From 50337475211b91729091507ee0b56252d8b68285 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Mon, 14 May 2012 13:06:14 +0200 Subject: UBUNTU: ubuntu: overlayfs -- fs: limit filesystem stacking depth Add a simple read-only counter to super_block that indicates deep this is in the stack of filesystems. Previously ecryptfs was the only stackable filesystem and it explicitly disallowed multiple layers of itself. Overlayfs, however, can be stacked recursively and also may be stacked on top of ecryptfs or vice versa. To limit the kernel stack usage we must limit the depth of the filesystem stack. Initially the limit is set to 2. Signed-off-by: Miklos Szeredi --- include/linux/fs.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include') diff --git a/include/linux/fs.h b/include/linux/fs.h index 05d046f75e9..49b86cf0564 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -499,6 +499,12 @@ struct iattr { */ #include +/* + * Maximum number of layers of fs stack. Needs to be limited to + * prevent kernel stack overflow + */ +#define FILESYSTEM_MAX_STACK_DEPTH 2 + /** * enum positive_aop_returns - aop return codes with specific semantics * @@ -1542,6 +1548,11 @@ struct super_block { /* Being remounted read-only */ int s_readonly_remount; + + /* + * Indicates how deep in a filesystem stack this SB is + */ + int s_stack_depth; }; /* superblock cache pruning functions */ -- cgit v1.2.3