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selinux: fix regression introduced by move_mount(2) syscall 

commit 98aa00345de54b8340dc2ddcd87f446d33387b5e upstream.

commit 2db154b3ea ("vfs: syscall: Add move_mount(2) to move mounts around")
introduced a new move_mount(2) system call and a corresponding new LSM
security_move_mount hook but did not implement this hook for any existing
LSM.  This creates a regression for SELinux with respect to consistent
checking of mounts; the existing selinux_mount hook checks mounton
permission to the mount point path.  Provide a SELinux hook
implementation for move_mount that applies this same check for
consistency.  In the future we may wish to add a new move_mount
filesystem permission and check as well, but this addresses
the immediate regression.

Fixes: 2db154b3ea ("vfs: syscall: Add move_mount(2) to move mounts around")
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Stephen Smalley 2020-01-17 15:24:07 -05:00 committed by Greg Kroah-Hartman
parent 3b2e595dfe
commit 875e01dd8a
1 changed files with 10 additions and 0 deletions
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10
security/selinux/hooks.c
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@ -2766,6 +2766,14 @@ static int selinux_mount(const char *dev_name,
return path_has_perm(cred, path, FILE__MOUNTON);
}
static int selinux_move_mount(const struct path *from_path,
const struct path *to_path)
{
const struct cred *cred = current_cred();
return path_has_perm(cred, to_path, FILE__MOUNTON);
}
static int selinux_umount(struct vfsmount *mnt, int flags)
{
const struct cred *cred = current_cred();
@ -6835,6 +6843,8 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(sb_clone_mnt_opts, selinux_sb_clone_mnt_opts),
LSM_HOOK_INIT(sb_add_mnt_opt, selinux_add_mnt_opt),
LSM_HOOK_INIT(move_mount, selinux_move_mount),
LSM_HOOK_INIT(dentry_init_security, selinux_dentry_init_security),
LSM_HOOK_INIT(dentry_create_files_as, selinux_dentry_create_files_as),