linux-kernel - [PATCH] fs/proc/base.c: fix proc_fault_inject

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Date:	Fri, 14 Aug 2009 13:18:40 -0700
From:	Vincent Li <macli@....ubc.ca>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vincent Li <macli@....ubc.ca>
Subject: [PATCH] fs/proc/base.c: fix proc_fault_inject_write() input sanity check

Remove obfuscated zero-length input check and return -EINVAL instead of -EIO error
to make the error message clear to user. Add whitespace stripping. No functionality changes.

The old code:

echo  1  > /proc/pid/make-it-fail (ok)
echo 1foo > /proc/pid/make-it-fail (-bash: echo: write error: Input/output error)

The new code:

echo  1  > /proc/pid/make-it-fail (ok)
echo 1foo > /proc/pid/make-it-fail (-bash: echo: write error: Invalid argument)

This patch is conservative in changes to not breaking existing scripts/applications.
based on v2.6.31-rc6, compiled and tested ok.

Signed-off-by: Vincent Li <macli@....ubc.ca>
---
 fs/proc/base.c |   11 +++++------
 1 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 175db25..ba345d9 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1182,17 +1182,16 @@ static ssize_t proc_fault_inject_write(struct file * file,
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))
 		return -EFAULT;
-	make_it_fail = simple_strtol(buffer, &end, 0);
-	if (*end == '\n')
-		end++;
+	make_it_fail = simple_strtol(strstrip(buffer), &end, 0);
+	if (*end)
+		return -EINVAL;
 	task = get_proc_task(file->f_dentry->d_inode);
 	if (!task)
 		return -ESRCH;
 	task->make_it_fail = make_it_fail;
 	put_task_struct(task);
-	if (end - buffer == 0)
-		return -EIO;
-	return end - buffer;
+
+	return count;
 }
 
 static const struct file_operations proc_fault_inject_operations = {
-- 
1.6.0.4

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