From: Daniel Borkmann daniel@iogearbox.net
commit ee114dd64c0071500345439fc79dd5e0f9d106ed upstream.
Fix incorrect is_branch{32,64}_taken() analysis for the jsgt case. The return code for both will tell the caller whether a given conditional jump is taken or not, e.g. 1 means branch will be taken [for the involved registers] and the goto target will be executed, 0 means branch will not be taken and instead we fall-through to the next insn, and last but not least a -1 denotes that it is not known at verification time whether a branch will be taken or not. Now while the jsgt has the branch-taken case correct with reg->s32_min_value > sval, the branch-not-taken case is off-by-one when testing for reg->s32_max_value < sval since the branch will also be taken for reg->s32_max_value == sval. The jgt branch analysis, for example, gets this right.
Fixes: 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") Fixes: 4f7b3e82589e ("bpf: improve verifier branch analysis") Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: John Fastabend john.fastabend@gmail.com Acked-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/verifier.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6822,7 +6822,7 @@ static int is_branch32_taken(struct bpf_ case BPF_JSGT: if (reg->s32_min_value > sval) return 1; - else if (reg->s32_max_value < sval) + else if (reg->s32_max_value <= sval) return 0; break; case BPF_JLT: @@ -6895,7 +6895,7 @@ static int is_branch64_taken(struct bpf_ case BPF_JSGT: if (reg->smin_value > sval) return 1; - else if (reg->smax_value < sval) + else if (reg->smax_value <= sval) return 0; break; case BPF_JLT: