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Subject[patch 04/18] remap_file_pages protection support: cleanup syscall checks
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From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

This patch reorganizes the code only, without differences in behaviour. It
makes the code more readable on its own, and is needed for next patches. I've
split this out to avoid cluttering real patches.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
---

linux-2.6.git-paolo/mm/fremap.c | 38 ++++++++++++++++++++++++--------------
1 files changed, 24 insertions(+), 14 deletions(-)

diff -puN mm/fremap.c~rfp-cleanup-sc-check mm/fremap.c
--- linux-2.6.git/mm/fremap.c~rfp-cleanup-sc-check 2005-08-24 10:45:48.000000000 +0200
+++ linux-2.6.git-paolo/mm/fremap.c 2005-08-24 11:21:13.000000000 +0200
@@ -178,7 +178,7 @@ err_unlock:
* future.
*/
asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
- unsigned long __prot, unsigned long pgoff, unsigned long flags)
+ unsigned long prot, unsigned long pgoff, unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct address_space *mapping;
@@ -186,9 +186,10 @@ asmlinkage long sys_remap_file_pages(uns
struct vm_area_struct *vma;
int err = -EINVAL;
int has_write_lock = 0;
+ pgprot_t pgprot;

- if (__prot)
- return err;
+ if (prot)
+ goto out;
/*
* Sanitize the syscall parameters:
*/
@@ -197,7 +198,7 @@ asmlinkage long sys_remap_file_pages(uns

/* Does the address range wrap, or is the span zero-sized? */
if (start + size <= start)
- return err;
+ goto out;

/* Can we represent this offset inside this architecture's pte's? */
#if PTE_FILE_MAX_BITS < BITS_PER_LONG
@@ -207,7 +208,7 @@ asmlinkage long sys_remap_file_pages(uns

/* We need down_write() to change vma->vm_flags. */
down_read(&mm->mmap_sem);
- retry:
+retry:
vma = find_vma(mm, start);

/*
@@ -217,13 +218,20 @@ asmlinkage long sys_remap_file_pages(uns
* swapout cursor in a VM_NONLINEAR vma (unless VM_RESERVED
* or VM_LOCKED, but VM_LOCKED could be revoked later on).
*/
- if (vma && (vma->vm_flags & VM_SHARED) &&
- (!vma->vm_private_data ||
- (vma->vm_flags & (VM_NONLINEAR|VM_RESERVED))) &&
- vma->vm_ops && vma->vm_ops->populate &&
- end > start && start >= vma->vm_start &&
- end <= vma->vm_end) {
+ if (!vma)
+ goto out_unlock;
+
+ if (!(vma->vm_flags & VM_SHARED))
+ goto out_unlock;

+ if (!vma->vm_ops || !vma->vm_ops->populate || end <= start || start <
+ vma->vm_start || end > vma->vm_end)
+ goto out_unlock;
+
+ pgprot = vma->vm_page_prot;
+
+ if (!vma->vm_private_data ||
+ (vma->vm_flags & (VM_NONLINEAR|VM_RESERVED))) {
/* Must set VM_NONLINEAR before any pages are populated. */
if (pgoff != linear_page_index(vma, start) &&
!(vma->vm_flags & VM_NONLINEAR)) {
@@ -249,16 +257,18 @@ asmlinkage long sys_remap_file_pages(uns
downgrade_write(&mm->mmap_sem);
has_write_lock = 0;
}
- err = vma->vm_ops->populate(vma, start, size,
- vma->vm_page_prot,
- pgoff, flags & MAP_NONBLOCK);
+ err = vma->vm_ops->populate(vma, start, size, pgprot, pgoff,
+ flags & MAP_NONBLOCK);

}
+
+out_unlock:
if (likely(!has_write_lock))
up_read(&mm->mmap_sem);
else
up_write(&mm->mmap_sem);

+out:
return err;
}

_
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