This patch set refactors kernel/bpf/verifier.c to use type-agnostic, generic overflow-check helpers defined in include/linux/overflow.h to check for addition and subtraction overflow, and drop the signed_*_overflows() helpers we currently have in kernel/bpf/verifier.c; with a fix for overflow check in adjust_jmp_off() in patch 1. There should be no functional change in how the verifier works and the main motivation is to make future refactoring[1] easier. While check_mul_overflow() also exists and could potentially replace what we have in scalar*_min_max_mul(), it does not help with refactoring and would either change how the verifier works (e.g. lifting restriction on umax<=U32_MAX and u32_max<=U16_MAX) or make the code slightly harder to read, so it is left for future endeavour. Changes from v2 <https://lore.kernel.org/r/20240701055907.82481-1-shung-hsi.yu@xxxxxxxx> - add fix for 5337ac4c9b80 ("bpf: Fix the corner case with may_goto and jump to the 1st insn.") to correct the overflow check for general jump instructions - adapt to changes in commit 5337ac4c9b80 ("bpf: Fix the corner case with may_goto and jump to the 1st insn.") - refactor in adjust_jmp_off() as well and remove signed_add16_overflow() Changes from v1 <https://lore.kernel.org/r/20240623070324.12634-1-shung-hsi.yu@xxxxxxxx>: - use pointers to values in dst_reg directly as the sum/diff pointer and remove the else branch (Jiri) - change local variables to be dst_reg pointers instead of src_reg values - include comparison of generated assembly before & after the change (Alexei) 1: https://github.com/kernel-patches/bpf/pull/7205/commits Shung-Hsi Yu (3): bpf: fix overflow check in adjust_jmp_off() bpf: use check_add_overflow() to check for addition overflows bpf: use check_sub_overflow() to check for subtraction overflows kernel/bpf/verifier.c | 171 ++++++++++++------------------------------ 1 file changed, 48 insertions(+), 123 deletions(-) -- 2.45.2
