mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 10:49:33 +00:00
![Cliff Wickman](/assets/img/avatar_default.png)
A panic can be caused by simply cat'ing /proc/<pid>/smaps while an application has a VM_PFNMAP range. It happened in-house when a benchmarker was trying to decipher the memory layout of his program. /proc/<pid>/smaps and similar walks through a user page table should not be looking at VM_PFNMAP areas. Certain tests in walk_page_range() (specifically split_huge_page_pmd()) assume that all the mapped PFN's are backed with page structures. And this is not usually true for VM_PFNMAP areas. This can result in panics on kernel page faults when attempting to address those page structures. There are a half dozen callers of walk_page_range() that walk through a task's entire page table (as N. Horiguchi pointed out). So rather than change all of them, this patch changes just walk_page_range() to ignore VM_PFNMAP areas. The logic of hugetlb_vma() is moved back into walk_page_range(), as we want to test any vma in the range. VM_PFNMAP areas are used by: - graphics memory manager gpu/drm/drm_gem.c - global reference unit sgi-gru/grufile.c - sgi special memory char/mspec.c - and probably several out-of-tree modules [akpm@linux-foundation.org: remove now-unused hugetlb_vma() stub] Signed-off-by: Cliff Wickman <cpw@sgi.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: David Sterba <dsterba@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
248 lines
5.9 KiB
C
248 lines
5.9 KiB
C
#include <linux/mm.h>
|
|
#include <linux/highmem.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/hugetlb.h>
|
|
|
|
static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
pte_t *pte;
|
|
int err = 0;
|
|
|
|
pte = pte_offset_map(pmd, addr);
|
|
for (;;) {
|
|
err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
|
|
if (err)
|
|
break;
|
|
addr += PAGE_SIZE;
|
|
if (addr == end)
|
|
break;
|
|
pte++;
|
|
}
|
|
|
|
pte_unmap(pte);
|
|
return err;
|
|
}
|
|
|
|
static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
pmd_t *pmd;
|
|
unsigned long next;
|
|
int err = 0;
|
|
|
|
pmd = pmd_offset(pud, addr);
|
|
do {
|
|
again:
|
|
next = pmd_addr_end(addr, end);
|
|
if (pmd_none(*pmd)) {
|
|
if (walk->pte_hole)
|
|
err = walk->pte_hole(addr, next, walk);
|
|
if (err)
|
|
break;
|
|
continue;
|
|
}
|
|
/*
|
|
* This implies that each ->pmd_entry() handler
|
|
* needs to know about pmd_trans_huge() pmds
|
|
*/
|
|
if (walk->pmd_entry)
|
|
err = walk->pmd_entry(pmd, addr, next, walk);
|
|
if (err)
|
|
break;
|
|
|
|
/*
|
|
* Check this here so we only break down trans_huge
|
|
* pages when we _need_ to
|
|
*/
|
|
if (!walk->pte_entry)
|
|
continue;
|
|
|
|
split_huge_page_pmd_mm(walk->mm, addr, pmd);
|
|
if (pmd_none_or_trans_huge_or_clear_bad(pmd))
|
|
goto again;
|
|
err = walk_pte_range(pmd, addr, next, walk);
|
|
if (err)
|
|
break;
|
|
} while (pmd++, addr = next, addr != end);
|
|
|
|
return err;
|
|
}
|
|
|
|
static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
pud_t *pud;
|
|
unsigned long next;
|
|
int err = 0;
|
|
|
|
pud = pud_offset(pgd, addr);
|
|
do {
|
|
next = pud_addr_end(addr, end);
|
|
if (pud_none_or_clear_bad(pud)) {
|
|
if (walk->pte_hole)
|
|
err = walk->pte_hole(addr, next, walk);
|
|
if (err)
|
|
break;
|
|
continue;
|
|
}
|
|
if (walk->pud_entry)
|
|
err = walk->pud_entry(pud, addr, next, walk);
|
|
if (!err && (walk->pmd_entry || walk->pte_entry))
|
|
err = walk_pmd_range(pud, addr, next, walk);
|
|
if (err)
|
|
break;
|
|
} while (pud++, addr = next, addr != end);
|
|
|
|
return err;
|
|
}
|
|
|
|
#ifdef CONFIG_HUGETLB_PAGE
|
|
static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
|
|
unsigned long end)
|
|
{
|
|
unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
|
|
return boundary < end ? boundary : end;
|
|
}
|
|
|
|
static int walk_hugetlb_range(struct vm_area_struct *vma,
|
|
unsigned long addr, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
struct hstate *h = hstate_vma(vma);
|
|
unsigned long next;
|
|
unsigned long hmask = huge_page_mask(h);
|
|
pte_t *pte;
|
|
int err = 0;
|
|
|
|
do {
|
|
next = hugetlb_entry_end(h, addr, end);
|
|
pte = huge_pte_offset(walk->mm, addr & hmask);
|
|
if (pte && walk->hugetlb_entry)
|
|
err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
|
|
if (err)
|
|
return err;
|
|
} while (addr = next, addr != end);
|
|
|
|
return 0;
|
|
}
|
|
|
|
#else /* CONFIG_HUGETLB_PAGE */
|
|
static int walk_hugetlb_range(struct vm_area_struct *vma,
|
|
unsigned long addr, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
#endif /* CONFIG_HUGETLB_PAGE */
|
|
|
|
|
|
|
|
/**
|
|
* walk_page_range - walk a memory map's page tables with a callback
|
|
* @addr: starting address
|
|
* @end: ending address
|
|
* @walk: set of callbacks to invoke for each level of the tree
|
|
*
|
|
* Recursively walk the page table for the memory area in a VMA,
|
|
* calling supplied callbacks. Callbacks are called in-order (first
|
|
* PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
|
|
* etc.). If lower-level callbacks are omitted, walking depth is reduced.
|
|
*
|
|
* Each callback receives an entry pointer and the start and end of the
|
|
* associated range, and a copy of the original mm_walk for access to
|
|
* the ->private or ->mm fields.
|
|
*
|
|
* Usually no locks are taken, but splitting transparent huge page may
|
|
* take page table lock. And the bottom level iterator will map PTE
|
|
* directories from highmem if necessary.
|
|
*
|
|
* If any callback returns a non-zero value, the walk is aborted and
|
|
* the return value is propagated back to the caller. Otherwise 0 is returned.
|
|
*
|
|
* walk->mm->mmap_sem must be held for at least read if walk->hugetlb_entry
|
|
* is !NULL.
|
|
*/
|
|
int walk_page_range(unsigned long addr, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
pgd_t *pgd;
|
|
unsigned long next;
|
|
int err = 0;
|
|
|
|
if (addr >= end)
|
|
return err;
|
|
|
|
if (!walk->mm)
|
|
return -EINVAL;
|
|
|
|
VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
|
|
|
|
pgd = pgd_offset(walk->mm, addr);
|
|
do {
|
|
struct vm_area_struct *vma = NULL;
|
|
|
|
next = pgd_addr_end(addr, end);
|
|
|
|
/*
|
|
* This function was not intended to be vma based.
|
|
* But there are vma special cases to be handled:
|
|
* - hugetlb vma's
|
|
* - VM_PFNMAP vma's
|
|
*/
|
|
vma = find_vma(walk->mm, addr);
|
|
if (vma) {
|
|
/*
|
|
* There are no page structures backing a VM_PFNMAP
|
|
* range, so do not allow split_huge_page_pmd().
|
|
*/
|
|
if ((vma->vm_start <= addr) &&
|
|
(vma->vm_flags & VM_PFNMAP)) {
|
|
next = vma->vm_end;
|
|
pgd = pgd_offset(walk->mm, next);
|
|
continue;
|
|
}
|
|
/*
|
|
* Handle hugetlb vma individually because pagetable
|
|
* walk for the hugetlb page is dependent on the
|
|
* architecture and we can't handled it in the same
|
|
* manner as non-huge pages.
|
|
*/
|
|
if (walk->hugetlb_entry && (vma->vm_start <= addr) &&
|
|
is_vm_hugetlb_page(vma)) {
|
|
if (vma->vm_end < next)
|
|
next = vma->vm_end;
|
|
/*
|
|
* Hugepage is very tightly coupled with vma,
|
|
* so walk through hugetlb entries within a
|
|
* given vma.
|
|
*/
|
|
err = walk_hugetlb_range(vma, addr, next, walk);
|
|
if (err)
|
|
break;
|
|
pgd = pgd_offset(walk->mm, next);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (pgd_none_or_clear_bad(pgd)) {
|
|
if (walk->pte_hole)
|
|
err = walk->pte_hole(addr, next, walk);
|
|
if (err)
|
|
break;
|
|
pgd++;
|
|
continue;
|
|
}
|
|
if (walk->pgd_entry)
|
|
err = walk->pgd_entry(pgd, addr, next, walk);
|
|
if (!err &&
|
|
(walk->pud_entry || walk->pmd_entry || walk->pte_entry))
|
|
err = walk_pud_range(pgd, addr, next, walk);
|
|
if (err)
|
|
break;
|
|
pgd++;
|
|
} while (addr = next, addr != end);
|
|
|
|
return err;
|
|
}
|