[PATCH 4.0 01/72] bpf: fix 64-bit divide

Greg Kroah-Hartman
2015-05-11T17:55:42Z

From: Alexei Starovoitov <ast@plumgrid.com>

[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/core.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -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;