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author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-06-29 19:30:31 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-06-29 19:30:31 +0200 |
commit | 63edbce160c6d68c806e58db026b5881c6010e04 (patch) | |
tree | 1ada31d631d1a8ccec9b4aa9956c54db90c6efcf /fs | |
parent | Merge tag 'for-linus-20130628' of git://git.kernel.org/pub/scm/linux/kernel/g... (diff) | |
parent | UBIFS: fix a horrid bug (diff) | |
download | linux-63edbce160c6d68c806e58db026b5881c6010e04.tar.xz linux-63edbce160c6d68c806e58db026b5881c6010e04.zip |
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull ubifs fixes from Al Viro:
"A couple of ubifs readdir/lseek race fixes. Stable fodder, really
nasty..."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
UBIFS: fix a horrid bug
UBIFS: prepare to fix a horrid bug
Diffstat (limited to 'fs')
-rw-r--r-- | fs/ubifs/dir.c | 54 |
1 files changed, 39 insertions, 15 deletions
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c index de08c92f2e23..605af512aec2 100644 --- a/fs/ubifs/dir.c +++ b/fs/ubifs/dir.c @@ -349,31 +349,50 @@ static unsigned int vfs_dent_type(uint8_t type) static int ubifs_readdir(struct file *file, void *dirent, filldir_t filldir) { int err, over = 0; + loff_t pos = file->f_pos; struct qstr nm; union ubifs_key key; struct ubifs_dent_node *dent; struct inode *dir = file_inode(file); struct ubifs_info *c = dir->i_sb->s_fs_info; - dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, file->f_pos); + dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, pos); - if (file->f_pos > UBIFS_S_KEY_HASH_MASK || file->f_pos == 2) + if (pos > UBIFS_S_KEY_HASH_MASK || pos == 2) /* * The directory was seek'ed to a senseless position or there * are no more entries. */ return 0; + if (file->f_version == 0) { + /* + * The file was seek'ed, which means that @file->private_data + * is now invalid. This may also be just the first + * 'ubifs_readdir()' invocation, in which case + * @file->private_data is NULL, and the below code is + * basically a no-op. + */ + kfree(file->private_data); + file->private_data = NULL; + } + + /* + * 'generic_file_llseek()' unconditionally sets @file->f_version to + * zero, and we use this for detecting whether the file was seek'ed. + */ + file->f_version = 1; + /* File positions 0 and 1 correspond to "." and ".." */ - if (file->f_pos == 0) { + if (pos == 0) { ubifs_assert(!file->private_data); over = filldir(dirent, ".", 1, 0, dir->i_ino, DT_DIR); if (over) return 0; - file->f_pos = 1; + file->f_pos = pos = 1; } - if (file->f_pos == 1) { + if (pos == 1) { ubifs_assert(!file->private_data); over = filldir(dirent, "..", 2, 1, parent_ino(file->f_path.dentry), DT_DIR); @@ -389,7 +408,7 @@ static int ubifs_readdir(struct file *file, void *dirent, filldir_t filldir) goto out; } - file->f_pos = key_hash_flash(c, &dent->key); + file->f_pos = pos = key_hash_flash(c, &dent->key); file->private_data = dent; } @@ -397,17 +416,16 @@ static int ubifs_readdir(struct file *file, void *dirent, filldir_t filldir) if (!dent) { /* * The directory was seek'ed to and is now readdir'ed. - * Find the entry corresponding to @file->f_pos or the - * closest one. + * Find the entry corresponding to @pos or the closest one. */ - dent_key_init_hash(c, &key, dir->i_ino, file->f_pos); + dent_key_init_hash(c, &key, dir->i_ino, pos); nm.name = NULL; dent = ubifs_tnc_next_ent(c, &key, &nm); if (IS_ERR(dent)) { err = PTR_ERR(dent); goto out; } - file->f_pos = key_hash_flash(c, &dent->key); + file->f_pos = pos = key_hash_flash(c, &dent->key); file->private_data = dent; } @@ -419,7 +437,7 @@ static int ubifs_readdir(struct file *file, void *dirent, filldir_t filldir) ubifs_inode(dir)->creat_sqnum); nm.len = le16_to_cpu(dent->nlen); - over = filldir(dirent, dent->name, nm.len, file->f_pos, + over = filldir(dirent, dent->name, nm.len, pos, le64_to_cpu(dent->inum), vfs_dent_type(dent->type)); if (over) @@ -435,9 +453,17 @@ static int ubifs_readdir(struct file *file, void *dirent, filldir_t filldir) } kfree(file->private_data); - file->f_pos = key_hash_flash(c, &dent->key); + file->f_pos = pos = key_hash_flash(c, &dent->key); file->private_data = dent; cond_resched(); + + if (file->f_version == 0) + /* + * The file was seek'ed meanwhile, lets return and start + * reading direntries from the new position on the next + * invocation. + */ + return 0; } out: @@ -448,15 +474,13 @@ out: kfree(file->private_data); file->private_data = NULL; + /* 2 is a special value indicating that there are no more direntries */ file->f_pos = 2; return 0; } -/* If a directory is seeked, we have to free saved readdir() state */ static loff_t ubifs_dir_llseek(struct file *file, loff_t offset, int whence) { - kfree(file->private_data); - file->private_data = NULL; return generic_file_llseek(file, offset, whence); } |