Patch "MIPS: Consistently handle buffer counter with PTRACE_SETREGSET" has been added to the 4.9-stable tree

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

MIPS: Consistently handle buffer counter 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;a=summary

The filename of the patch is:
mips-consistently-handle-buffer-counter-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 <[email protected]> know about it.

From: "Maciej W. Rozycki" <[email protected]>
Date: Mon, 11 Dec 2017 22:53:14 +0000
Subject: MIPS: Consistently handle buffer counter with PTRACE_SETREGSET

From: Maciej W. Rozycki <[email protected]>

commit 80b3ffce0196ea50068885d085ff981e4b8396f4 upstream.

Update commit d614fd58a283 ("mips/ptrace: Preserve previous registers for short regset write") bug and consistently consume all data supplied to `fpr_set_msa' with the ptrace(2) PTRACE_SETREGSET request, such that a zero data buffer counter is returned where insufficient data has been given to fill a whole number of FP general registers.

In reality this is not going to happen, as the caller is supposed to only supply data covering a whole number of registers and it is verified in ptrace_regset' and again asserted in fpr_set', however structuring code such that the presence of trailing partial FP general register data causes `fpr_set_msa' to return with a non-zero data buffer counter makes it appear that this trailing data will be used if there are subsequent writes made to FP registers, which is going to be the case with the FCSR once the missing write to that register has been fixed.

Patchwork: https://patchwork.linux-mips.org/patch/17927/

---
 arch/mips/kernel/ptrace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -524,7 +524,7 @@ static int fpr_set_msa(struct task_struc
 	int err;
 
 	BUILD_BUG_ON(sizeof(fpr_val) != sizeof(elf_fpreg_t));
-	for (i = 0; i < NUM_FPU_REGS && *count >= sizeof(elf_fpreg_t); i++) {
+	for (i = 0; i < NUM_FPU_REGS && *count > 0; i++) {
 		err = user_regset_copyin(pos, count, kbuf, ubuf,
 					 &fpr_val, i * sizeof(elf_fpreg_t),
 					 (i + 1) * sizeof(elf_fpreg_t));

Patches currently in stable-queue which might be from [email protected] 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