sparc64: Fix race in signal instruction flushing.

If another cpu does a very wide munmap() on the signal frame area,
it can tear down the page table hierarchy from underneath us.

Borrow an idea from the 64-bit fault path's get_user_insn(), and
disable cross call interrupts during the page table traversal
to lock them in place while we operate.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2010-09-20 23:24:52 -07:00
parent b343ae51c1
commit 05c5e7698b

View File

@ -453,6 +453,64 @@ static int save_fpu_state32(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
return err;
}
/* The I-cache flush instruction only works in the primary ASI, which
* right now is the nucleus, aka. kernel space.
*
* Therefore we have to kick the instructions out using the kernel
* side linear mapping of the physical address backing the user
* instructions.
*/
static void flush_signal_insns(unsigned long address)
{
unsigned long pstate, paddr;
pte_t *ptep, pte;
pgd_t *pgdp;
pud_t *pudp;
pmd_t *pmdp;
/* Commit all stores of the instructions we are about to flush. */
wmb();
/* Disable cross-call reception. In this way even a very wide
* munmap() on another cpu can't tear down the page table
* hierarchy from underneath us, since that can't complete
* until the IPI tlb flush returns.
*/
__asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));
__asm__ __volatile__("wrpr %0, %1, %%pstate"
: : "r" (pstate), "i" (PSTATE_IE));
pgdp = pgd_offset(current->mm, address);
if (pgd_none(*pgdp))
goto out_irqs_on;
pudp = pud_offset(pgdp, address);
if (pud_none(*pudp))
goto out_irqs_on;
pmdp = pmd_offset(pudp, address);
if (pmd_none(*pmdp))
goto out_irqs_on;
ptep = pte_offset_map(pmdp, address);
pte = *ptep;
if (!pte_present(pte))
goto out_unmap;
paddr = (unsigned long) page_address(pte_page(pte));
__asm__ __volatile__("flush %0 + %1"
: /* no outputs */
: "r" (paddr),
"r" (address & (PAGE_SIZE - 1))
: "memory");
out_unmap:
pte_unmap(ptep);
out_irqs_on:
__asm__ __volatile__("wrpr %0, 0x0, %%pstate" : : "r" (pstate));
}
static void setup_frame32(struct k_sigaction *ka, struct pt_regs *regs,
int signo, sigset_t *oldset)
{
@ -547,13 +605,7 @@ static void setup_frame32(struct k_sigaction *ka, struct pt_regs *regs,
if (ka->ka_restorer) {
regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
} else {
/* Flush instruction space. */
unsigned long address = ((unsigned long)&(sf->insns[0]));
pgd_t *pgdp = pgd_offset(current->mm, address);
pud_t *pudp = pud_offset(pgdp, address);
pmd_t *pmdp = pmd_offset(pudp, address);
pte_t *ptep;
pte_t pte;
regs->u_regs[UREG_I7] = (unsigned long) (&(sf->insns[0]) - 2);
@ -562,22 +614,7 @@ static void setup_frame32(struct k_sigaction *ka, struct pt_regs *regs,
if (err)
goto sigsegv;
preempt_disable();
ptep = pte_offset_map(pmdp, address);
pte = *ptep;
if (pte_present(pte)) {
unsigned long page = (unsigned long)
page_address(pte_page(pte));
wmb();
__asm__ __volatile__("flush %0 + %1"
: /* no outputs */
: "r" (page),
"r" (address & (PAGE_SIZE - 1))
: "memory");
}
pte_unmap(ptep);
preempt_enable();
flush_signal_insns(address);
}
return;
@ -687,12 +724,7 @@ static void setup_rt_frame32(struct k_sigaction *ka, struct pt_regs *regs,
if (ka->ka_restorer)
regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
else {
/* Flush instruction space. */
unsigned long address = ((unsigned long)&(sf->insns[0]));
pgd_t *pgdp = pgd_offset(current->mm, address);
pud_t *pudp = pud_offset(pgdp, address);
pmd_t *pmdp = pmd_offset(pudp, address);
pte_t *ptep;
regs->u_regs[UREG_I7] = (unsigned long) (&(sf->insns[0]) - 2);
@ -704,21 +736,7 @@ static void setup_rt_frame32(struct k_sigaction *ka, struct pt_regs *regs,
if (err)
goto sigsegv;
preempt_disable();
ptep = pte_offset_map(pmdp, address);
if (pte_present(*ptep)) {
unsigned long page = (unsigned long)
page_address(pte_page(*ptep));
wmb();
__asm__ __volatile__("flush %0 + %1"
: /* no outputs */
: "r" (page),
"r" (address & (PAGE_SIZE - 1))
: "memory");
}
pte_unmap(ptep);
preempt_enable();
flush_signal_insns(address);
}
return;