Commit 34904582 authored by Brahmajit Das's avatar Brahmajit Das Committed by Alexei Starovoitov
Browse files

bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer 



In check_alu_op(), the verifier currently calls check_reg_arg() and
adjust_scalar_min_max_vals() unconditionally for BPF_NEG operations.
However, if the destination register holds a pointer, these scalar
adjustments are unnecessary and potentially incorrect.

This patch adds a check to skip the adjustment logic when the destination
register contains a pointer.

Reported-by: default avatar <syzbot+d36d5ae81e1b0a53ef58@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=d36d5ae81e1b0a53ef58


Fixes: aced1325 ("bpf: Add range tracking for BPF_NEG")
Suggested-by: default avatarKaFai Wan <kafai.wan@linux.dev>
Suggested-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarBrahmajit Das <listout@listout.xyz>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251001191739.2323644-2-listout@listout.xyz


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 0c342bfc

kernel/bpf/verifier.c

+2 −1
Original line number Diff line number Diff line
@@ -15645,7 +15645,8 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) 
		}









		/* check dest operand */









		if (opcode == BPF_NEG) {









		if (opcode == BPF_NEG &&









		    regs[insn->dst_reg].type == SCALAR_VALUE) {









			err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);









			err = err ?: adjust_scalar_min_max_vals(env, insn,









							 &regs[insn->dst_reg],