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authorJann Horn <jannh@google.com>2016-06-01 11:55:05 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2016-06-10 12:09:43 -0700
commite54ad7f1ee263ffa5a2de9c609d58dfa27b21cd9 (patch)
tree06fb2c592c36590d5819972a8645daec03de8c65
parent2dcd0af568b0cf583645c8a317dd12e344b1c72a (diff)
downloadlinux-e54ad7f1ee263ffa5a2de9c609d58dfa27b21cd9.tar.gz
proc: prevent stacking filesystems on top
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>
-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 361ab4ee42fc..ec649c92d270 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);