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    Subject[ 097/108] net: bpf_jit: fix BPF_S_LDX_B_MSH compilation
    3.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------


    From: Eric Dumazet <eric.dumazet@gmail.com>

    [ Upstream commit dc72d99dabb870ca5bd6d9fff674be853bb4a88d ]

    Matt Evans spotted that x86 bpf_jit was incorrectly handling negative
    constant offsets in BPF_S_LDX_B_MSH instruction.

    We need to abort JIT compilation like we do in common_load so that
    filter uses the interpreter code and can call __load_pointer()

    Reference: http://lists.openwall.net/netdev/2011/07/19/11

    Thanks to Indan Zupancic to bring back this issue.

    Reported-by: Matt Evans <matt@ozlabs.org>
    Reported-by: Indan Zupancic <indan@nul.nu>
    Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/net/bpf_jit_comp.c | 14 +++++---------
    1 file changed, 5 insertions(+), 9 deletions(-)

    --- a/arch/x86/net/bpf_jit_comp.c
    +++ b/arch/x86/net/bpf_jit_comp.c
    @@ -475,8 +475,10 @@ void bpf_jit_compile(struct sk_filter *f
    case BPF_S_LD_W_ABS:
    func = sk_load_word;
    common_load: seen |= SEEN_DATAREF;
    - if ((int)K < 0)
    + if ((int)K < 0) {
    + /* Abort the JIT because __load_pointer() is needed. */
    goto out;
    + }
    t_offset = func - (image + addrs[i]);
    EMIT1_off32(0xbe, K); /* mov imm32,%esi */
    EMIT1_off32(0xe8, t_offset); /* call */
    @@ -489,14 +491,8 @@ common_load: seen |= SEEN_DATAREF;
    goto common_load;
    case BPF_S_LDX_B_MSH:
    if ((int)K < 0) {
    - if (pc_ret0 > 0) {
    - /* addrs[pc_ret0 - 1] is the start address */
    - EMIT_JMP(addrs[pc_ret0 - 1] - addrs[i]);
    - break;
    - }
    - CLEAR_A();
    - EMIT_JMP(cleanup_addr - addrs[i]);
    - break;
    + /* Abort the JIT because __load_pointer() is needed. */
    + goto out;
    }
    seen |= SEEN_DATAREF | SEEN_XREG;
    t_offset = sk_load_byte_msh - (image + addrs[i]);



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