diff options
| author | Hao Sun <sunhao.th@gmail.com> | 2023-01-04 09:47:09 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-02-09 11:26:48 +0100 |
| commit | 6e2fac197de2c4c041bdd8982cffb104689113f1 (patch) | |
| tree | 046c7629e9057b0a8774a448a6deb9104ee9fecd /kernel/bpf | |
| parent | 46c9088cabd4d0469fdb61ac2a9c5003057fe94d (diff) | |
bpf: Skip invalid kfunc call in backtrack_insn
commit d3178e8a434b58678d99257c0387810a24042fb6 upstream.
The verifier skips invalid kfunc call in check_kfunc_call(), which
would be captured in fixup_kfunc_call() if such insn is not eliminated
by dead code elimination. However, this can lead to the following
warning in backtrack_insn(), also see [1]:
------------[ cut here ]------------
verifier backtracking bug
WARNING: CPU: 6 PID: 8646 at kernel/bpf/verifier.c:2756 backtrack_insn
kernel/bpf/verifier.c:2756
__mark_chain_precision kernel/bpf/verifier.c:3065
mark_chain_precision kernel/bpf/verifier.c:3165
adjust_reg_min_max_vals kernel/bpf/verifier.c:10715
check_alu_op kernel/bpf/verifier.c:10928
do_check kernel/bpf/verifier.c:13821 [inline]
do_check_common kernel/bpf/verifier.c:16289
[...]
So make backtracking conservative with this by returning ENOTSUPP.
[1] https://lore.kernel.org/bpf/CACkBjsaXNceR8ZjkLG=dT3P=4A8SBsg0Z5h5PWLryF5=ghKq=g@mail.gmail.com/
Reported-by: syzbot+4da3ff23081bafe74fc2@syzkaller.appspotmail.com
Signed-off-by: Hao Sun <sunhao.th@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20230104014709.9375-1-sunhao.th@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e7ca52dd55f3..1c95d97e7aa5 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2261,6 +2261,12 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, if (opcode == BPF_CALL) { if (insn->src_reg == BPF_PSEUDO_CALL) return -ENOTSUPP; + /* kfunc with imm==0 is invalid and fixup_kfunc_call will + * catch this error later. Make backtracking conservative + * with ENOTSUPP. + */ + if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL && insn->imm == 0) + return -ENOTSUPP; /* regular helper call sets R0 */ *reg_mask &= ~1; if (*reg_mask & 0x3f) { |