From: Daniel Borkmann daniel@iogearbox.net
[ no upstream commit ]
Fix incorrect bounds tracking for RSH opcode. Commit f23cc643f9ba ("bpf: fix range arithmetic for bpf map access") had a wrong assumption about min/max bounds. The new dst_reg->min_value needs to be derived by right shifting the max_val bounds, not min_val, and likewise new dst_reg->max_value needs to be derived by right shifting the min_val bounds, not max_val. Later stable kernels than 4.9 are not affected since bounds tracking was overall reworked and they already track this similarly as in the fix.
Fixes: f23cc643f9ba ("bpf: fix range arithmetic for bpf map access") Reported-by: Ryota Shiga (Flatt Security) Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: John Fastabend john.fastabend@gmail.com Cc: Josef Bacik jbacik@fb.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/verifier.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1732,12 +1732,11 @@ static void adjust_reg_min_max_vals(stru * unsigned shift, so make the appropriate casts. */ if (min_val < 0 || dst_reg->min_value < 0) - dst_reg->min_value = BPF_REGISTER_MIN_RANGE; + reset_reg_range_values(regs, insn->dst_reg); else - dst_reg->min_value = - (u64)(dst_reg->min_value) >> min_val; + dst_reg->min_value = (u64)(dst_reg->min_value) >> max_val; if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) - dst_reg->max_value >>= max_val; + dst_reg->max_value >>= min_val; break; default: reset_reg_range_values(regs, insn->dst_reg);