Re: [PATCH v3 4/4] fuse: define the filesystem as untrusted
From: Eric W. Biederman <hidden>
Date: 2018-03-13 19:33:46
Also in:
linux-fsdevel, linux-security-module
Possibly related (same subject, not in this thread)
- 2018-03-15 · Re: [PATCH v3 4/4] fuse: define the filesystem as untrusted · Mimi Zohar <hidden>
- 2018-03-15 · Re: [PATCH v3 4/4] fuse: define the filesystem as untrusted · Mimi Zohar <hidden>
- 2018-03-15 · Re: [PATCH v3 4/4] fuse: define the filesystem as untrusted · Chuck Lever <chuck.lever@oracle.com>
- 2018-03-15 · Re: [PATCH v3 4/4] fuse: define the filesystem as untrusted · Stef Bon <hidden>
- 2018-03-14 · Re: [PATCH v3 4/4] fuse: define the filesystem as untrusted · Michael Halcrow <hidden>
Mimi Zohar [off-list ref] writes:
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.
Acked-by: "Eric W. Biederman" <redacted>
quoted hunk
Signed-off-by: Mimi Zohar <redacted> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Seth Forshee <redacted> Cc: Eric W. Biederman <redacted> Cc: Dongsu Park <redacted> Cc: Alban Crequy <redacted> Cc: "Serge E. Hallyn" <serge@hallyn.com> --- 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;