for (i = 0; i < n; i += 4) {
> + u32 x;
> + if (nbe <= nle)
> + x = be32_to_cpu(*(__be32 *)(key + i));
> + else
> + x = le32_to_cpu(*(__le32 *)(key + i));
> + name[len++] = sep;
> + if (x != 0)
> + len += snprintf(name + len, nlen - len, "%x",
> x);
> + sep = ',';
> + }
> + goto success;
> + }
> +
> + /* We need to base64-encode it */
> + name = kmalloc(b64len + 1, GFP_KERNEL);
> + if (!name)
> + return false;
> +
> + name[0] = 'E';
> + name[1] = '0' + pad;
> + len = 2;
> + kend = key + keylen;
> + do {
> + acc = *key++;
> + if (key < kend) {
> + acc |= *key++ << 8;
> + if (key < kend)
> + acc |= *key++ << 16;
> + }
> +
> + name[len++] = cachefiles_charmap[acc & 63];
> + acc >>= 6;
> + name[len++] = cachefiles_charmap[acc & 63];
> + acc >>= 6;
> + name[len++] = cachefiles_charmap[acc & 63];
> + acc >>= 6;
> + name[len++] = cachefiles_charmap[acc & 63];
> + } while (key < kend);
> +
> +success:
> + name[len] = 0;
^
then it seems that this will cause an out-of-boundary access.
> + object->d_name = name;
> + object->d_name_len = len;
> + _leave(" = %s", object->d_name);
> + return true;
> +}
>
--
Thanks,
Jeffle
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