On Wed, Dec 02, 2020 at 05:51:16PM +0900, Masami Hiramatsu wrote:
> Since the insn.prefixes.nbytes can be bigger than the size of
> insn.prefixes.bytes[] when a same prefix is repeated, we have to
> check whether the insn.prefixes.bytes[i] != 0 and i < 4 instead
> of insn.prefixes.nbytes.
>
> Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove
> uprobes breakpoints")
> Cc: sta...@vger.kernel.org
> Reported-by: Kees Cook <keesc...@chromium.org>
This should probably be:
Reported-by: syzbot+9b64b619f10f19d19...@syzkaller.appspotmail.com
Debugged-by: Kees Cook <keesc...@chromium.org>
> Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
> ---
> arch/x86/kernel/uprobes.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index 3fdaa042823d..bb3ea3705b99 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -257,7 +257,7 @@ static bool is_prefix_bad(struct insn *insn)
> {
> int i;
>
> - for (i = 0; i < insn->prefixes.nbytes; i++) {
> + for (i = 0; insn->prefixes.bytes[i] && i < 4; i++) {
> insn_attr_t attr;
>
> attr = inat_get_opcode_attribute(insn->prefixes.bytes[i]);
> @@ -746,7 +746,7 @@ static int branch_setup_xol_ops(struct arch_uprobe
> *auprobe, struct insn *insn)
> * Intel and AMD behavior differ in 64-bit mode: Intel ignores 66
> prefix.
> * No one uses these insns, reject any branch insns with such prefix.
> */
> - for (i = 0; i < insn->prefixes.nbytes; i++) {
> + for (i = 0; insn->prefixes.bytes[i] && i < 4; i++) {
> if (insn->prefixes.bytes[i] == 0x66)
> return -ENOTSUPP;
> }
>
--
Kees Cook
