From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave.Martin@arm.com (Dave Martin) Date: Thu, 29 Jun 2017 15:25:47 +0100 Subject: [PATCH 1/3] arm64: ptrace: Avoid setting compat FP[SC]R to garbage if get_user fails In-Reply-To: <1498746379-27340-1-git-send-email-Dave.Martin@arm.com> References: <1498746379-27340-1-git-send-email-Dave.Martin@arm.com> Message-ID: <1498746379-27340-2-git-send-email-Dave.Martin@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org If get_user() fails when reading the new FPSCR value from userspace in compat_vfp_get(), then garbage* will be written to the task's FPSR and FPCR registers. This patch prevents this by checking the return from get_user() first. [*] Actually, zero, due to the behaviour of get_user() on error, but that's still not what userspace expects. Fixes: 478fcb2cdb23 ("arm64: Debugging support") Signed-off-by: Dave Martin --- arch/arm64/kernel/ptrace.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 35846f1..4c068dc 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -947,8 +947,10 @@ static int compat_vfp_set(struct task_struct *target, if (count && !ret) { ret = get_user(fpscr, (compat_ulong_t *)ubuf); - uregs->fpsr = fpscr & VFP_FPSCR_STAT_MASK; - uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK; + if (!ret) { + uregs->fpsr = fpscr & VFP_FPSCR_STAT_MASK; + uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK; + } } fpsimd_flush_task_state(target); -- 2.1.4