Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Sat, 13 Aug 2016 18:42:58 +0100 | Subject | [PATCH 3.2 86/94] proc: prevent stacking filesystems on top |
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3.2.82-rc1 review patch. If anyone has any objections, please let me know.
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From: Jann Horn <jannh@google.com>
commit e54ad7f1ee263ffa5a2de9c609d58dfa27b21cd9 upstream.
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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- fs/proc/root.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -53,6 +53,13 @@ static struct dentry *proc_mount(struct 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 (!sb->s_root) { sb->s_flags = flags; err = proc_fill_super(sb);
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