From: Theodore Ts'o Subject: [PATCH 8/8] ext4 crypto: allocate the right amount of memory for the on-disk symlink Date: Thu, 28 May 2015 19:47:47 -0400 Message-ID: <1432856867-5710-8-git-send-email-tytso@mit.edu> References: <1432856867-5710-1-git-send-email-tytso@mit.edu> Cc: jaegeuk@kernel.org, mhalcrow@google.com, Theodore Ts'o To: Ext4 Developers List Return-path: Received: from imap.thunk.org ([74.207.234.97]:35458 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754921AbbE1Xr5 (ORCPT ); Thu, 28 May 2015 19:47:57 -0400 In-Reply-To: <1432856867-5710-1-git-send-email-tytso@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 --- fs/ext4/crypto_fname.c | 25 +++++++++++++++---------- fs/ext4/ext4.h | 1 + fs/ext4/namei.c | 32 +++++++++++++++++++++----------- 3 files changed, 37 insertions(+), 21 deletions(-) diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c index 23af41f..7dc4eb5 100644 --- a/fs/ext4/crypto_fname.c +++ b/fs/ext4/crypto_fname.c @@ -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; diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index bd8d32d..730c88d 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -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, diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 401b099..bda4a5d 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -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; } -- 2.3.0