From: Shung-Hsi Yu <shung-hsi.yu@suse.com> stable inclusion from stable-v5.10.202 commit 5fb8ec5943b179e7486badf96a92c17fef16941b category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB4BCM Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 291d044fd51f8484066300ee42afecf8c8db7b3a upstream. BPF_END and BPF_NEG has a different specification for the source bit in the opcode compared to other ALU/ALU64 instructions, and is either reserved or use to specify the byte swap endianness. In both cases the source bit does not encode source operand location, and src_reg is a reserved field. backtrack_insn() currently does not differentiate BPF_END and BPF_NEG from other ALU/ALU64 instructions, which leads to r0 being incorrectly marked as precise when processing BPF_ALU | BPF_TO_BE | BPF_END instructions. This commit teaches backtrack_insn() to correctly mark precision for such case. While precise tracking of BPF_NEG and other BPF_END instructions are correct and does not need fixing, this commit opt to process all BPF_NEG and BPF_END instructions within the same if-clause to better align with current convention used in the verifier (e.g. check_alu_op). Fixes: b5dc0163d8fd ("bpf: precise scalar_value tracking") Cc: stable@vger.kernel.org Reported-by: Mohamed Mahmoud <mmahmoud@redhat.com> Closes: https://lore.kernel.org/r/87jzrrwptf.fsf@toke.dk Tested-by: Toke Høiland-Jørgensen <toke@redhat.com> Tested-by: Tao Lyu <tao.lyu@epfl.ch> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Link: https://lore.kernel.org/r/20231102053913.12004-2-shung-hsi.yu@suse.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Wang Hai <wanghai38@huawei.com> Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/verifier.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7473544d7e04..74e9109b4c18 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1890,7 +1890,12 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, if (class == BPF_ALU || class == BPF_ALU64) { if (!(*reg_mask & dreg)) return 0; - if (opcode == BPF_MOV) { + if (opcode == BPF_END || opcode == BPF_NEG) { + /* sreg is reserved and unused + * dreg still need precision before this insn + */ + return 0; + } else if (opcode == BPF_MOV) { if (BPF_SRC(insn->code) == BPF_X) { /* dreg = sreg * dreg needs precision after this insn -- 2.34.1