Bpf rdonly cast void #9176
Open
Bpf rdonly cast void #9176
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
eddyz87
force-pushed
the
bpf-rdonly-cast-void
branch
2 times, most recently
from
a1661f7 to
0f4860e
Compare
kernel-patches-daemon-bpf
bot
force-pushed
the
bpf-next_base
branch
from
4b5a6fc to
a2a54b8
Compare
eddyz87
force-pushed
the
bpf-rdonly-cast-void
branch
from
0f4860e to
a523e82
Compare
This reverts commit e800ac5.
This reverts commit 9734e25.
This commit adds a kernel side enum for use in conjucntion with BTF
CO-RE bpf_core_enum_value_exists. The goal of the enum is to assist
with available BPF features detection. Intended usage looks as
follows:
if (bpf_core_enum_value_exists(enum bpf_features, BPF_FEAT_<f>))
... use feature f ...
Signed-off-by: Eduard Zingerman <[email protected]>
Introduce support for `bpf_rdonly_cast(v, 0)`, which casts the value `v` to an untyped, untrusted pointer, logically similar to a `void *`. The memory pointed to by such a pointer is treated as read-only. As with other untrusted pointers, memory access violations on loads return zero instead of causing a fault. Technically: - The resulting pointer is represented as a register of type `PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED` with size zero. - Offsets within such pointers are not tracked. - Same load instructions are allowed to have both `PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED` and `PTR_TO_BTF_ID` as the base pointer types. In such cases, `bpf_insn_aux_data->ptr_type` is considered the weaker of the two: `PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED`. The following constraints apply to the new pointer type: - can be used as a base for LDX instructions; - can't be used as a base for ST/STX or atomic instructions; - can't be used as parameter for kfuncs or helpers. These constraints are enforced by existing handling of `MEM_RDONLY` flag and `PTR_TO_MEM` of size zero. Suggested-by: Alexei Starovoitov <[email protected]> Suggested-by: Andrii Nakryiko <[email protected]> Signed-off-by: Eduard Zingerman <[email protected]>
The following cases are tested: - it is ok to load memory at any offset from rdonly_untrusted_mem; - rdonly_untrusted_mem offset/bounds are not tracked; - writes into rdonly_untrusted_mem are forbidden; - atomic operations on rdonly_untrusted_mem are forbidden; - rdonly_untrusted_mem can't be passed as a memory argument of a helper of kfunc; - it is ok to use PTR_TO_MEM and PTR_TO_BTF_ID in a same load instruction. Signed-off-by: Eduard Zingerman <[email protected]>
eddyz87
force-pushed
the
bpf-rdonly-cast-void
branch
from
a523e82 to
6f564cf
Compare
kernel-patches-daemon-bpf
bot
force-pushed
the
bpf-next_base
branch
from
a2a54b8 to
2e3dd89
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
No description provided.