linux-stable.git/kernel/bpf/bpf_struct_ops.c, branch v6.10

bpf: Check return from set_memory_rox()

2024-03-18T21:18:47+00:00

arch_protect_bpf_trampoline() and alloc_new_pack() call
set_memory_rox() which can fail, leading to unprotected memory.

Take into account return from set_memory_rox() function and add
__must_check flag to arch_protect_bpf_trampoline().

Signed-off-by: Christophe Leroy 
Reviewed-by: Kees Cook 
Link: https://lore.kernel.org/r/fe1c163c83767fde5cab31d209a4a6be3ddb3a73.1710574353.git.christophe.leroy@csgroup.eu
Signed-off-by: Martin KaFai Lau

bpf: Remove unnecessary err < 0 check in bpf_struct_ops_map_update_elem

2024-03-18T19:48:10+00:00

There is a "if (err)" check earlier, so the "if (err < 0)"
check that this patch removing is unnecessary. It was my overlook
when making adjustments to the bpf_struct_ops_prepare_trampoline()
such that the caller does not have to worry about the new page when
the function returns error.

Fixes: 187e2af05abe ("bpf: struct_ops supports more than one page for trampolines.")
Signed-off-by: Martin KaFai Lau 
Signed-off-by: Andrii Nakryiko 
Acked-by: Stanislav Fomichev 
Link: https://lore.kernel.org/bpf/20240315192112.2825039-1-martin.lau@linux.dev

bpf: struct_ops supports more than one page for trampolines.

2024-03-04T22:09:20+00:00

The BPF struct_ops previously only allowed one page of trampolines.
Each function pointer of a struct_ops is implemented by a struct_ops
bpf program. Each struct_ops bpf program requires a trampoline.
The following selftest patch shows each page can hold a little more
than 20 trampolines.

While one page is more than enough for the tcp-cc usecase,
the sched_ext use case shows that one page is not always enough and hits
the one page limit. This patch overcomes the one page limit by allocating
another page when needed and it is limited to a total of
MAX_IMAGE_PAGES (8) pages which is more than enough for
reasonable usages.

The variable st_map->image has been changed to st_map->image_pages, and
its type has been changed to an array of pointers to pages.

Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240224223418.526631-3-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau

bpf, net: validate struct_ops when updating value.

2024-03-04T18:03:57+00:00

Perform all validations when updating values of struct_ops maps. Doing
validation in st_ops->reg() and st_ops->update() is not necessary anymore.
However, tcp_register_congestion_control() has been called in various
places. It still needs to do validations.

Cc: netdev@vger.kernel.org
Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240224223418.526631-2-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau

bpf: Check cfi_stubs before registering a struct_ops type.

2024-02-22T20:26:40+00:00

Recently, st_ops->cfi_stubs was introduced. However, the upcoming new
struct_ops support (e.g. sched_ext) is not aware of this and does not
provide its own cfi_stubs. The kernel ends up NULL dereferencing the
st_ops->cfi_stubs.

Considering struct_ops supports kernel module now, this NULL check
is necessary. This patch is to reject struct_ops registration
that does not provide a cfi_stubs.

Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240222021105.1180475-2-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau

bpf: Create argument information for nullable arguments.

2024-02-13T23:16:44+00:00

Collect argument information from the type information of stub functions to
mark arguments of BPF struct_ops programs with PTR_MAYBE_NULL if they are
nullable.  A nullable argument is annotated by suffixing "__nullable" at
the argument name of stub function.

For nullable arguments, this patch sets a struct bpf_ctx_arg_aux to label
their reg_type with PTR_TO_BTF_ID | PTR_TRUSTED | PTR_MAYBE_NULL. This
makes the verifier to check programs and ensure that they properly check
the pointer. The programs should check if the pointer is null before
accessing the pointed memory.

The implementer of a struct_ops type should annotate the arguments that can
be null. The implementer should define a stub function (empty) as a
placeholder for each defined operator. The name of a stub function should
be in the pattern "__". For example, for
test_maybe_null of struct bpf_testmod_ops, it's stub function name should
be "bpf_testmod_ops__test_maybe_null". You mark an argument nullable by
suffixing the argument name with "__nullable" at the stub function.

Since we already has stub functions for kCFI, we just reuse these stub
functions with the naming convention mentioned earlier. These stub
functions with the naming convention is only required if there are nullable
arguments to annotate. For functions having not nullable arguments, stub
functions are not necessary for the purpose of this patch.

This patch will prepare a list of struct bpf_ctx_arg_aux, aka arg_info, for
each member field of a struct_ops type.  "arg_info" will be assigned to
"prog->aux->ctx_arg_info" of BPF struct_ops programs in
check_struct_ops_btf_id() so that it can be used by btf_ctx_access() later
to set reg_type properly for the verifier.

Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240209023750.1153905-4-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau

bpf: Remove an unnecessary check.

2024-02-05T18:25:08+00:00

The "i" here is always equal to "btf_type_vlen(t)" since
the "for_each_member()" loop never breaks.

Signed-off-by: Kui-Feng Lee 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/20240203055119.2235598-1-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau

bpf: Fix error checks against bpf_get_btf_vmlinux().

2024-01-26T04:49:59+00:00

In bpf_struct_ops_map_alloc, it needs to check for NULL in the returned
pointer of bpf_get_btf_vmlinux() when CONFIG_DEBUG_INFO_BTF is not set.
ENOTSUPP is used to preserve the same behavior before the
struct_ops kmod support.

In the function check_struct_ops_btf_id(), instead of redoing the
bpf_get_btf_vmlinux() that has already been done in syscall.c, the fix
here is to check for prog->aux->attach_btf_id.
BPF_PROG_TYPE_STRUCT_OPS must require attach_btf_id and syscall.c
guarantees a valid attach_btf as long as attach_btf_id is set.
When attach_btf_id is not set, this patch returns -ENOTSUPP
because it is what the selftest in test_libbpf_probe_prog_types()
and libbpf_probes.c are expecting for feature probing purpose.

Changes from v1:

 - Remove an unnecessary NULL check in check_struct_ops_btf_id()

Reported-by: syzbot+88f0aafe5f950d7489d7@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/00000000000040d68a060fc8db8c@google.com/
Reported-by: syzbot+1336f3d4b10bcda75b89@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/00000000000026353b060fc21c07@google.com/
Fixes: fcc2c1fb0651 ("bpf: pass attached BTF to the bpf_struct_ops subsystem")
Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240126023113.1379504-1-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau

bpf, net: switch to dynamic registration

2024-01-24T01:12:46+00:00

Replace the static list of struct_ops types with per-btf struct_ops_tab to
enable dynamic registration.

Both bpf_dummy_ops and bpf_tcp_ca now utilize the registration function
instead of being listed in bpf_struct_ops_types.h.

Cc: netdev@vger.kernel.org
Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240119225005.668602-12-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau

bpf: validate value_type

2024-01-24T00:37:45+00:00

A value_type should consist of three components: refcnt, state, and data.
refcnt and state has been move to struct bpf_struct_ops_common_value to
make it easier to check the value type.

Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240119225005.668602-11-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau