[PATCH bpf 0/2] bpf: fix a verifier issue when assigning 32bit reg states to 64bit ones

[Yonghong Song <yhs@fb.com>]

Commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking")
added 32bit register states to verifier for explicit ALU32 bounds
tracking. When assigning 32bit register states to 64bit register states,
if 32bit register is a constant value of 0, the 64bit register smax_val
will get U32_MAX(0xffffFFFF). Such an inprecise information may impact
downward verification. Patch #1 has detailed explanation of the program
and how to fix it. Patch #2 provides a verifier test to cover the change.

Yonghong Song (2):
  bpf: fix a verifier issue when assigning 32bit reg states to 64bit
  tools/bpf: add a verifier test for assigning 32bit reg states to 64bit

 kernel/bpf/verifier.c                         |  3 +++
 tools/testing/selftests/bpf/verifier/bounds.c | 22 +++++++++++++++++++
 2 files changed, 25 insertions(+)

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2.24.1