[PATCH 2/3] procfs: Call default get_unmapped_area on MMU-presentarchitectures

[HATAYAMA Daisuke]

commit c4fe24485729fc2cbff324c111e67a1cc2f9adea 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 defiend 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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---
 fs/proc/inode.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 6c501c4..8eaa1ba 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);

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