* [PATCH 2/2] revoke: break cow for private mappings
@ 2007-03-27 7:14 Pekka J Enberg
2007-03-28 8:04 ` Nick Piggin
0 siblings, 1 reply; 3+ messages in thread
From: Pekka J Enberg @ 2007-03-27 7:14 UTC (permalink / raw)
To: akpm; +Cc: linux-kernel
From: Pekka Enberg <penberg@cs.helsinki.fi>
We need to break COW for private mappings to make sure a process cannot
read new data after an inode has been revoked.
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
---
fs/revoke.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 73 insertions(+), 12 deletions(-)
Index: uml-2.6/fs/revoke.c
===================================================================
--- uml-2.6.orig/fs/revoke.c 2007-03-26 18:10:24.000000000 +0300
+++ uml-2.6/fs/revoke.c 2007-03-26 18:27:25.000000000 +0300
@@ -174,12 +174,58 @@ static inline bool need_revoke(struct vm
if (file->f_path.dentry->d_inode != inode)
return false;
- if (!(vma->vm_flags & VM_SHARED))
- return false;
-
return file != to_exclude;
}
+static int __revoke_break_cow(struct task_struct *tsk, struct inode *inode,
+ struct file *to_exclude)
+{
+ struct mm_struct *mm = tsk->mm;
+ struct vm_area_struct *vma;
+ int err = 0;
+
+ down_write(&mm->mmap_sem);
+ for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
+ int ret;
+
+ if (vma->vm_flags & VM_SHARED)
+ continue;
+
+ if (!need_revoke(vma, inode, to_exclude))
+ continue;
+
+ ret = get_user_pages(tsk, tsk->mm, vma->vm_start,
+ vma->vm_end-vma->vm_start, 1, 1, NULL,
+ NULL);
+ if (ret < 0) {
+ err = ret;
+ break;
+ }
+ }
+ up_write(&mm->mmap_sem);
+ return err;
+}
+
+static int revoke_break_cow(struct revoke_table *table, struct inode *inode,
+ struct file *to_exclude)
+{
+ unsigned long i;
+ int err = 0;
+
+ for (i = 0; i < table->end; i++) {
+ struct revokefs_inode_info *info;
+ struct file *this;
+
+ this = table->files[i];
+ info = revokefs_i(this->f_dentry->d_inode);
+
+ err = __revoke_break_cow(info->owner, inode, to_exclude);
+ if (err)
+ break;
+ }
+ return err;
+}
+
/*
* LOCKING: down_write(&mm->mmap_sem)
* -> spin_lock(&mapping->i_mmap_lock)
@@ -235,6 +281,9 @@ int err = 0;
goto out;
}
for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
+ if (!(vma->vm_flags & VM_SHARED))
+ continue;
+
if (!need_revoke(vma, mapping->host, to_exclude))
continue;
@@ -261,6 +310,9 @@ int try_again = 0;
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX) {
int err;
+ if (!(vma->vm_flags & VM_SHARED))
+ continue;
+
if (likely(!need_revoke(vma, mapping->host, to_exclude)))
continue;
@@ -380,12 +432,9 @@ for (i = 0; i < table->end; i++) {
put_task_struct(info->owner);
info->owner = NULL; /* To avoid restoring closed file. */
if (err)
- goto failed;
+ goto out;
}
- return 0;
-
- failed:
- restore_files(table);
+ out:
return err;
}
@@ -527,10 +576,8 @@ int err = 0;
exit_loop:
read_unlock(&tasklist_lock);
- if (err) {
- restore_files(table);
- goto out_free_table;
- }
+ if (err)
+ goto out_restore;
/*
* Take down shared memory mappings.
@@ -538,13 +585,27 @@ int err = 0;
revoke_mapping(inode->i_mapping, to_exclude);
/*
+ * Break COW for private mappings.
+ */
+ err = revoke_break_cow(table, inode, to_exclude);
+ if (err)
+ goto out_restore;
+
+ /*
* Now, revoke the files for good.
*/
err = revoke_files(table);
+ if (err)
+ goto out_restore;
+
out_free_table:
free_revoke_table(table);
out:
return err;
+
+ out_restore:
+ restore_files(table);
+ goto out_free_table;
}
asmlinkage long sys_revokeat(int dfd, const char __user * filename)
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 2/2] revoke: break cow for private mappings
2007-03-27 7:14 [PATCH 2/2] revoke: break cow for private mappings Pekka J Enberg
@ 2007-03-28 8:04 ` Nick Piggin
2007-03-28 10:09 ` Pekka Enberg
0 siblings, 1 reply; 3+ messages in thread
From: Nick Piggin @ 2007-03-28 8:04 UTC (permalink / raw)
To: Pekka J Enberg; +Cc: akpm, linux-kernel
Pekka J Enberg wrote:
> From: Pekka Enberg <penberg@cs.helsinki.fi>
>
> We need to break COW for private mappings to make sure a process cannot
> read new data after an inode has been revoked.
Seems OK.
>
> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
> ---
> fs/revoke.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 73 insertions(+), 12 deletions(-)
>
> Index: uml-2.6/fs/revoke.c
> ===================================================================
> --- uml-2.6.orig/fs/revoke.c 2007-03-26 18:10:24.000000000 +0300
> +++ uml-2.6/fs/revoke.c 2007-03-26 18:27:25.000000000 +0300
> @@ -174,12 +174,58 @@ static inline bool need_revoke(struct vm
> if (file->f_path.dentry->d_inode != inode)
> return false;
>
> - if (!(vma->vm_flags & VM_SHARED))
> - return false;
> -
> return file != to_exclude;
> }
>
> +static int __revoke_break_cow(struct task_struct *tsk, struct inode *inode,
> + struct file *to_exclude)
> +{
> + struct mm_struct *mm = tsk->mm;
> + struct vm_area_struct *vma;
> + int err = 0;
> +
> + down_write(&mm->mmap_sem);
> + for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
> + int ret;
> +
> + if (vma->vm_flags & VM_SHARED)
> + continue;
> +
> + if (!need_revoke(vma, inode, to_exclude))
> + continue;
> +
> + ret = get_user_pages(tsk, tsk->mm, vma->vm_start,
> + vma->vm_end-vma->vm_start, 1, 1, NULL,
> + NULL);
get_user_pages length argument is in # of pages, rather than address range,
I think. vma_pages is what you want?
> + if (ret < 0) {
> + err = ret;
> + break;
> + }
> + }
> + up_write(&mm->mmap_sem);
I think you just need down_read of mmap_sem here?
--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 2/2] revoke: break cow for private mappings
2007-03-28 8:04 ` Nick Piggin
@ 2007-03-28 10:09 ` Pekka Enberg
0 siblings, 0 replies; 3+ messages in thread
From: Pekka Enberg @ 2007-03-28 10:09 UTC (permalink / raw)
To: Nick Piggin; +Cc: akpm, linux-kernel
On 3/28/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> > + ret = get_user_pages(tsk, tsk->mm, vma->vm_start,
> > + vma->vm_end-vma->vm_start, 1, 1, NULL,
> > + NULL);
>
> get_user_pages length argument is in # of pages, rather than address range,
> I think. vma_pages is what you want?
Yes.
On 3/28/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> > + up_write(&mm->mmap_sem);
>
> I think you just need down_read of mmap_sem here?
Indeed. Thanks Nick.
Pekka
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2007-03-28 10:09 UTC | newest]
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2007-03-27 7:14 [PATCH 2/2] revoke: break cow for private mappings Pekka J Enberg
2007-03-28 8:04 ` Nick Piggin
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