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authorJann Horn <jannh@google.com>2016-06-01 11:55:05 +0200
committerSasha Levin <sasha.levin@oracle.com>2016-06-19 23:47:46 -0400
commit70e21269e3ec8e4345e7fcd263f9a8f2a43f42df (patch)
tree7d51757c724b3398e3d3d1faf5c57023964b4169
parent8cb589e0d094c522e1103563c17881c31d5e9a69 (diff)
downloadlinux-linaro-stable-70e21269e3ec8e4345e7fcd263f9a8f2a43f42df.tar.gz
proc: prevent stacking filesystems on top
[ Upstream commit e54ad7f1ee263ffa5a2de9c609d58dfa27b21cd9 ] This prevents stacking filesystems (ecryptfs and overlayfs) from using procfs as lower filesystem. There is too much magic going on inside procfs, and there is no good reason to stack stuff on top of procfs. (For example, procfs does access checks in VFS open handlers, and ecryptfs by design calls open handlers from a kernel thread that doesn't drop privileges or so.) Signed-off-by: Jann Horn <jannh@google.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
-rw-r--r--fs/proc/root.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 9e772f1a5386..7863ed5a6a88 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -121,6 +121,13 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
if (IS_ERR(sb))
return ERR_CAST(sb);
+ /*
+ * procfs isn't actually a stacking filesystem; however, there is
+ * too much magic going on inside it to permit stacking things on
+ * top of it
+ */
+ sb->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
+
if (!proc_parse_options(options, ns)) {
deactivate_locked_super(sb);
return ERR_PTR(-EINVAL);