linux-kernel - [PATCH] shmem: fix __shmem_file

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Date:   Mon, 27 Mar 2017 10:05:34 -0700
From:   Vito Caputo <vcaputo@...garu.com>
To:     hughd@...gle.com
Cc:     linux-kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: [PATCH] shmem: fix __shmem_file_setup error path leaks

The existing path and memory cleanups appear to be in reverse order, and
there's no iput() potentially leaking the inode in the last two error gotos.

Also make put_memory shmem_unacct_size() conditional on !inode since if we
entered cleanup at put_inode, shmem_evict_inode() occurs via
iput()->iput_final(), which performs the shmem_unacct_size() for us.

Signed-off-by: Vito Caputo <vcaputo@...garu.com>
---

This caught my eye while looking through the memfd_create() implementation.
Included patch was compile tested only...

 mm/shmem.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e67d6ba..a1a84eaf 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -4134,7 +4134,7 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
 				       unsigned long flags, unsigned int i_flags)
 {
 	struct file *res;
-	struct inode *inode;
+	struct inode *inode = NULL;
 	struct path path;
 	struct super_block *sb;
 	struct qstr this;
@@ -4162,7 +4162,7 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
 	res = ERR_PTR(-ENOSPC);
 	inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
 	if (!inode)
-		goto put_memory;
+		goto put_path;
 
 	inode->i_flags |= i_flags;
 	d_instantiate(path.dentry, inode);
@@ -4170,19 +4170,22 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
 	clear_nlink(inode);	/* It is unlinked */
 	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
 	if (IS_ERR(res))
-		goto put_path;
+		goto put_inode;
 
 	res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
 		  &shmem_file_operations);
 	if (IS_ERR(res))
-		goto put_path;
+		goto put_inode;
 
 	return res;
 
-put_memory:
-	shmem_unacct_size(flags, size);
+put_inode:
+	iput(inode);
 put_path:
 	path_put(&path);
+put_memory:
+	if (!inode)
+		shmem_unacct_size(flags, size);
 	return res;
 }
 
-- 
2.1.4