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[PATCH] lock PTE before updating it in 440/BookE page fault handler

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Fix 44x and BookE page fault handler to correctly lock PTE before
trying to pte_update() it, otherwise this PTE might be swapped out
after pte_present() check but before pte_uptdate() call, resulting in
corrupted PTE. This can happen with enabled preemption and low memory
condition.

Signed-off-by: Eugene Surovegin <ebs@ebshome.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Eugene Surovegin
2006-03-28 10:13:12 -08:00
committed by Paul Mackerras
parent bac30d1a78
commit bab70a4af7
5 changed files with 42 additions and 29 deletions
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28
arch/ppc/mm/fault.c
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@@ -202,6 +202,7 @@ good_area:
/* an exec - 4xx/Book-E allows for per-page execute permission */
} else if (TRAP(regs) == 0x400) {
pte_t *ptep;
pmd_t *pmdp;
#if 0
/* It would be nice to actually enforce the VM execute
@@ -215,21 +216,24 @@ good_area:
/* Since 4xx/Book-E supports per-page execute permission,
* we lazily flush dcache to icache. */
ptep = NULL;
if (get_pteptr(mm, address, &ptep) && pte_present(*ptep)) {
struct page *page = pte_page(*ptep);
if (get_pteptr(mm, address, &ptep, &pmdp)) {
spinlock_t *ptl = pte_lockptr(mm, pmdp);
spin_lock(ptl);
if (pte_present(*ptep)) {
struct page *page = pte_page(*ptep);
if (! test_bit(PG_arch_1, &page->flags)) {
flush_dcache_icache_page(page);
set_bit(PG_arch_1, &page->flags);
if (!test_bit(PG_arch_1, &page->flags)) {
flush_dcache_icache_page(page);
set_bit(PG_arch_1, &page->flags);
}
pte_update(ptep, 0, _PAGE_HWEXEC);
_tlbie(address);
pte_unmap_unlock(ptep, ptl);
up_read(&mm->mmap_sem);
return 0;
}
pte_update(ptep, 0, _PAGE_HWEXEC);
_tlbie(address);
pte_unmap(ptep);
up_read(&mm->mmap_sem);
return 0;
pte_unmap_unlock(ptep, ptl);
}
if (ptep != NULL)
pte_unmap(ptep);
#endif
/* a read */
} else {