linux-kernel - [PATCH] proc: put check_mem_permission before __get_free_page in mem

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Date:	Sun, 17 Apr 2011 20:20:01 -0400
From:	bookjovi@...il.com
To:	bookjovi@...il.com
Cc:	Andrew Morton <akpm@...ux-foundation.org> (commit_signer:19/51=37%),
	Al Viro <viro@...iv.linux.org.uk> (commit_signer:17/51=33%),
	David Rientjes <rientjes@...gle.com> (commit_signer:7/51=14%),
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> (commit_signer:5/51=10%),
	Stephen Wilson <wilsons@...rt.ca> (commit_signer:4/51=8%),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] proc: put check_mem_permission before __get_free_page in mem_read

From: Jovi Zhang <bookjovi@...il.com>

It should be better if put check_mem_permission before __get_free_page
in mem_read, to be same as function mem_write.

Signed-off-by: Jovi Zhang <bookjovi@...il.com>
---
 fs/proc/base.c |   24 ++++++++++--------------
 1 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index dfa5327..d66126d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -831,23 +831,21 @@ static ssize_t mem_read(struct file * file, char __user * buf,
 	if (!task)
 		goto out_no_task;
 
-	ret = -ENOMEM;
-	page = (char *)__get_free_page(GFP_TEMPORARY);
-	if (!page)
-		goto out;
-
 	mm = check_mem_permission(task);
 	ret = PTR_ERR(mm);
 	if (IS_ERR(mm))
-		goto out_free;
+		goto out_task;
 
 	ret = -EIO;
- 
 	if (file->private_data != (void*)((long)current->self_exec_id))
-		goto out_put;
+		goto out_mm;
+
+	ret = -ENOMEM;
+	page = (char *)__get_free_page(GFP_TEMPORARY);
+	if (!page)
+		goto out_mm;
 
 	ret = 0;
- 
 	while (count > 0) {
 		int this_len, retval;
 
@@ -870,12 +868,10 @@ static ssize_t mem_read(struct file * file, char __user * buf,
 		count -= retval;
 	}
 	*ppos = src;
-
-out_put:
-	mmput(mm);
-out_free:
 	free_page((unsigned long) page);
-out:
+out_mm:
+	mmput(mm);
+out_task:
 	put_task_struct(task);
 out_no_task:
 	return ret;
-- 
1.7.2.3

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