linux-kernel - [PATCH] fs/proc/task_mmu.c v1: fix clear_refs

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Message-Id: <1250119794-8016-1-git-send-email-macli@brc.ubc.ca>
Date:	Wed, 12 Aug 2009 16:29:54 -0700
From:	Vincent Li <macli@....ubc.ca>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Vincent Li <macli@....ubc.ca>
Subject: [PATCH] fs/proc/task_mmu.c v1: fix clear_refs_write() input sanity check

v1 fix the compiling errors and keep the type variable name.

Andrew Morton pointed out similar string hacking and obfuscated check for zero-length input
at the end of the function, David Rientjes suggested to use strict_strtol to replace
simple_strtol, this patch cover above suggestions, add removing of leading and trailing
whitespace from user input. It does not change function behavious.

This patch is rebased on mmotm-2009-08-04-14-22.

Signed-off-by: Vincent Li <macli@....ubc.ca>
---
 fs/proc/task_mmu.c |   14 ++++++--------
 1 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 2079969..c7cf8f3 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -491,21 +491,20 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 				size_t count, loff_t *ppos)
 {
 	struct task_struct *task;
-	char buffer[PROC_NUMBUF], *end;
+	char buffer[PROC_NUMBUF];
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
-	int type;
+	long type;
 
 	memset(buffer, 0, sizeof(buffer));
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))
 		return -EFAULT;
-	type = simple_strtol(buffer, &end, 0);
+	if (strict_strtol(strstrip(buffer), 10, &type))
+		return -EINVAL;
 	if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
 		return -EINVAL;
-	if (*end == '\n')
-		end++;
 	task = get_proc_task(file->f_path.dentry->d_inode);
 	if (!task)
 		return -ESRCH;
@@ -541,9 +540,8 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 		mmput(mm);
 	}
 	put_task_struct(task);
-	if (end - buffer == 0)
-		return -EIO;
-	return end - buffer;
+
+	return count;
 }
 
 const struct file_operations proc_clear_refs_operations = {
-- 
1.6.0.4

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