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Commit 46060778 authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
Browse files

bpf: fix divides by zero 



[ upstream commit c366287ebd698ef5e3de300d90cd62ee9ee7373e ]

Divides by zero are not nice, lets avoid them if possible.

Also do_div() seems not needed when dealing with 32bit operands,
but this seems a minor detail.

Fixes: bd4cf0ed ("net: filter: rework/optimize internal BPF interpreter's instruction set")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarsyzbot <syzkaller@googlegroups.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5cb917aa

kernel/bpf/core.c

+2 −2
Original line number Original line Diff line number Diff line
@@ -642,7 +642,7 @@ static unsigned int __bpf_prog_run(void *ctx, const struct bpf_insn *insn) 
		DST = tmp;

		DST = tmp;

		CONT;

		CONT;

	ALU_MOD_X:

	ALU_MOD_X:

		if (unlikely(SRC == 0))

		if (unlikely((u32)SRC == 0))

			return 0;

			return 0;

		tmp = (u32) DST;

		tmp = (u32) DST;

		DST = do_div(tmp, (u32) SRC);

		DST = do_div(tmp, (u32) SRC);
@@ -661,7 +661,7 @@ static unsigned int __bpf_prog_run(void *ctx, const struct bpf_insn *insn) 
		DST = div64_u64(DST, SRC);

		DST = div64_u64(DST, SRC);

		CONT;

		CONT;

	ALU_DIV_X:

	ALU_DIV_X:

		if (unlikely(SRC == 0))

		if (unlikely((u32)SRC == 0))

			return 0;

			return 0;

		tmp = (u32) DST;

		tmp = (u32) DST;

		do_div(tmp, (u32) SRC);

		do_div(tmp, (u32) SRC);