Commit 2611e241 authored Apr 27, 2015 by Alexei Starovoitov Committed by Sasha Levin May 17, 2015

bpf: fix 64-bit divide



[ Upstream commit 876a7ae65b86d8cec8efe7d15d050ac61116874e ]

ALU64_DIV instruction should be dividing 64-bit by 64-bit,
whereas do_div() does 64-bit by 32-bit divide.
x64 and arm64 JITs correctly implement 64 by 64 unsigned divide.
llvm BPF backend emits code assuming that ALU64_DIV does 64 by 64.

Fixes: 89aa075832b0 ("net: sock: allow eBPF programs to be attached to sockets")
Reported-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

parent 7f1a6ae7

kernel/bpf/core.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -357,8 +357,8 @@ select_insn:
		ALU64_MOD_X:
		if (unlikely(SRC == 0))
		return 0;
		tmp = DST;
		DST = do_div(tmp, SRC);
		div64_u64_rem(DST, SRC, &tmp);
		DST = tmp;
		CONT;
		ALU_MOD_X:
		if (unlikely(SRC == 0))
		@@ -367,8 +367,8 @@ select_insn:
		DST = do_div(tmp, (u32) SRC);
		CONT;
		ALU64_MOD_K:
		tmp = DST;
		DST = do_div(tmp, IMM);
		div64_u64_rem(DST, IMM, &tmp);
		DST = tmp;
		CONT;
		ALU_MOD_K:
		tmp = (u32) DST;
		@@ -377,7 +377,7 @@ select_insn:
		ALU64_DIV_X:
		if (unlikely(SRC == 0))
		return 0;
		do_div(DST, SRC);
		DST = div64_u64(DST, SRC);
		CONT;
		ALU_DIV_X:
		if (unlikely(SRC == 0))
		@@ -387,7 +387,7 @@ select_insn:
		DST = (u32) tmp;
		CONT;
		ALU64_DIV_K:
		do_div(DST, IMM);
		DST = div64_u64(DST, IMM);
		CONT;
		ALU_DIV_K:
		tmp = (u32) DST;