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[S390] Improve address space check.

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A data access in access-register mode always is a user mode access,
the code to inspect the access-registers can be removed. The second
change is to use a different test to check for no-execute fault.
The third change is to pass the translation exception identification
as parameter, in theory the trans_exc_code in the lowcore could have
been overwritten by the time the call to check_space from do_no_context
is done.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2009-12-07 12:51:42 +01:00 committed by Martin Schwidefsky
parent d40f7b75a2
commit 61365e132e
1 changed files with 45 additions and 54 deletions
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99
arch/s390/mm/fault.c
View file

@ -100,39 +100,28 @@ void bust_spinlocks(int yes)
/*
* Returns the address space associated with the fault.
* Returns 0 for kernel space, 1 for user space and
* 2 for code execution in user space with noexec=on.
* Returns 0 for kernel space and 1 for user space.
*/
static inline int check_space(struct task_struct *tsk)
static inline int user_space_fault(unsigned long trans_exc_code)
{
/*
* The lowest two bits of S390_lowcore.trans_exc_code
* indicate which paging table was used.
* The lowest two bits of the translation exception
* identification indicate which paging table was used.
*/
int desc = S390_lowcore.trans_exc_code & 3;
if (desc == 3) /* Home Segment Table Descriptor */
return switch_amode == 0;
if (desc == 2) /* Secondary Segment Table Descriptor */
return tsk->thread.mm_segment.ar4;
#ifdef CONFIG_S390_SWITCH_AMODE
if (unlikely(desc == 1)) { /* STD determined via access register */
/* %a0 always indicates primary space. */
if (S390_lowcore.exc_access_id != 0) {
save_access_regs(tsk->thread.acrs);
/*
* An alet of 0 indicates primary space.
* An alet of 1 indicates secondary space.
* Any other alet values generate an
* alen-translation exception.
*/
if (tsk->thread.acrs[S390_lowcore.exc_access_id])
return tsk->thread.mm_segment.ar4;
}
}
#endif
/* Primary Segment Table Descriptor */
return switch_amode << s390_noexec;
trans_exc_code &= 3;
if (trans_exc_code == 2)
/* Access via secondary space, set_fs setting decides */
return current->thread.mm_segment.ar4;
if (!switch_amode)
/* User space if the access has been done via home space. */
return trans_exc_code == 3;
/*
* If the user space is not the home space the kernel runs in home
* space. Access via secondary space has already been covered,
* access via primary space or access register is from user space
* and access via home space is from the kernel.
*/
return trans_exc_code != 3;
}
/*
@ -162,9 +151,10 @@ static void do_sigsegv(struct pt_regs *regs, unsigned long error_code,
}
static void do_no_context(struct pt_regs *regs, unsigned long error_code,
unsigned long address)
unsigned long trans_exc_code)
{
const struct exception_table_entry *fixup;
unsigned long address;
/* Are we prepared to handle this kernel fault? */
fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK);
@ -177,7 +167,8 @@ static void do_no_context(struct pt_regs *regs, unsigned long error_code,
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
*/
if (check_space(current) == 0)
address = trans_exc_code & __FAIL_ADDR_MASK;
if (user_space_fault(trans_exc_code) == 0)
printk(KERN_ALERT "Unable to handle kernel pointer dereference"
" at virtual kernel address %p\n", (void *)address);
else
@ -188,7 +179,8 @@ static void do_no_context(struct pt_regs *regs, unsigned long error_code,
do_exit(SIGKILL);
}
static void do_low_address(struct pt_regs *regs, unsigned long error_code)
static void do_low_address(struct pt_regs *regs, unsigned long error_code,
unsigned long trans_exc_code)
{
/* Low-address protection hit in kernel mode means
NULL pointer write access in kernel mode. */
@ -198,11 +190,11 @@ static void do_low_address(struct pt_regs *regs, unsigned long error_code)
do_exit(SIGKILL);
}
do_no_context(regs, error_code, 0);
do_no_context(regs, error_code, trans_exc_code);
}
static void do_sigbus(struct pt_regs *regs, unsigned long error_code,
unsigned long address)
unsigned long trans_exc_code)
{
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
@ -212,13 +204,13 @@ static void do_sigbus(struct pt_regs *regs, unsigned long error_code,
* Send a sigbus, regardless of whether we were in kernel
* or user mode.
*/
tsk->thread.prot_addr = address;
tsk->thread.prot_addr = trans_exc_code & __FAIL_ADDR_MASK;
tsk->thread.trap_no = error_code;
force_sig(SIGBUS, tsk);
/* Kernel mode? Handle exceptions or die */
if (!(regs->psw.mask & PSW_MASK_PSTATE))
do_no_context(regs, error_code, address);
do_no_context(regs, error_code, trans_exc_code);
}
#ifdef CONFIG_S390_EXEC_PROTECT
@ -272,13 +264,13 @@ static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
* 3b Region third trans. -> Not present (nullification)
*/
static inline void
do_exception(struct pt_regs *regs, unsigned long error_code, int write)
do_exception(struct pt_regs *regs, unsigned long error_code, int write,
unsigned long trans_exc_code)
{
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct *vma;
unsigned long address;
int space;
int si_code;
int fault;
@ -288,18 +280,15 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int write)
tsk = current;
mm = tsk->mm;
/* get the failing address and the affected space */
address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
space = check_space(tsk);
/*
* Verify that the fault happened in user space, that
* we are not in an interrupt and that there is a
* user context.
*/
if (unlikely(space == 0 || in_atomic() || !mm))
if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm))
goto no_context;
address = trans_exc_code & __FAIL_ADDR_MASK;
/*
* When we get here, the fault happened in the current
* task's user address space, so we can switch on the
@ -315,7 +304,8 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int write)
goto bad_area;
#ifdef CONFIG_S390_EXEC_PROTECT
if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC)))
if (unlikely((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_SECONDARY &&
(trans_exc_code & 3) == 0 && !(vma->vm_flags & VM_EXEC)))
if (!signal_return(mm, regs, address, error_code))
/*
* signal_return() has done an up_read(&mm->mmap_sem)
@ -397,12 +387,14 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int write)
}
no_context:
do_no_context(regs, error_code, address);
do_no_context(regs, error_code, trans_exc_code);
}
void __kprobes do_protection_exception(struct pt_regs *regs,
long error_code)
{
unsigned long trans_exc_code = S390_lowcore.trans_exc_code;
/* Protection exception is supressing, decrement psw address. */
regs->psw.addr -= (error_code >> 16);
/*
@ -410,31 +402,30 @@ void __kprobes do_protection_exception(struct pt_regs *regs,
* as a special case because the translation exception code
* field is not guaranteed to contain valid data in this case.
*/
if (unlikely(!(S390_lowcore.trans_exc_code & 4))) {
do_low_address(regs, error_code);
if (unlikely(!(trans_exc_code & 4))) {
do_low_address(regs, error_code, trans_exc_code);
return;
}
do_exception(regs, 4, 1);
do_exception(regs, 4, 1, trans_exc_code);
}
void __kprobes do_dat_exception(struct pt_regs *regs, long error_code)
{
do_exception(regs, error_code & 0xff, 0);
do_exception(regs, error_code & 0xff, 0, S390_lowcore.trans_exc_code);
}
#ifdef CONFIG_64BIT
void __kprobes do_asce_exception(struct pt_regs *regs, unsigned long error_code)
{
unsigned long trans_exc_code = S390_lowcore.trans_exc_code;
struct mm_struct *mm;
struct vm_area_struct *vma;
unsigned long address;
int space;
mm = current->mm;
address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
space = check_space(current);
address = trans_exc_code & __FAIL_ADDR_MASK;
if (unlikely(space == 0 || in_atomic() || !mm))
if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm))
goto no_context;
local_irq_enable();
@ -457,7 +448,7 @@ void __kprobes do_asce_exception(struct pt_regs *regs, unsigned long error_code)
}
no_context:
do_no_context(regs, error_code, address);
do_no_context(regs, error_code, trans_exc_code);
}
#endif