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>

1 files changed, 13 insertions, 5 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6dc0334815f7..4206454734e0 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: