From 0834136aeaf0e79fc428bfae78340e16719a2a20 Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Wed, 21 Feb 2018 11:36:52 -0500 Subject: [PATCH] fuse: define the filesystem as untrusted Files on FUSE can change at any point in time without IMA being able to detect it. The file data read for the file signature verification could be totally different from what is subsequently read, making the signature verification useless. FUSE can be mounted by unprivileged users either today with fusermount installed with setuid, or soon with the upcoming patches to allow FUSE mounts in a non-init user namespace. This patch sets the SB_I_IMA_UNVERIFIABLE_SIGNATURE flag and when appropriate sets the SB_I_UNTRUSTED_MOUNTER flag. Signed-off-by: Mimi Zohar Cc: Miklos Szeredi Cc: Seth Forshee Cc: Dongsu Park Cc: Alban Crequy Acked-by: Serge Hallyn Acked-by: "Eric W. Biederman" --- fs/fuse/inode.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 624f18bbfd2b..ef309958e060 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1080,6 +1080,9 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) sb->s_maxbytes = MAX_LFS_FILESIZE; sb->s_time_gran = 1; sb->s_export_op = &fuse_export_operations; + sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE; + if (sb->s_user_ns != &init_user_ns) + sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER; file = fget(d.fd); err = -EINVAL;