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ext4 crypto: allocate the right amount of memory for the on-disk symlink

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Previously we were taking the required padding when allocating space
for the on-disk symlink.  This caused a buffer overrun which could
trigger a krenel crash when running fsstress.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2015-05-31 13:35:32 -04:00
parent 82d0d3e7e6
commit 4d3c4e5b8c
3 changed files with 37 additions and 21 deletions
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25
fs/ext4/crypto_fname.c
View File

@ -262,8 +262,20 @@ u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
return ((size+blksize-1)/blksize)*blksize;
}
/**
* ext4_fname_crypto_alloc_obuff() -
unsigned ext4_fname_encrypted_size(struct inode *inode, u32 ilen)
{
struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
int padding = 32;
if (ci)
padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK);
if (ilen < EXT4_CRYPTO_BLOCK_SIZE)
ilen = EXT4_CRYPTO_BLOCK_SIZE;
return ext4_fname_crypto_round_up(ilen, padding);
}
/*
* ext4_fname_crypto_alloc_buffer() -
*
* Allocates an output buffer that is sufficient for the crypto operation
* specified by the context and the direction.
@ -271,15 +283,8 @@ u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
int ext4_fname_crypto_alloc_buffer(struct inode *inode,
u32 ilen, struct ext4_str *crypto_str)
{
unsigned int olen;
int padding = 16;
struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
unsigned int olen = ext4_fname_encrypted_size(inode, ilen);
if (ci)
padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK);
if (padding < EXT4_CRYPTO_BLOCK_SIZE)
padding = EXT4_CRYPTO_BLOCK_SIZE;
olen = ext4_fname_crypto_round_up(ilen, padding);
crypto_str->len = olen;
if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;

1
fs/ext4/ext4.h
View File

@ -2090,6 +2090,7 @@ static inline int ext4_sb_has_crypto(struct super_block *sb)
/* crypto_fname.c */
bool ext4_valid_filenames_enc_mode(uint32_t mode);
u32 ext4_fname_crypto_round_up(u32 size, u32 blksize);
unsigned ext4_fname_encrypted_size(struct inode *inode, u32 ilen);
int ext4_fname_crypto_alloc_buffer(struct inode *inode,
u32 ilen, struct ext4_str *crypto_str);
int _ext4_fname_disk_to_usr(struct inode *inode,

32
fs/ext4/namei.c
View File

@ -3039,10 +3039,23 @@ static int ext4_symlink(struct inode *dir,
encryption_required = (ext4_encrypted_inode(dir) ||
DUMMY_ENCRYPTION_ENABLED(EXT4_SB(dir->i_sb)));
if (encryption_required)
disk_link.len = encrypted_symlink_data_len(len) + 1;
if (disk_link.len > dir->i_sb->s_blocksize)
return -ENAMETOOLONG;
if (encryption_required) {
err = ext4_get_encryption_info(dir);
if (err)
return err;
if (ext4_encryption_info(dir) == NULL)
return -EPERM;
disk_link.len = (ext4_fname_encrypted_size(dir, len) +
sizeof(struct ext4_encrypted_symlink_data));
sd = kzalloc(disk_link.len, GFP_KERNEL);
if (!sd)
return -ENOMEM;
}
if (disk_link.len > dir->i_sb->s_blocksize) {
err = -ENAMETOOLONG;
goto err_free_sd;
}
dquot_initialize(dir);
@ -3073,18 +3086,14 @@ static int ext4_symlink(struct inode *dir,
if (IS_ERR(inode)) {
if (handle)
ext4_journal_stop(handle);
return PTR_ERR(inode);
err = PTR_ERR(inode);
goto err_free_sd;
}
if (encryption_required) {
struct qstr istr;
struct ext4_str ostr;
sd = kzalloc(disk_link.len, GFP_NOFS);
if (!sd) {
err = -ENOMEM;
goto err_drop_inode;
}
istr.name = (const unsigned char *) symname;
istr.len = len;
ostr.name = sd->encrypted_path;
@ -3156,10 +3165,11 @@ static int ext4_symlink(struct inode *dir,
err_drop_inode:
if (handle)
ext4_journal_stop(handle);
kfree(sd);
clear_nlink(inode);
unlock_new_inode(inode);
iput(inode);
err_free_sd:
kfree(sd);
return err;
}