mirror of
https://github.com/torvalds/linux.git
synced 2025-12-07 20:06:24 +00:00
df4b1eebd8
Luis Gerhorst says:
====================
bpf: Fix and test aux usage after do_check_insn()
Fix cur_aux()->nospec_result test after do_check_insn() referring to the
to-be-analyzed (potentially unsafe) instruction, not the
already-analyzed (safe) instruction. This might allow a unsafe insn to
slip through on a speculative path. Create some tests from the
reproducer [1].
Commit d6f1c85f22 ("bpf: Fall back to nospec for Spectre v1") should
not be in any stable kernel yet, therefore bpf-next should suffice.
[1] https://lore.kernel.org/bpf/685b3c1b.050a0220.2303ee.0010.GAE@google.com/
Changes since v2:
- Use insn_aux variable instead of introducing prev_aux() as suggested
by Eduard (and therefore also drop patch 1)
- v2: https://lore.kernel.org/bpf/20250628145016.784256-1-luis.gerhorst@fau.de/
Changes since v1:
- Fix compiler error due to missed rename of prev_insn_idx in first
patch
- v1: https://lore.kernel.org/bpf/20250628125927.763088-1-luis.gerhorst@fau.de/
Changes since RFC:
- Introduce prev_aux() as suggested by Alexei. For this, we must move
the env->prev_insn_idx assignment to happen directly after
do_check_insn(), for which I have created a separate commit. This
patch could be simplified by using a local prev_aux variable as
sugested by Eduard, but I figured one might find the new
assignment-strategy easier to understand (before, prev_insn_idx and
env->prev_insn_idx were out-of-sync for the latter part of the loop).
Also, like this we do not have an additional prev_* variable that must
be kept in-sync and the local variable's usage (old prev_insn_idx, new
tmp) is much more local. If you think it would be better to not take
the risk and keep the fix simple by just introducing the prev_aux
variable, let me know.
- Change WARN_ON_ONCE() to verifier_bug_if() as suggested by Alexei
- Change assertion to check instruction is BPF_JMP[32] as suggested by
Eduard
- RFC: https://lore.kernel.org/bpf/8734bmoemx.fsf@fau.de/
====================
Link: https://patch.msgid.link/20250705190908.1756862-1-luis.gerhorst@fau.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.