On Wed, Sep 14, 2016 at 12:24 AM, Mickaël Salaün <mic@xxxxxxxxxxx> wrote: > Add eBPF functions to compare file system access with a Landlock file > system handle: > * bpf_landlock_cmp_fs_prop_with_struct_file(prop, map, map_op, file) > This function allows to compare the dentry, inode, device or mount > point of the currently accessed file, with a reference handle. > * bpf_landlock_cmp_fs_beneath_with_struct_file(opt, map, map_op, file) > This function allows an eBPF program to check if the current accessed > file is the same or in the hierarchy of a reference handle. > > The goal of file system handle is to abstract kernel objects such as a > struct file or a struct inode. Userland can create this kind of handle > thanks to the BPF_MAP_UPDATE_ELEM command. The element is a struct > landlock_handle containing the handle type (e.g. > BPF_MAP_HANDLE_TYPE_LANDLOCK_FS_FD) and a file descriptor. This could > also be any descriptions able to match a struct file or a struct inode > (e.g. path or glob string). > > Changes since v2: > * add MNT_INTERNAL check to only add file handle from user-visible FS > (e.g. no anonymous inode) > * replace struct file* with struct path* in map_landlock_handle > * add BPF protos > * fix bpf_landlock_cmp_fs_prop_with_struct_file() > > Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> > Cc: Alexei Starovoitov <ast@xxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> > Cc: David S. Miller <davem@xxxxxxxxxxxxx> > Cc: James Morris <james.l.morris@xxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Serge E. Hallyn <serge@xxxxxxxxxx> > Link: https://lkml.kernel.org/r/CALCETrWwTiz3kZTkEgOW24-DvhQq6LftwEXh77FD2G5o71yD7g@xxxxxxxxxxxxxx > --- > include/linux/bpf.h | 10 +++ > include/uapi/linux/bpf.h | 49 +++++++++++ > kernel/bpf/arraymap.c | 21 +++++ > kernel/bpf/verifier.c | 8 ++ > security/landlock/Makefile | 2 +- > security/landlock/checker_fs.c | 179 +++++++++++++++++++++++++++++++++++++++++ > security/landlock/checker_fs.h | 20 +++++ > security/landlock/lsm.c | 6 ++ > 8 files changed, 294 insertions(+), 1 deletion(-) > create mode 100644 security/landlock/checker_fs.c > create mode 100644 security/landlock/checker_fs.h > [...] > diff --git a/security/landlock/checker_fs.c b/security/landlock/checker_fs.c > new file mode 100644 > index 000000000000..39eb85dc7d18 > --- /dev/null > +++ b/security/landlock/checker_fs.c > @@ -0,0 +1,179 @@ > +/* > + * Landlock LSM - File System Checkers > + * > + * Copyright (C) 2016 Mickaël Salaün <mic@xxxxxxxxxxx> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2, as > + * published by the Free Software Foundation. > + */ > + > +#include <linux/bpf.h> /* enum bpf_map_array_op */ > +#include <linux/errno.h> > +#include <linux/fs.h> /* path_is_under() */ > +#include <linux/path.h> /* struct path */ > + > +#include "checker_fs.h" > + > +#define EQUAL_NOT_NULL(a, b) (a && a == b) > + > +/* > + * bpf_landlock_cmp_fs_prop_with_struct_file > + * > + * Cf. include/uapi/linux/bpf.h > + */ > +static inline u64 bpf_landlock_cmp_fs_prop_with_struct_file(u64 r1_property, > + u64 r2_map, u64 r3_map_op, u64 r4_file, u64 r5) > +{ > + u8 property = (u8) r1_property; > + struct bpf_map *map = (struct bpf_map *) (unsigned long) r2_map; > + enum bpf_map_array_op map_op = r3_map_op; > + struct file *file = (struct file *) (unsigned long) r4_file; > + struct bpf_array *array = container_of(map, struct bpf_array, map); > + struct path *p1, *p2; > + struct map_landlock_handle *handle; > + int i; > + > + /* ARG_CONST_PTR_TO_LANDLOCK_HANDLE_FS is an arraymap */ > + if (unlikely(!map)) { > + WARN_ON(1); > + return -EFAULT; > + } Just some minor style/readability nits... This is more readable as: if (WARN_ON(!map)) return -EFAULT; (WARN_ON already includes the unlikely() and passes through the test result.) > + if (unlikely(!file)) > + return -ENOENT; > + if (unlikely((property | _LANDLOCK_FLAG_FS_MASK) != _LANDLOCK_FLAG_FS_MASK)) > + return -EINVAL; > + > + /* for now, only handle OP_OR */ > + switch (map_op) { > + case BPF_MAP_ARRAY_OP_OR: > + break; > + case BPF_MAP_ARRAY_OP_UNSPEC: > + case BPF_MAP_ARRAY_OP_AND: > + case BPF_MAP_ARRAY_OP_XOR: > + default: > + return -EINVAL; > + } > + p2 = &file->f_path; > + > + synchronize_rcu(); > + > + for (i = 0; i < array->n_entries; i++) { > + bool result_dentry = !(property & LANDLOCK_FLAG_FS_DENTRY); > + bool result_inode = !(property & LANDLOCK_FLAG_FS_INODE); > + bool result_device = !(property & LANDLOCK_FLAG_FS_DEVICE); > + bool result_mount = !(property & LANDLOCK_FLAG_FS_MOUNT); > + > + handle = (struct map_landlock_handle *) > + (array->value + array->elem_size * i); > + > + if (handle->type != BPF_MAP_HANDLE_TYPE_LANDLOCK_FS_FD) { > + WARN_ON(1); > + return -EFAULT; > + } Same here... and in the other function (much of which seems to repeat -- can some of these checks be put into common functions?) -Kees -- Kees Cook Nexus Security -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
