linux/fs/f2fs/hash.c
Jaegeuk Kim 6332cd32c8 f2fs: check entire encrypted bigname when finding a dentry
If user has no key under an encrypted dir, fscrypt gives digested dentries.
Previously, when looking up a dentry, f2fs only checks its hash value with
first 4 bytes of the digested dentry, which didn't handle hash collisions fully.
This patch enhances to check entire dentry bytes likewise ext4.

Eric reported how to reproduce this issue by:

 # seq -f "edir/abcdefghijklmnopqrstuvwxyz012345%.0f" 100000 | xargs touch
 # find edir -type f | xargs stat -c %i | sort | uniq | wc -l
100000
 # sync
 # echo 3 > /proc/sys/vm/drop_caches
 # keyctl new_session
 # find edir -type f | xargs stat -c %i | sort | uniq | wc -l
99999

Cc: <stable@vger.kernel.org>
Reported-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(fixed f2fs_dentry_hash() to work even when the hash is 0)
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2017-05-04 11:44:35 -04:00

109 lines
2.2 KiB
C

/*
* fs/f2fs/hash.c
*
* Copyright (c) 2012 Samsung Electronics Co., Ltd.
* http://www.samsung.com/
*
* Portions of this code from linux/fs/ext3/hash.c
*
* Copyright (C) 2002 by Theodore Ts'o
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/f2fs_fs.h>
#include <linux/cryptohash.h>
#include <linux/pagemap.h>
#include "f2fs.h"
/*
* Hashing code copied from ext3
*/
#define DELTA 0x9E3779B9
static void TEA_transform(unsigned int buf[4], unsigned int const in[])
{
__u32 sum = 0;
__u32 b0 = buf[0], b1 = buf[1];
__u32 a = in[0], b = in[1], c = in[2], d = in[3];
int n = 16;
do {
sum += DELTA;
b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
} while (--n);
buf[0] += b0;
buf[1] += b1;
}
static void str2hashbuf(const unsigned char *msg, size_t len,
unsigned int *buf, int num)
{
unsigned pad, val;
int i;
pad = (__u32)len | ((__u32)len << 8);
pad |= pad << 16;
val = pad;
if (len > num * 4)
len = num * 4;
for (i = 0; i < len; i++) {
if ((i % 4) == 0)
val = pad;
val = msg[i] + (val << 8);
if ((i % 4) == 3) {
*buf++ = val;
val = pad;
num--;
}
}
if (--num >= 0)
*buf++ = val;
while (--num >= 0)
*buf++ = pad;
}
f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
struct fscrypt_name *fname)
{
__u32 hash;
f2fs_hash_t f2fs_hash;
const unsigned char *p;
__u32 in[8], buf[4];
const unsigned char *name = name_info->name;
size_t len = name_info->len;
/* encrypted bigname case */
if (fname && !fname->disk_name.name)
return cpu_to_le32(fname->hash);
if (is_dot_dotdot(name_info))
return 0;
/* Initialize the default seed for the hash checksum functions */
buf[0] = 0x67452301;
buf[1] = 0xefcdab89;
buf[2] = 0x98badcfe;
buf[3] = 0x10325476;
p = name;
while (1) {
str2hashbuf(p, len, in, 4);
TEA_transform(buf, in);
p += 16;
if (len <= 16)
break;
len -= 16;
}
hash = buf[0];
f2fs_hash = cpu_to_le32(hash & ~F2FS_HASH_COL_BIT);
return f2fs_hash;
}