[PATCH 3.16 149/192] sparc: Harden signal return frame checks.

Ben Hutchings
2017-10-09T13:53:43Z

From: "David S. Miller" <davem@davemloft.net>

[ Upstream commit d11c2a0de2824395656cf8ed15811580c9dd38aa ]

All signal frames must be at least 16-byte aligned, because that is
the alignment we explicitly create when we build signal return stack
frames.

All stack pointers must be at least 8-byte aligned.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/sparc/kernel/signal32.c | 46 +++++++++++++++++++++++++++---------------
arch/sparc/kernel/signal_32.c | 41 +++++++++++++++++++++++--------------
arch/sparc/kernel/signal_64.c | 31 ++++++++++++++++++----------
arch/sparc/kernel/sigutil_32.c | 9 ++++++++-
arch/sparc/kernel/sigutil_64.c | 10 +++++++--
5 files changed, 92 insertions(+), 45 deletions(-)

--- a/arch/sparc/kernel/signal32.c
+++ b/arch/sparc/kernel/signal32.c
@@ -138,12 +138,24 @@ int copy_siginfo_from_user32(siginfo_t *
return 0;
}

+/* Checks if the fp is valid. We always build signal frames which are
+ * 16-byte aligned, therefore we can always enforce that the restore
+ * frame has that property as well.
+ */
+static bool invalid_frame_pointer(void __user *fp, int fplen)
+{
+ if ((((unsigned long) fp) & 15) ||
+ ((unsigned long)fp) > 0x100000000ULL - fplen)
+ return true;
+ return false;
+}
+
void do_sigreturn32(struct pt_regs *regs)
{
struct signal_frame32 __user *sf;
compat_uptr_t fpu_save;
compat_uptr_t rwin_save;
- unsigned int psr;
+ unsigned int psr, ufp;
unsigned pc, npc;
sigset_t set;
compat_sigset_t seta;
@@ -158,11 +170,16 @@ void do_sigreturn32(struct pt_regs *regs
sf = (struct signal_frame32 __user *) regs->u_regs[UREG_FP];

/* 1. Make sure we are not getting garbage from the user */
- if (!access_ok(VERIFY_READ, sf, sizeof(*sf)) ||
- (((unsigned long) sf) & 3))
+ if (invalid_frame_pointer(sf, sizeof(*sf)))
+ goto segv;
+
+ if (get_user(ufp, &sf->info.si_regs.u_regs[UREG_FP]))
+ goto segv;
+
+ if (ufp & 0x7)
goto segv;

- if (get_user(pc, &sf->info.si_regs.pc) ||
+ if (__get_user(pc, &sf->info.si_regs.pc) ||
__get_user(npc, &sf->info.si_regs.npc))
goto segv;

@@ -227,7 +244,7 @@ segv:
asmlinkage void do_rt_sigreturn32(struct pt_regs *regs)
{
struct rt_signal_frame32 __user *sf;
- unsigned int psr, pc, npc;
+ unsigned int psr, pc, npc, ufp;
compat_uptr_t fpu_save;
compat_uptr_t rwin_save;
sigset_t set;
@@ -242,11 +259,16 @@ asmlinkage void do_rt_sigreturn32(struct
sf = (struct rt_signal_frame32 __user *) regs->u_regs[UREG_FP];

/* 1. Make sure we are not getting garbage from the user */
- if (!access_ok(VERIFY_READ, sf, sizeof(*sf)) ||
- (((unsigned long) sf) & 3))
+ if (invalid_frame_pointer(sf, sizeof(*sf)))
goto segv;

- if (get_user(pc, &sf->regs.pc) ||
+ if (get_user(ufp, &sf->regs.u_regs[UREG_FP]))
+ goto segv;
+
+ if (ufp & 0x7)
+ goto segv;
+
+ if (__get_user(pc, &sf->regs.pc) ||
__get_user(npc, &sf->regs.npc))
goto segv;

@@ -307,14 +329,6 @@ segv:
force_sig(SIGSEGV, current);
}

-/* Checks if the fp is valid */
-static int invalid_frame_pointer(void __user *fp, int fplen)
-{
- if ((((unsigned long) fp) & 7) || ((unsigned long)fp) > 0x100000000ULL - fplen)
- return 1;
- return 0;
-}
-
static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, unsigned long framesize)
{
unsigned long sp;
--- a/arch/sparc/kernel/signal_32.c
+++ b/arch/sparc/kernel/signal_32.c
@@ -60,10 +60,22 @@ struct rt_signal_frame {
#define SF_ALIGNEDSZ (((sizeof(struct signal_frame) + 7) & (~7)))
#define RT_ALIGNEDSZ (((sizeof(struct rt_signal_frame) + 7) & (~7)))

+/* Checks if the fp is valid. We always build signal frames which are
+ * 16-byte aligned, therefore we can always enforce that the restore
+ * frame has that property as well.
+ */
+static inline bool invalid_frame_pointer(void __user *fp, int fplen)
+{
+ if ((((unsigned long) fp) & 15) || !__access_ok((unsigned long)fp, fplen))
+ return true;
+
+ return false;
+}
+
asmlinkage void do_sigreturn(struct pt_regs *regs)
{
+ unsigned long up_psr, pc, npc, ufp;
struct signal_frame __user *sf;
- unsigned long up_psr, pc, npc;
sigset_t set;
__siginfo_fpu_t __user *fpu_save;
__siginfo_rwin_t __user *rwin_save;
@@ -77,10 +89,13 @@ asmlinkage void do_sigreturn(struct pt_r
sf = (struct signal_frame __user *) regs->u_regs[UREG_FP];

/* 1. Make sure we are not getting garbage from the user */
- if (!access_ok(VERIFY_READ, sf, sizeof(*sf)))
+ if (!invalid_frame_pointer(sf, sizeof(*sf)))
goto segv_and_exit;

- if (((unsigned long) sf) & 3)
+ if (get_user(ufp, &sf->info.si_regs.u_regs[UREG_FP]))
+ goto segv_and_exit;
+
+ if (ufp & 0x7)
goto segv_and_exit;

err = __get_user(pc, &sf->info.si_regs.pc);
@@ -127,7 +142,7 @@ segv_and_exit:
asmlinkage void do_rt_sigreturn(struct pt_regs *regs)
{
struct rt_signal_frame __user *sf;
- unsigned int psr, pc, npc;
+ unsigned int psr, pc, npc, ufp;
__siginfo_fpu_t __user *fpu_save;
__siginfo_rwin_t __user *rwin_save;
sigset_t set;
@@ -135,8 +150,13 @@ asmlinkage void do_rt_sigreturn(struct p

synchronize_user_stack();
sf = (struct rt_signal_frame __user *) regs->u_regs[UREG_FP];
- if (!access_ok(VERIFY_READ, sf, sizeof(*sf)) ||
- (((unsigned long) sf) & 0x03))
+ if (!invalid_frame_pointer(sf, sizeof(*sf)))
+ goto segv;
+
+ if (get_user(ufp, &sf->regs.u_regs[UREG_FP]))
+ goto segv;
+
+ if (ufp & 0x7)
goto segv;

err = __get_user(pc, &sf->regs.pc);
@@ -178,15 +198,6 @@ segv:
force_sig(SIGSEGV, current);
}

-/* Checks if the fp is valid */
-static inline int invalid_frame_pointer(void __user *fp, int fplen)
-{
- if ((((unsigned long) fp) & 7) || !__access_ok((unsigned long)fp, fplen))
- return 1;
-
- return 0;
-}
-
static inline void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, unsigned long framesize)
{
unsigned long sp = regs->u_regs[UREG_FP];
--- a/arch/sparc/kernel/signal_64.c
+++ b/arch/sparc/kernel/signal_64.c
@@ -234,6 +234,17 @@ do_sigsegv:
goto out;
}

+/* Checks if the fp is valid. We always build rt signal frames which
+ * are 16-byte aligned, therefore we can always enforce that the
+ * restore frame has that property as well.
+ */
+static bool invalid_frame_pointer(void __user *fp)
+{
+ if (((unsigned long) fp) & 15)
+ return true;
+ return false;
+}
+
struct rt_signal_frame {
struct sparc_stackf ss;
siginfo_t info;
@@ -246,8 +257,8 @@ struct rt_signal_frame {

void do_rt_sigreturn(struct pt_regs *regs)
{
+ unsigned long tpc, tnpc, tstate, ufp;
struct rt_signal_frame __user *sf;
- unsigned long tpc, tnpc, tstate;
__siginfo_fpu_t __user *fpu_save;
__siginfo_rwin_t __user *rwin_save;
sigset_t set;
@@ -261,10 +272,16 @@ void do_rt_sigreturn(struct pt_regs *reg
(regs->u_regs [UREG_FP] + STACK_BIAS);

/* 1. Make sure we are not getting garbage from the user */
- if (((unsigned long) sf) & 3)
+ if (invalid_frame_pointer(sf))
+ goto segv;
+
+ if (get_user(ufp, &sf->regs.u_regs[UREG_FP]))
goto segv;

- err = get_user(tpc, &sf->regs.tpc);
+ if ((ufp + STACK_BIAS) & 0x7)
+ goto segv;
+
+ err = __get_user(tpc, &sf->regs.tpc);
err |= __get_user(tnpc, &sf->regs.tnpc);
if (test_thread_flag(TIF_32BIT)) {
tpc &= 0xffffffff;
@@ -308,14 +325,6 @@ segv:
force_sig(SIGSEGV, current);
}

-/* Checks if the fp is valid */
-static int invalid_frame_pointer(void __user *fp)
-{
- if (((unsigned long) fp) & 15)
- return 1;
- return 0;
-}
-
static inline void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, unsigned long framesize)
{
unsigned long sp = regs->u_regs[UREG_FP] + STACK_BIAS;
--- a/arch/sparc/kernel/sigutil_32.c
+++ b/arch/sparc/kernel/sigutil_32.c
@@ -48,6 +48,10 @@ int save_fpu_state(struct pt_regs *regs,
int restore_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
{
int err;
+
+ if (((unsigned long) fpu) & 3)
+ return -EFAULT;
+
#ifdef CONFIG_SMP
if (test_tsk_thread_flag(current, TIF_USEDFPU))
regs->psr &= ~PSR_EF;
@@ -97,7 +101,10 @@ int restore_rwin_state(__siginfo_rwin_t
struct thread_info *t = current_thread_info();
int i, wsaved, err;

- __get_user(wsaved, &rp->wsaved);
+ if (((unsigned long) rp) & 3)
+ return -EFAULT;
+
+ get_user(wsaved, &rp->wsaved);
if (wsaved > NSWINS)
return -EFAULT;

--- a/arch/sparc/kernel/sigutil_64.c
+++ b/arch/sparc/kernel/sigutil_64.c
@@ -37,7 +37,10 @@ int restore_fpu_state(struct pt_regs *re
unsigned long fprs;
int err;

- err = __get_user(fprs, &fpu->si_fprs);
+ if (((unsigned long) fpu) & 7)
+ return -EFAULT;
+
+ err = get_user(fprs, &fpu->si_fprs);
fprs_write(0);
regs->tstate &= ~TSTATE_PEF;
if (fprs & FPRS_DL)
@@ -72,7 +75,10 @@ int restore_rwin_state(__siginfo_rwin_t
struct thread_info *t = current_thread_info();
int i, wsaved, err;

- __get_user(wsaved, &rp->wsaved);
+ if (((unsigned long) rp) & 7)
+ return -EFAULT;
+
+ get_user(wsaved, &rp->wsaved);
if (wsaved > NSWINS)
return -EFAULT;