linux-kernel - [PATCH] revoke: fix zero-length kmalloc

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Date:	Tue, 22 May 2007 23:05:13 +0300 (EEST)
From:	Pekka J Enberg <penberg@...helsinki.fi>
To:	akpm@...ux-foundation.org
cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] revoke: fix zero-length kmalloc

From: Pekka Enberg <penberg@...helsinki.fi>

Fix a zero-length kmalloc in the case where there is nothing to revoke.

Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
---
 fs/revoke.c |   21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

Index: 26-mm/fs/revoke.c
===================================================================
--- 26-mm.orig/fs/revoke.c	2007-05-22 22:58:17.000000000 +0300
+++ 26-mm/fs/revoke.c	2007-05-22 23:01:17.000000000 +0300
@@ -547,22 +547,12 @@ static struct fileset *__alloc_revoke_fs
 	return NULL;
 }
 
-static struct fileset *alloc_revoke_fset(struct inode *inode, struct file *to_exclude)
-{
-	unsigned long nr_fds;
-
-	read_lock(&tasklist_lock);
-	nr_fds = inode_fds(inode, to_exclude);
-	read_unlock(&tasklist_lock);
-
-	return __alloc_revoke_fset(nr_fds);
-}
-
 static int do_revoke(struct inode *inode, struct file *to_exclude)
 {
 	struct revoke_details details;
 	struct fileset *fset = NULL;
 	struct task_struct *g, *p;
+	unsigned long nr_fds;
 	int err = 0;
 
 	if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER)) {
@@ -576,11 +566,18 @@ static int do_revoke(struct inode *inode
 		goto out;
 	}
 
+	read_lock(&tasklist_lock);
+	nr_fds = inode_fds(inode, to_exclude);
+	read_unlock(&tasklist_lock);
+
+	if (!nr_fds)
+		goto out;
+
 	/*
 	 * Pre-allocate memory because the first pass is done under
 	 * tasklist_lock.
 	 */
-	fset = alloc_revoke_fset(inode, to_exclude);
+	fset = __alloc_revoke_fset(nr_fds);
 	if (!fset) {
 		err = -ENOMEM;
 		goto out;
-
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