[PATCH 4.14 v2 0/4] BPF fixes for CVE-2021-3444 and CVE-2021-3600

Edward Liaw
2023-02-22T19:29:43Z

Thadeu Lima de Souza Cascardo originally sent this patch but it failed to
merge because of a compilation error:

https://lore.kernel.org/bpf/20210830183211.339054-1-cascardo@canonical.com/T/

v2:
Removed redefinition of tmp to fix compilation with CONFIG_BPF_JIT_ALWAYS_ON
enabled.

-Edward

==

The upstream changes necessary to fix these CVEs rely on the presence of JMP32,
which is not a small backport and brings its own potential set of necessary
follow-ups.

Daniel Borkmann, John Fastabend and Alexei Starovoitov came up with a fix
involving the use of the AX register.

This has been tested against the test_verifier in 4.14.y tree and some tests
specific to the two referred CVEs. The test_bpf module was also tested.

Daniel Borkmann (4):
bpf: Do not use ax register in interpreter on div/mod
bpf: fix subprog verifier bypass by div/mod by 0 exception
bpf: Fix 32 bit src register truncation on div/mod
bpf: Fix truncation handling for mod32 dst reg wrt zero

include/linux/filter.h | 24 ++++++++++++++++++++++++
kernel/bpf/core.c | 39 ++++++++++++++-------------------------
kernel/bpf/verifier.c | 39 +++++++++++++++++++++++++++++++--------
net/core/filter.c | 9 ++++++++-
4 files changed, 77 insertions(+), 34 deletions(-)

base-commit: a8ad60f2af5884921167e8cede5784c7849884b2
--
2.39.2.637.g21b0678d19-goog