procfs: call default get_unmapped_area on MMU-present architectures

Commit c4fe24485729 ("sparc: fix PCI device proc file mmap(2)") added
proc_reg_get_unmapped_area in proc_reg_file_ops and
proc_reg_file_ops_no_compat, by which now mmap always returns EIO if
get_unmapped_area method is not defined for the target procfs file,
which causes regression of mmap on /proc/vmcore.

To address this issue, like get_unmapped_area(), call default
current->mm->get_unmapped_area on MMU-present architectures if
pde->proc_fops->get_unmapped_area, i.e.  the one in actual file
operation in the procfs file, is not defined.

Reported-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Tested-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 6c501c4d996d..8eaa1ba793fc 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -289,9 +289,13 @@ static unsigned long proc_reg_get_unmapped_area(struct file *file, unsigned long
 {
         struct proc_dir_entry *pde = PDE(file_inode(file));
         unsigned long rv = -EIO;
-        unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
+        unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long) = NULL;
         if (use_pde(pde)) {
-                get_unmapped_area = pde->proc_fops->get_unmapped_area;
+#ifdef CONFIG_MMU
+                get_unmapped_area = current->mm->get_unmapped_area;
+#endif
+                if (pde->proc_fops->get_unmapped_area)
+                        get_unmapped_area = pde->proc_fops->get_unmapped_area;
                 if (get_unmapped_area)
                         rv = get_unmapped_area(file, orig_addr, len, pgoff, flags);
                 unuse_pde(pde);