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    Subject[PATCH 5.4 54/54] x86/insn-eval: Use new for_each_insn_prefix() macro to loop over prefixes bytes
    Date
    From: Masami Hiramatsu <mhiramat@kernel.org>

    commit 12cb908a11b2544b5f53e9af856e6b6a90ed5533 upstream

    Since insn.prefixes.nbytes can be bigger than the size of
    insn.prefixes.bytes[] when a prefix is repeated, the proper check must
    be

    insn.prefixes.bytes[i] != 0 and i < 4

    instead of using insn.prefixes.nbytes. Use the new
    for_each_insn_prefix() macro which does it correctly.

    Debugged by Kees Cook <keescook@chromium.org>.

    [ bp: Massage commit message. ]

    Fixes: 32d0b95300db ("x86/insn-eval: Add utility functions to get segment selector")
    Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com
    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Cc: stable@vger.kernel.org
    Link: https://lkml.kernel.org/r/160697104969.3146288.16329307586428270032.stgit@devnote2
    [sudip: adjust context]
    Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/lib/insn-eval.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- a/arch/x86/lib/insn-eval.c
    +++ b/arch/x86/lib/insn-eval.c
    @@ -70,14 +70,15 @@ static int get_seg_reg_override_idx(stru
    {
    int idx = INAT_SEG_REG_DEFAULT;
    int num_overrides = 0, i;
    + insn_byte_t p;

    insn_get_prefixes(insn);

    /* Look for any segment override prefixes. */
    - for (i = 0; i < insn->prefixes.nbytes; i++) {
    + for_each_insn_prefix(insn, i, p) {
    insn_attr_t attr;

    - attr = inat_get_opcode_attribute(insn->prefixes.bytes[i]);
    + attr = inat_get_opcode_attribute(p);
    switch (attr) {
    case INAT_MAKE_PREFIX(INAT_PFX_CS):
    idx = INAT_SEG_REG_CS;

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