[PATCH v2 6/6] MIPS: Disallow outsized PTRACE_SETREGSET NT_PRFPREG regset accesses

[Maciej W. Rozycki]

Complement commit c23b3d1a5311 ("MIPS: ptrace: Change GP regset to use 
correct core dump register layout") and also reject outsized 
PTRACE_SETREGSET requests to the NT_PRFPREG regset, like with the 
NT_PRSTATUS regset.

Cc: stable@xxxxxxxxxxxxxxx # v3.17+
Fixes: c23b3d1a5311 ("MIPS: ptrace: Change GP regset to use correct core dump register layout")
Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxx>
---

Changes from v1:

- regenerated.

---
 arch/mips/kernel/ptrace.c |    3 +++
 1 file changed, 3 insertions(+)

linux-mips-nt-prfpreg-size.diff
Index: linux-sfr-test/arch/mips/kernel/ptrace.c
===================================================================
--- linux-sfr-test.orig/arch/mips/kernel/ptrace.c	2017-12-08 16:22:08.062741000 +0000
+++ linux-sfr-test/arch/mips/kernel/ptrace.c	2017-12-08 16:22:17.727811000 +0000
@@ -541,6 +541,9 @@ static int fpr_set(struct task_struct *t
 
 	BUG_ON(count % sizeof(elf_fpreg_t));
 
+	if (pos + count > sizeof(elf_fpregset_t))
+		return -EIO;
+
 	init_fp_ctx(target);
 
 	if (sizeof(target->thread.fpu.fpr[0]) == sizeof(elf_fpreg_t))