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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Dave Martin <Dave.Martin@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 181/293] arm64: ptrace: Fix incorrect
 get_user() use in compat_vfp_set()
Thread-Topic: [PATCH AUTOSEL for 4.9 181/293] arm64: ptrace: Fix incorrect
 get_user() use in compat_vfp_set()
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Date:   Mon, 9 Apr 2018 00:25:16 +0000
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From: Dave Martin <Dave.Martin@arm.com>

[ Upstream commit 5fbd5fc49fc39ac8433da62d16682a1d0217ea4f ]

Now that compat_vfp_get() uses the regset API to copy the FPSCR
value out to userspace, compat_vfp_set() looks inconsistent.  In
particular, compat_vfp_set() will fail if called with kbuf !=3D NULL
&& ubuf =3D=3D NULL (which is valid usage according to the regset API).

This patch fixes compat_vfp_set() to use user_regset_copyin(),
similarly to compat_vfp_get().

This also squashes a sparse warning triggered by the cast that
drops __user when calling get_user().

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/arm64/kernel/ptrace.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index cca95e75aaeb..df1addf104f5 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -926,18 +926,20 @@ static int compat_vfp_set(struct task_struct *target,
 {
 	struct user_fpsimd_state *uregs;
 	compat_ulong_t fpscr;
-	int ret;
+	int ret, vregs_end_pos;
=20
 	if (pos + count > VFP_STATE_SIZE)
 		return -EIO;
=20
 	uregs =3D &target->thread.fpsimd_state.user_fpsimd;
=20
+	vregs_end_pos =3D VFP_STATE_SIZE - sizeof(compat_ulong_t);
 	ret =3D user_regset_copyin(&pos, &count, &kbuf, &ubuf, uregs, 0,
-				 VFP_STATE_SIZE - sizeof(compat_ulong_t));
+				 vregs_end_pos);
=20
 	if (count && !ret) {
-		ret =3D get_user(fpscr, (compat_ulong_t *)ubuf);
+		ret =3D user_regset_copyin(&pos, &count, &kbuf, &ubuf, &fpscr,
+					 vregs_end_pos, VFP_STATE_SIZE);
 		if (!ret) {
 			uregs->fpsr =3D fpscr & VFP_FPSCR_STAT_MASK;
 			uregs->fpcr =3D fpscr & VFP_FPSCR_CTRL_MASK;
--=20
2.15.1