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s390/signal: set correct address space control

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If user space is running in primary mode it can switch to secondary
or access register mode, this is used e.g. in the clock_gettime code
of the vdso. If a signal is delivered to the user space process while
it has been running in access register mode the signal handler is
executed in access register mode as well which will result in a crash
most of the time.

Set the address space control bits in the PSW to the default for the
execution of the signal handler and make sure that the previous
address space control is restored on signal return. Take care
that user space can not switch to the kernel address space by
modifying the registers in the signal frame.

Cc: stable@vger.kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2012-11-07 10:44:08 +01:00
parent 77b67063bb
commit fa968ee215
4 changed files with 27 additions and 7 deletions
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14
arch/s390/kernel/compat_signal.c
View file

@ -309,6 +309,10 @@ static int restore_sigregs32(struct pt_regs *regs,_sigregs32 __user *sregs)
regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
(__u64)(regs32.psw.mask & PSW32_MASK_USER) << 32 |
(__u64)(regs32.psw.addr & PSW32_ADDR_AMODE);
/* Check for invalid user address space control. */
if ((regs->psw.mask & PSW_MASK_ASC) >= (psw_kernel_bits & PSW_MASK_ASC))
regs->psw.mask = (psw_user_bits & PSW_MASK_ASC) |
(regs->psw.mask & ~PSW_MASK_ASC);
regs->psw.addr = (__u64)(regs32.psw.addr & PSW32_ADDR_INSN);
for (i = 0; i < NUM_GPRS; i++)
regs->gprs[i] = (__u64) regs32.gprs[i];
@ -481,7 +485,10 @@ static int setup_frame32(int sig, struct k_sigaction *ka,
/* Set up registers for signal handler */
regs->gprs[15] = (__force __u64) frame;
regs->psw.mask |= PSW_MASK_BA; /* force amode 31 */
/* Force 31 bit amode and default user address space control. */
regs->psw.mask = PSW_MASK_BA |
(psw_user_bits & PSW_MASK_ASC) |
(regs->psw.mask & ~PSW_MASK_ASC);
regs->psw.addr = (__force __u64) ka->sa.sa_handler;
regs->gprs[2] = map_signal(sig);
@ -549,7 +556,10 @@ static int setup_rt_frame32(int sig, struct k_sigaction *ka, siginfo_t *info,
/* Set up registers for signal handler */
regs->gprs[15] = (__force __u64) frame;
regs->psw.mask |= PSW_MASK_BA; /* force amode 31 */
/* Force 31 bit amode and default user address space control. */
regs->psw.mask = PSW_MASK_BA |
(psw_user_bits & PSW_MASK_ASC) |
(regs->psw.mask & ~PSW_MASK_ASC);
regs->psw.addr = (__u64) ka->sa.sa_handler;
regs->gprs[2] = map_signal(sig);