bpf: fix 64-bit divide

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>

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 4139a0f8b558e4e7db4f79adbd353c97c7fda553..54f0e7fcd0e288b4506fab80091dcc39069ae422 100644 (file)
--- 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;