73 lines
2.3 KiB
Diff
73 lines
2.3 KiB
Diff
From 48a6c91c1d967cc8375621509676a9eabfac5777 Mon Sep 17 00:00:00 2001
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From: Miklos Szeredi <mszeredi@suse.cz>
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Date: Fri, 24 Oct 2014 00:14:39 +0200
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Subject: [PATCH] BACKPORT: fs: limit filesystem stacking depth
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Add a simple read-only counter to super_block that indicates how deep this
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is in the stack of filesystems. Previously ecryptfs was the only stackable
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filesystem and it explicitly disallowed multiple layers of itself.
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Overlayfs, however, can be stacked recursively and also may be stacked
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on top of ecryptfs or vice versa.
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To limit the kernel stack usage we must limit the depth of the
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filesystem stack. Initially the limit is set to 2.
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Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
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(cherry picked from commit 69c433ed2ecd2d3264efd7afec4439524b319121)
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Bug: 32761463
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Change-Id: I69b2fba2112db2ece09a1bf61a44f8fc4db00820
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---
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fs/ecryptfs/main.c | 7 +++++++
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include/linux/fs.h | 10 ++++++++++
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2 files changed, 17 insertions(+)
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diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
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index 329a9cc2b2ebe..8a041bb0753fa 100644
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--- a/fs/ecryptfs/main.c
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+++ b/fs/ecryptfs/main.c
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@@ -577,6 +577,13 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
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s->s_maxbytes = path.dentry->d_sb->s_maxbytes;
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s->s_blocksize = path.dentry->d_sb->s_blocksize;
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s->s_magic = ECRYPTFS_SUPER_MAGIC;
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+ s->s_stack_depth = path.dentry->d_sb->s_stack_depth + 1;
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+
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+ rc = -EINVAL;
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+ if (s->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
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+ pr_err("eCryptfs: maximum fs stacking depth exceeded\n");
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+ goto out_free;
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+ }
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inode = ecryptfs_get_inode(path.dentry->d_inode, s);
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rc = PTR_ERR(inode);
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diff --git a/include/linux/fs.h b/include/linux/fs.h
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index 1bbd26958874f..0d1e1680f3657 100644
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--- a/include/linux/fs.h
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+++ b/include/linux/fs.h
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@@ -244,6 +244,12 @@ struct iattr {
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*/
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#include <linux/quota.h>
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+/*
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+ * Maximum number of layers of fs stack. Needs to be limited to
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+ * prevent kernel stack overflow
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+ */
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+#define FILESYSTEM_MAX_STACK_DEPTH 2
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+
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/**
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* enum positive_aop_returns - aop return codes with specific semantics
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*
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@@ -1331,6 +1337,10 @@ struct super_block {
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/* AIO completions deferred from interrupt context */
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struct workqueue_struct *s_dio_done_wq;
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+ /*
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+ * Indicates how deep in a filesystem stack this SB is
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+ */
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+ int s_stack_depth;
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};
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/* superblock cache pruning functions */
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