In the Linux kernel, the following vulnerability has been resolved: bpf: Reset register ID for...

In the Linux kernel, the following vulnerability has been resolved:

bpf: Reset register ID for BPF_END value tracking

When a register undergoes a BPF_END (byte swap) operation, its scalar value is mutated in-place. If this register previously shared a scalar ID with another register (e.g., after an r1 = r0 assignment), this tie must be broken.

Currently, the verifier misses resetting dst_reg->id to 0 for BPF_END. Consequently, if a conditional jump checks the swapped register, the verifier incorrectly propagates the learned bounds to the linked register, leading to false confidence in the linked register's value and potentially allowing out-of-bounds memory accesses.

Fix this by explicitly resetting dst_reg->id to 0 in the BPF_END case to break the scalar tie, similar to how BPF_NEG handles it via __mark_reg_known.