diff options
| -rw-r--r-- | fs/overlayfs/file.c | 4 | ||||
| -rw-r--r-- | fs/overlayfs/inode.c | 21 |
2 files changed, 23 insertions, 2 deletions
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index e235a635d9ec..859efeaaefab 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -171,7 +171,7 @@ static loff_t ovl_llseek(struct file *file, loff_t offset, int whence) * limitations that are more strict than ->s_maxbytes for specific * files, so we use the real file to perform seeks. */ - inode_lock(inode); + ovl_inode_lock(inode); real.file->f_pos = file->f_pos; old_cred = ovl_override_creds(inode->i_sb); @@ -179,7 +179,7 @@ static loff_t ovl_llseek(struct file *file, loff_t offset, int whence) revert_creds(old_cred); file->f_pos = real.file->f_pos; - inode_unlock(inode); + ovl_inode_unlock(inode); fdput(real); diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index bfebef7638ca..13981b0a8235 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -527,6 +527,27 @@ static const struct address_space_operations ovl_aops = { * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2) * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1) * [...] &type->i_mutex_dir_key (stack_depth=0) + * + * Locking order w.r.t ovl_want_write() is important for nested overlayfs. + * + * This chain is valid: + * - inode->i_rwsem (inode_lock[2]) + * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0]) + * - OVL_I(inode)->lock (ovl_inode_lock[2]) + * - OVL_I(lowerinode)->lock (ovl_inode_lock[1]) + * + * And this chain is valid: + * - inode->i_rwsem (inode_lock[2]) + * - OVL_I(inode)->lock (ovl_inode_lock[2]) + * - lowerinode->i_rwsem (inode_lock[1]) + * - OVL_I(lowerinode)->lock (ovl_inode_lock[1]) + * + * But lowerinode->i_rwsem SHOULD NOT be acquired while ovl_want_write() is + * held, because it is in reverse order of the non-nested case using the same + * upper fs: + * - inode->i_rwsem (inode_lock[1]) + * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0]) + * - OVL_I(inode)->lock (ovl_inode_lock[1]) */ #define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH |