2008-03-08 23:33:01

by Marcelo Tosatti

Subject: [PATCH] pagemap: proper read error handling

Fix pagemap_read() error handling by releasing acquired resources and
checking for get_user_pages() partial failure.

Signed-off-by: Marcelo Tosatti <[email protected]>


diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6dc0334..4206454 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -640,17 +640,17 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,

ret = -EACCES;
if (!ptrace_may_attach(task))
- goto out;
+ goto out_task;

ret = -EINVAL;
/* file position must be aligned */
if (*ppos % PM_ENTRY_BYTES)
- goto out;
+ goto out_task;

ret = 0;
mm = get_task_mm(task);
if (!mm)
- goto out;
+ goto out_task;

ret = -ENOMEM;
uaddr = (unsigned long)buf & PAGE_MASK;
@@ -658,7 +658,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
pagecount = (PAGE_ALIGN(uend) - uaddr) / PAGE_SIZE;
pages = kmalloc(pagecount * sizeof(struct page *), GFP_KERNEL);
if (!pages)
- goto out_task;
+ goto out_mm;

down_read(&current->mm->mmap_sem);
ret = get_user_pages(current, current->mm, uaddr, pagecount,
@@ -668,6 +668,12 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (ret < 0)
goto out_free;

+ if (ret != pagecount) {
+ pagecount = ret;
+ ret = -EFAULT;
+ goto out_pages;
+ }
+
pm.out = buf;
pm.end = buf + count;

@@ -699,15 +705,17 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
ret = pm.out - buf;
}

+out_pages:
for (; pagecount; pagecount--) {
page = pages[pagecount-1];
if (!PageReserved(page))
SetPageDirty(page);
page_cache_release(page);
}
- mmput(mm);
out_free:
kfree(pages);
+out_mm:
+ mmput(mm);
out_task:
put_task_struct(task);
out:

2008-03-10 18:33:14

by Matt Mackall

Subject: Re: [PATCH] pagemap: proper read error handling

On Sat, 2008-03-08 at 20:35 -0300, Marcelo Tosatti wrote:
> Fix pagemap_read() error handling by releasing acquired resources and
> checking for get_user_pages() partial failure.
>
> Signed-off-by: Marcelo Tosatti <[email protected]>

Thanks, Marcelo, this all looks good.

Signed-off-by: Matt Mackall <[email protected]>

> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 6dc0334..4206454 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -640,17 +640,17 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
>
> ret = -EACCES;
> if (!ptrace_may_attach(task))
> - goto out;
> + goto out_task;
>
> ret = -EINVAL;
> /* file position must be aligned */
> if (*ppos % PM_ENTRY_BYTES)
> - goto out;
> + goto out_task;
>
> ret = 0;
> mm = get_task_mm(task);
> if (!mm)
> - goto out;
> + goto out_task;
>
> ret = -ENOMEM;
> uaddr = (unsigned long)buf & PAGE_MASK;
> @@ -658,7 +658,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
> pagecount = (PAGE_ALIGN(uend) - uaddr) / PAGE_SIZE;
> pages = kmalloc(pagecount * sizeof(struct page *), GFP_KERNEL);
> if (!pages)
> - goto out_task;
> + goto out_mm;
>
> down_read(&current->mm->mmap_sem);
> ret = get_user_pages(current, current->mm, uaddr, pagecount,
> @@ -668,6 +668,12 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
> if (ret < 0)
> goto out_free;
>
> + if (ret != pagecount) {
> + pagecount = ret;
> + ret = -EFAULT;
> + goto out_pages;
> + }
> +
> pm.out = buf;
> pm.end = buf + count;
>
> @@ -699,15 +705,17 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
> ret = pm.out - buf;
> }
>
> +out_pages:
> for (; pagecount; pagecount--) {
> page = pages[pagecount-1];
> if (!PageReserved(page))
> SetPageDirty(page);
> page_cache_release(page);
> }
> - mmput(mm);
> out_free:
> kfree(pages);
> +out_mm:
> + mmput(mm);
> out_task:
> put_task_struct(task);
> out:
--
Mathematics is the supreme nostalgia of our time.