This is a note to let you know that I've just added the patch titled

MIPS: Guard against any partial write attempt with PTRACE_SETREGSET

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: mips-guard-against-any-partial-write-attempt-with-ptrace_setregset.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From dc24d0edf33c3e15099688b6bbdf7bdc24bf6e91 Mon Sep 17 00:00:00 2001

From: "Maciej W. Rozycki" macro@mips.com Date: Mon, 11 Dec 2017 22:52:15 +0000 Subject: MIPS: Guard against any partial write attempt with PTRACE_SETREGSET

From: Maciej W. Rozycki macro@mips.com

commit dc24d0edf33c3e15099688b6bbdf7bdc24bf6e91 upstream.

Complement commit d614fd58a283 ("mips/ptrace: Preserve previous registers for short regset write") and ensure that no partial register write attempt is made with PTRACE_SETREGSET, as we do not preinitialize any temporaries used to hold incoming register data and consequently random data could be written.

It is the responsibility of the caller, such as `ptrace_regset', to arrange for writes to span whole registers only, so here we only assert that it has indeed happened.

Signed-off-by: Maciej W. Rozycki macro@mips.com Fixes: 72b22bbad1e7 ("MIPS: Don't assume 64-bit FP registers for FP regset") Cc: James Hogan james.hogan@mips.com Cc: Paul Burton Paul.Burton@mips.com Cc: Alex Smith alex@alex-smith.me.uk Cc: Dave Martin Dave.Martin@arm.com Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/17926/ Signed-off-by: Ralf Baechle ralf@linux-mips.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/mips/kernel/ptrace.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -536,7 +536,15 @@ static int fpr_set_msa(struct task_struc return 0; }

-/* Copy the supplied NT_PRFPREG buffer to the floating-point context. */ +/* + * Copy the supplied NT_PRFPREG buffer to the floating-point context. + * + * We optimize for the case where `count % sizeof(elf_fpreg_t) == 0', + * which is supposed to have been guaranteed by the kernel before + * calling us, e.g. in `ptrace_regset'. We enforce that requirement, + * so that we can safely avoid preinitializing temporaries for + * partial register writes. + */ static int fpr_set(struct task_struct *target, const struct user_regset *regset, unsigned int pos, unsigned int count, @@ -544,6 +552,8 @@ static int fpr_set(struct task_struct *t { int err;

+ BUG_ON(count % sizeof(elf_fpreg_t)); + /* XXX fcr31 */

init_fp_ctx(target);

Patches currently in stable-queue which might be from macro@mips.com are

queue-4.9/mips-consistently-handle-buffer-counter-with-ptrace_setregset.patch queue-4.9/mips-disallow-outsized-ptrace_setregset-nt_prfpreg-regset-accesses.patch queue-4.9/mips-guard-against-any-partial-write-attempt-with-ptrace_setregset.patch queue-4.9/mips-also-verify-sizeof-elf_fpreg_t-with-ptrace_setregset.patch queue-4.9/mips-factor-out-nt_prfpreg-regset-access-helpers.patch queue-4.9/mips-validate-pr_set_fp_mode-prctl-2-requests-against-the-abi-of-the-task.patch queue-4.9/mips-fix-an-fcsr-access-api-regression-with-nt_prfpreg-and-msa.patch