# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1214337767 -3600
# Node ID 043dc7488c1105670a78cd45efa459fc4defa52d
# Parent 5201a184f5131c76f8263aa70c031c00dd094067
privcmd: avoid deadlock due to copy_(to|from)_user with mmap_sem write lock
held.
Accessing user memory with the write lock held is illegal, if the pages are
non-present then we will deadlock against the lock in do_page_fault. Avoid this
for IOCTL_PRIVCMD_MMAP and MMAPBATCH by copying the entire input data structure
into the kernel before taking the lock.
Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
drivers/xen/privcmd/privcmd.c | 162 ++++++++++++++++++++++++++++++------------
1 files changed, 117 insertions(+), 45 deletions(-)
diff -r 5201a184f513 -r 043dc7488c11 drivers/xen/privcmd/privcmd.c
--- a/drivers/xen/privcmd/privcmd.c Fri Jun 20 17:43:16 2008 +0100
+++ b/drivers/xen/privcmd/privcmd.c Tue Jun 24 21:02:47 2008 +0100
@@ -93,13 +93,16 @@ static long privcmd_ioctl(struct file *f
break;
case IOCTL_PRIVCMD_MMAP: {
+#define MMAP_NR_PER_PAGE (int)((PAGE_SIZE-sizeof(struct
list_head))/sizeof(privcmd_mmap_entry_t))
privcmd_mmap_t mmapcmd;
- privcmd_mmap_entry_t msg;
+ privcmd_mmap_entry_t *msg;
privcmd_mmap_entry_t __user *p;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long va;
int i, rc;
+ LIST_HEAD(pagelist);
+ struct list_head *l,*l2;
if (!is_initial_xendomain())
return -EPERM;
@@ -108,63 +111,92 @@ static long privcmd_ioctl(struct file *f
return -EFAULT;
p = mmapcmd.entry;
- if (copy_from_user(&msg, p, sizeof(msg)))
- return -EFAULT;
+ for (i = 0; i < mmapcmd.num;) {
+ int nr = min(mmapcmd.num - i, MMAP_NR_PER_PAGE);
+
+ rc = -ENOMEM;
+ l = (struct list_head *) __get_free_page(GFP_KERNEL);
+ if (l == NULL)
+ goto mmap_out;
+
+ INIT_LIST_HEAD(l);
+ list_add_tail(l, &pagelist);
+ msg = (privcmd_mmap_entry_t*)(l + 1);
+
+ rc = -EFAULT;
+ if (copy_from_user(msg, p, nr*sizeof(*msg)))
+ goto mmap_out;
+ i += nr;
+ p += nr;
+ }
+
+ l = pagelist.next;
+ msg = (privcmd_mmap_entry_t*)(l + 1);
down_write(&mm->mmap_sem);
- vma = find_vma(mm, msg.va);
+ vma = find_vma(mm, msg->va);
rc = -EINVAL;
- if (!vma || (msg.va != vma->vm_start) ||
+ if (!vma || (msg->va != vma->vm_start) ||
!privcmd_enforce_singleshot_mapping(vma))
goto mmap_out;
va = vma->vm_start;
- for (i = 0; i < mmapcmd.num; i++) {
- rc = -EFAULT;
- if (copy_from_user(&msg, p, sizeof(msg)))
- goto mmap_out;
-
- /* Do not allow range to wrap the address space. */
- rc = -EINVAL;
- if ((msg.npages > (LONG_MAX >> PAGE_SHIFT)) ||
- ((unsigned long)(msg.npages << PAGE_SHIFT) >= -va))
- goto mmap_out;
-
- /* Range chunks must be contiguous in va space. */
- if ((msg.va != va) ||
- ((msg.va+(msg.npages<<PAGE_SHIFT)) > vma->vm_end))
- goto mmap_out;
-
- if ((rc = direct_remap_pfn_range(
- vma,
- msg.va & PAGE_MASK,
- msg.mfn,
- msg.npages << PAGE_SHIFT,
- vma->vm_page_prot,
- mmapcmd.dom)) < 0)
- goto mmap_out;
-
- p++;
- va += msg.npages << PAGE_SHIFT;
+ i = 0;
+ list_for_each(l, &pagelist) {
+ int nr = i + min(mmapcmd.num - i, MMAP_NR_PER_PAGE);
+
+ msg = (privcmd_mmap_entry_t*)(l + 1);
+ while (i<nr) {
+
+ /* Do not allow range to wrap the address
space. */
+ rc = -EINVAL;
+ if ((msg->npages > (LONG_MAX >> PAGE_SHIFT)) ||
+ ((unsigned long)(msg->npages << PAGE_SHIFT)
>= -va))
+ goto mmap_out;
+
+ /* Range chunks must be contiguous in va space.
*/
+ if ((msg->va != va) ||
+ ((msg->va+(msg->npages<<PAGE_SHIFT)) >
vma->vm_end))
+ goto mmap_out;
+
+ if ((rc = direct_remap_pfn_range(
+ vma,
+ msg->va & PAGE_MASK,
+ msg->mfn,
+ msg->npages << PAGE_SHIFT,
+ vma->vm_page_prot,
+ mmapcmd.dom)) < 0)
+ goto mmap_out;
+
+ va += msg->npages << PAGE_SHIFT;
+ msg++;
+ i++;
+ }
}
rc = 0;
mmap_out:
up_write(&mm->mmap_sem);
+ list_for_each_safe(l,l2,&pagelist)
+ free_page((unsigned long)l);
ret = rc;
}
+#undef MMAP_NR_PER_PAGE
break;
case IOCTL_PRIVCMD_MMAPBATCH: {
+#define MMAPBATCH_NR_PER_PAGE (unsigned long)((PAGE_SIZE-sizeof(struct
list_head))/sizeof(unsigned long))
privcmd_mmapbatch_t m;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
xen_pfn_t __user *p;
- unsigned long addr, mfn, nr_pages;
+ unsigned long addr, *mfn, nr_pages;
int i;
+ LIST_HEAD(pagelist);
+ struct list_head *l, *l2;
if (!is_initial_xendomain())
return -EPERM;
@@ -176,34 +208,74 @@ static long privcmd_ioctl(struct file *f
if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
return -EINVAL;
+ p = m.arr;
+ for (i=0; i<nr_pages; ) {
+ int nr = min(nr_pages - i, MMAPBATCH_NR_PER_PAGE);
+
+ ret = -ENOMEM;
+ l = (struct list_head *)__get_free_page(GFP_KERNEL);
+ if (l == NULL)
+ goto mmapbatch_out;
+
+ INIT_LIST_HEAD(l);
+ list_add_tail(l, &pagelist);
+
+ mfn = (unsigned long*)(l + 1);
+ ret = -EFAULT;
+ if (copy_from_user(mfn, p, nr*sizeof(*mfn)))
+ goto mmapbatch_out;
+
+ i += nr; p+= nr;
+ }
+
down_write(&mm->mmap_sem);
vma = find_vma(mm, m.addr);
+ ret = -EINVAL;
if (!vma ||
(m.addr != vma->vm_start) ||
((m.addr + (nr_pages << PAGE_SHIFT)) != vma->vm_end) ||
!privcmd_enforce_singleshot_mapping(vma)) {
up_write(&mm->mmap_sem);
- return -EINVAL;
+ goto mmapbatch_out;
}
p = m.arr;
addr = m.addr;
- for (i = 0; i < nr_pages; i++, addr += PAGE_SIZE, p++) {
- if (get_user(mfn, p)) {
- up_write(&mm->mmap_sem);
- return -EFAULT;
+ i = 0;
+ ret = 0;
+ list_for_each(l, &pagelist) {
+ int nr = i + min(nr_pages - i, MMAPBATCH_NR_PER_PAGE);
+ mfn = (unsigned long *)(l + 1);
+
+ while (i<nr) {
+ if(direct_remap_pfn_range(vma, addr & PAGE_MASK,
+ *mfn, PAGE_SIZE,
+ vma->vm_page_prot,
m.dom) < 0) {
+ *mfn |= 0xf0000000U;
+ ret++;
+ }
+ mfn++; i++; addr += PAGE_SIZE;
}
-
- ret = direct_remap_pfn_range(vma, addr & PAGE_MASK,
- mfn, PAGE_SIZE,
- vma->vm_page_prot, m.dom);
- if (ret < 0)
- put_user(0xF0000000 | mfn, p);
}
up_write(&mm->mmap_sem);
- ret = 0;
+ if (ret > 0) {
+ p = m.arr;
+ i = 0;
+ ret = 0;
+ list_for_each(l, &pagelist) {
+ int nr = min(nr_pages - i,
MMAPBATCH_NR_PER_PAGE);
+ mfn = (unsigned long *)(l + 1);
+ if (copy_to_user(p, mfn, nr*sizeof(*mfn)))
+ ret = -EFAULT;
+ i += nr; p += nr;
+ }
+ }
+ mmapbatch_out:
+ list_for_each_safe(l,l2,&pagelist)
+ free_page((unsigned long)l);
+#undef MMAPBATCH_NR_PER_PAGE
}
break;
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