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 <mtosatti@redhat.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6dc0334815f7f1243691ff714b175e2bc2b4dd54..4206454734e09d464d34a5c5a3bd86a6b51cfa9d 100644 (file)
--- 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: