linux.git/kernel/bpf/syscall.c, branch v5.7-rc2

bpf: Prevent re-mmap()'ing BPF map as writable for initially r/o mapping

2020-04-14T19:28:57+00:00

VM_MAYWRITE flag during initial memory mapping determines if already mmap()'ed
pages can be later remapped as writable ones through mprotect() call. To
prevent user application to rewrite contents of memory-mapped as read-only and
subsequently frozen BPF map, remove VM_MAYWRITE flag completely on initially
read-only mapping.

Alternatively, we could treat any memory-mapping on unfrozen map as writable
and bump writecnt instead. But there is little legitimate reason to map
BPF map as read-only and then re-mmap() it as writable through mprotect(),
instead of just mmap()'ing it as read/write from the very beginning.

Also, at the suggestion of Jann Horn, drop unnecessary refcounting in mmap
operations. We can just rely on VMA holding reference to BPF map's file
properly.

Fixes: fc9702273e2e ("bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY")
Reported-by: Jann Horn 
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Daniel Borkmann 
Reviewed-by: Jann Horn 
Link: https://lore.kernel.org/bpf/20200410202613.3679837-1-andriin@fb.com

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2020-03-31T02:52:37+00:00

Signed-off-by: David S. Miller

bpf: Implement bpf_prog replacement for an active bpf_cgroup_link

2020-03-31T00:36:33+00:00

Add new operation (LINK_UPDATE), which allows to replace active bpf_prog from
under given bpf_link. Currently this is only supported for bpf_cgroup_link,
but will be extended to other kinds of bpf_links in follow-up patches.

For bpf_cgroup_link, implemented functionality matches existing semantics for
direct bpf_prog attachment (including BPF_F_REPLACE flag). User can either
unconditionally set new bpf_prog regardless of which bpf_prog is currently
active under given bpf_link, or, optionally, can specify expected active
bpf_prog. If active bpf_prog doesn't match expected one, no changes are
performed, old bpf_link stays intact and attached, operation returns
a failure.

cgroup_bpf_replace() operation is resolving race between auto-detachment and
bpf_prog update in the same fashion as it's done for bpf_link detachment,
except in this case update has no way of succeeding because of target cgroup
marked as dying. So in this case error is returned.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20200330030001.2312810-3-andriin@fb.com

bpf: Implement bpf_link-based cgroup BPF program attachment

2020-03-31T00:35:59+00:00

Implement new sub-command to attach cgroup BPF programs and return FD-based
bpf_link back on success. bpf_link, once attached to cgroup, cannot be
replaced, except by owner having its FD. Cgroup bpf_link supports only
BPF_F_ALLOW_MULTI semantics. Both link-based and prog-based BPF_F_ALLOW_MULTI
attachments can be freely intermixed.

To prevent bpf_cgroup_link from keeping cgroup alive past the point when no
BPF program can be executed, implement auto-detachment of link. When
cgroup_bpf_release() is called, all attached bpf_links are forced to release
cgroup refcounts, but they leave bpf_link otherwise active and allocated, as
well as still owning underlying bpf_prog. This is because user-space might
still have FDs open and active, so bpf_link as a user-referenced object can't
be freed yet. Once last active FD is closed, bpf_link will be freed and
underlying bpf_prog refcount will be dropped. But cgroup refcount won't be
touched, because cgroup is released already.

The inherent race between bpf_cgroup_link release (from closing last FD) and
cgroup_bpf_release() is resolved by both operations taking cgroup_mutex. So
the only additional check required is when bpf_cgroup_link attempts to detach
itself from cgroup. At that time we need to check whether there is still
cgroup associated with that link. And if not, exit with success, because
bpf_cgroup_link was already successfully detached.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Acked-by: Roman Gushchin 
Link: https://lore.kernel.org/bpf/20200330030001.2312810-2-andriin@fb.com

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2020-03-30T04:25:29+00:00

Minor comment conflict in mac80211.

Signed-off-by: David S. Miller

bpf: lsm: Implement attach, detach and execution

2020-03-29T23:34:00+00:00

JITed BPF programs are dynamically attached to the LSM hooks
using BPF trampolines. The trampoline prologue generates code to handle
conversion of the signature of the hook to the appropriate BPF context.

The allocated trampoline programs are attached to the nop functions
initialized as LSM hooks.

BPF_PROG_TYPE_LSM programs must have a GPL compatible license and
and need CAP_SYS_ADMIN (required for loading eBPF programs).

Upon attachment:

* A BPF fexit trampoline is used for LSM hooks with a void return type.
* A BPF fmod_ret trampoline is used for LSM hooks which return an
  int. The attached programs can override the return value of the
  bpf LSM hook to indicate a MAC Policy decision.

Signed-off-by: KP Singh 
Signed-off-by: Daniel Borkmann 
Reviewed-by: Brendan Jackman 
Reviewed-by: Florent Revest 
Acked-by: Andrii Nakryiko 
Acked-by: James Morris 
Link: https://lore.kernel.org/bpf/20200329004356.27286-5-kpsingh@chromium.org

bpf: Remove unused vairable 'bpf_xdp_link_lops'

2020-03-26T23:46:32+00:00

kernel/bpf/syscall.c:2263:34: warning: 'bpf_xdp_link_lops' defined but not used [-Wunused-const-variable=]
 static const struct bpf_link_ops bpf_xdp_link_lops;
                                  ^~~~~~~~~~~~~~~~~

commit 70ed506c3bbc ("bpf: Introduce pinnable bpf_link abstraction")
involded this unused variable, remove it.

Reported-by: Hulk Robot 
Signed-off-by: YueHaibing 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20200326031613.19372-1-yuehaibing@huawei.com

bpf: Factor out attach_type to prog_type mapping for attach/detach

2020-03-26T23:38:13+00:00

Factor out logic mapping expected program attach type to program type and
subsequent handling of program attach/detach. Also list out all supported
cgroup BPF program types explicitly to prevent accidental bugs once more
program types are added to a mapping. Do the same for prog_query API.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20200325065746.640559-3-andriin@fb.com

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2020-03-26T01:58:11+00:00

Overlapping header include additions in macsec.c

A bug fix in 'net' overlapping with the removal of 'version'
string in ena_netdev.c

Overlapping test additions in selftests Makefile

Overlapping PCI ID table adjustments in iwlwifi driver.

Signed-off-by: David S. Miller

bpf: Explicitly memset some bpf info structures declared on the stack

2020-03-20T20:05:22+00:00

Trying to initialize a structure with "= {};" will not always clean out
all padding locations in a structure. So be explicit and call memset to
initialize everything for a number of bpf information structures that
are then copied from userspace, sometimes from smaller memory locations
than the size of the structure.

Reported-by: Daniel Borkmann 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Daniel Borkmann 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20200320162258.GA794295@kroah.com