lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-Id: <1371843030-24038-2-git-send-email-tytso@mit.edu> Date: Fri, 21 Jun 2013 15:30:30 -0400 From: Theodore Ts'o <tytso@....edu> To: Ext4 Developers List <linux-ext4@...r.kernel.org> Cc: desrt@...rt.ca, Theodore Ts'o <tytso@....edu> Subject: [PATCH 2/2] ext4: allocate delayed allocation blocks before rename When ext4_rename() overwrites an already existing file, call ext4_alloc_da_blocks() before starting the journal handle which actually does the rename, instead of doing this afterwards. This improves the likelihood that the contents will survive a crash if an application replaces a file using the sequence: 1) write replacement contents to foo.new 2) <omit fsync of foo.new> 3) rename foo.new to foo It is still not a guarantee, since ext4_alloc_da_blocks() is *not* doing a file integrity sync; this means if foo.new is a very large file, it may not be completely flushed out to disk. However, for files smaller than a megabyte or so, any dirty pages should be flushed out before we do the rename operation, and so at the next journal commit, the CACHE FLUSH command will make sure al of these pages are safely on the disk platter. Signed-off-by: "Theodore Ts'o" <tytso@....edu> --- fs/ext4/namei.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index f57980c..ca8174b 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -2961,6 +2961,10 @@ static struct buffer_head *ext4_get_first_dir_block(handle_t *handle, /* * Anybody can rename anything with this: the permission checks are left to the * higher-level routines. + * + * n.b. old_{dentry,inode) refers to the source dentry/inode + * while new_{dentry,inode) refers to the destination dentry/inode + * This comes from rename(const char *oldpath, const char *newpath) */ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) @@ -2969,7 +2973,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *old_inode, *new_inode; struct buffer_head *old_bh, *new_bh, *dir_bh; struct ext4_dir_entry_2 *old_de, *new_de; - int retval, force_da_alloc = 0; + int retval; int inlined = 0, new_inlined = 0; struct ext4_dir_entry_2 *parent_de; @@ -3004,6 +3008,8 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, new_bh = NULL; } } + if (new_inode && !test_opt(new_dir->i_sb, NO_AUTO_DA_ALLOC)) + ext4_alloc_da_blocks(old_inode); handle = ext4_journal_start(old_dir, EXT4_HT_DIR, (2 * EXT4_DATA_TRANS_BLOCKS(old_dir->i_sb) + @@ -3144,8 +3150,6 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, ext4_mark_inode_dirty(handle, new_inode); if (!new_inode->i_nlink) ext4_orphan_add(handle, new_inode); - if (!test_opt(new_dir->i_sb, NO_AUTO_DA_ALLOC)) - force_da_alloc = 1; } retval = 0; @@ -3155,8 +3159,6 @@ end_rename: brelse(new_bh); if (handle) ext4_journal_stop(handle); - if (retval == 0 && force_da_alloc) - ext4_alloc_da_blocks(old_inode); return retval; } -- 1.7.12.rc0.22.gcdd159b -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists