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42 lines
1.3 KiB
Diff
42 lines
1.3 KiB
Diff
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From e54ad7f1ee263ffa5a2de9c609d58dfa27b21cd9 Mon Sep 17 00:00:00 2001
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From: Jann Horn <jannh@google.com>
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Date: Wed, 1 Jun 2016 11:55:05 +0200
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Subject: proc: prevent stacking filesystems on top
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This prevents stacking filesystems (ecryptfs and overlayfs) from using
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procfs as lower filesystem. There is too much magic going on inside
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procfs, and there is no good reason to stack stuff on top of procfs.
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(For example, procfs does access checks in VFS open handlers, and
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ecryptfs by design calls open handlers from a kernel thread that doesn't
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drop privileges or so.)
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Signed-off-by: Jann Horn <jannh@google.com>
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Cc: stable@vger.kernel.org
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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fs/proc/root.c | 7 +++++++
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1 file changed, 7 insertions(+)
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diff --git a/fs/proc/root.c b/fs/proc/root.c
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index 361ab4e..ec649c9 100644
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--- a/fs/proc/root.c
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+++ b/fs/proc/root.c
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@@ -121,6 +121,13 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
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if (IS_ERR(sb))
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return ERR_CAST(sb);
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+ /*
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+ * procfs isn't actually a stacking filesystem; however, there is
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+ * too much magic going on inside it to permit stacking things on
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+ * top of it
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+ */
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+ sb->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
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+
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if (!proc_parse_options(options, ns)) {
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deactivate_locked_super(sb);
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return ERR_PTR(-EINVAL);
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--
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cgit v1.1
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