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bpf: fix divides by zero

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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: bd4cf0ed331a ("net: filter: rework/optimize internal BPF interpreter's instruction set")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eric Dumazet 2018-01-12 17:43:23 -08:00 committed by Alexei Starovoitov
parent 8155aedf51
commit c366287ebd
1 changed files with 2 additions and 2 deletions
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4
kernel/bpf/core.c
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@ -956,7 +956,7 @@ select_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);
@ -975,7 +975,7 @@ select_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);