From: Maciej W. Rozycki Date: Mon, 11 Dec 2017 22:52:15 +0000 (+0000) Subject: MIPS: Guard against any partial write attempt with PTRACE_SETREGSET X-Git-Tag: v3.18.92~36 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=80aaed846ef9d812fde6eea2bf0a6966e325d862;p=thirdparty%2Fkernel%2Fstable.git MIPS: Guard against any partial write attempt with PTRACE_SETREGSET 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 Fixes: 72b22bbad1e7 ("MIPS: Don't assume 64-bit FP registers for FP regset") Cc: James Hogan Cc: Paul Burton Cc: Alex Smith Cc: Dave Martin 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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c index 0522e717b738e..53c3f4de45d16 100644 --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -497,7 +497,15 @@ static int fpr_set_msa(struct task_struct *target, 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, @@ -505,6 +513,8 @@ static int fpr_set(struct task_struct *target, { int err; + BUG_ON(count % sizeof(elf_fpreg_t)); + /* XXX fcr31 */ if (sizeof(target->thread.fpu.fpr[0]) == sizeof(elf_fpreg_t))