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    Subject[098/127] sparc64: Fix race in signal instruction flushing.
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

    ------------------


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

    [ Upstream commit 05c5e7698bdc54b3079a3517d86077f49ebcc788 ]

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    arch/sparc/kernel/signal32.c | 102 +++++++++++++++++++++++++------------------
    1 file changed, 60 insertions(+), 42 deletions(-)

    --- a/arch/sparc/kernel/signal32.c
    +++ b/arch/sparc/kernel/signal32.c
    @@ -453,6 +453,64 @@ static int save_fpu_state32(struct pt_re
    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_sigac
    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_sigac
    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_si
    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_si
    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;




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