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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-15 16:08:34 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-24 17:17:11 +0200
commit4725c86055f5bbdcdfe47199c0715881893a2c79 (patch)
treee201bd8d8a11e58117e9ecf360f3fab43c6267e9 /arch/s390/kernel/signal.c
parent01a7cfa24afd8e18ce691d3c2f1e1f093cf3a900 (diff)
s390: fix save and restore of the floating-point-control register
The FPC_VALID_MASK has been used to check the validity of the value to be loaded into the floating-point-control register. With the introduction of the floating-point extension facility and the decimal-floating-point additional bits have been defined which need to be checked in a non straight forward way. So far these bits have been ignored which can cause an incorrect results for decimal- floating-point operations, e.g. an incorrect rounding mode to be set after signal return. The static check with the FPC_VALID_MASK is replaced with a trial load of the floating-point-control value, see test_fp_ctl. In addition an information leak with the padding word between the floating-point-control word and the floating-point registers in the s390_fp_regs is fixed. Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com> Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/signal.c')
-rw-r--r--arch/s390/kernel/signal.c21
1 files changed, 13 insertions, 8 deletions
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 5c0ce019a8a..4c28c39e371 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -62,14 +62,15 @@ static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
user_sregs.regs.psw.addr = regs->psw.addr;
memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
memcpy(&user_sregs.regs.acrs, current->thread.acrs,
- sizeof(sregs->regs.acrs));
+ sizeof(user_sregs.regs.acrs));
/*
* We have to store the fp registers to current->thread.fp_regs
* to merge them with the emulated registers.
*/
- save_fp_regs(&current->thread.fp_regs);
+ save_fp_ctl(&current->thread.fp_regs.fpc);
+ save_fp_regs(current->thread.fp_regs.fprs);
memcpy(&user_sregs.fpregs, &current->thread.fp_regs,
- sizeof(s390_fp_regs));
+ sizeof(user_sregs.fpregs));
if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs)))
return -EFAULT;
return 0;
@@ -82,8 +83,13 @@ static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
/* Alwys make any pending restarted system call return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
- if (__copy_from_user(&user_sregs, sregs, sizeof(_sigregs)))
+ if (__copy_from_user(&user_sregs, sregs, sizeof(user_sregs)))
return -EFAULT;
+
+ /* Loading the floating-point-control word can fail. Do that first. */
+ if (restore_fp_ctl(&user_sregs.fpregs.fpc))
+ return -EINVAL;
+
/* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */
regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
(user_sregs.regs.psw.mask & PSW_MASK_USER);
@@ -97,14 +103,13 @@ static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
regs->psw.addr = user_sregs.regs.psw.addr;
memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
- sizeof(sregs->regs.acrs));
+ sizeof(current->thread.acrs));
restore_access_regs(current->thread.acrs);
memcpy(&current->thread.fp_regs, &user_sregs.fpregs,
- sizeof(s390_fp_regs));
- current->thread.fp_regs.fpc &= FPC_VALID_MASK;
+ sizeof(current->thread.fp_regs));
- restore_fp_regs(&current->thread.fp_regs);
+ restore_fp_regs(current->thread.fp_regs.fprs);
clear_thread_flag(TIF_SYSCALL); /* No longer in a system call */
return 0;
}