[patch] ext2_fill_super breakage

Andrew Morton
2002-03-28T07:32:28Z

In 2.5.7 there is a thinko in the allocation and initialisation
of the fs-private superblock for ext2. It's passing the wrong type
to the sizeof operator (which of course gives the wrong size)
when allocating and clearing the memory.

Lesson for the day: this is one of the reasons why this idiom:

some_type *p;

p = malloc(sizeof(*p));
...
memset(p, 0, sizeof(*p));

is preferable to

some_type *p;

p = malloc(sizeof(some_type));
...
memset(p, 0, sizeof(some_type));

I checked the other filesystems. They're OK (but idiomatically
impure). I've added a couple of defensive memsets where
they were missing.

--- 2.5.7/fs/autofs/inode.c~fill-super Wed Mar 27 23:14:20 2002
+++ 2.5.7-akpm/fs/autofs/inode.c Wed Mar 27 23:14:54 2002
@@ -119,9 +119,10 @@ int autofs_fill_super(struct super_block
struct autofs_sb_info *sbi;
int minproto, maxproto;

- sbi = (struct autofs_sb_info *) kmalloc(sizeof(struct autofs_sb_info), GFP_KERNEL);
+ sbi = kmalloc(sizeof(*sbi), GFP_KERNEL);
if ( !sbi )
goto fail_unlock;
+ memset(sbi, 0, sizeof(*sbi));
DPRINTK(("autofs: starting up, sbi = %p\n",sbi));

s->u.generic_sbp = sbi;
--- 2.5.7/fs/devpts/inode.c~fill-super Wed Mar 27 23:16:05 2002
+++ 2.5.7-akpm/fs/devpts/inode.c Wed Mar 27 23:16:33 2002
@@ -123,9 +123,10 @@ static int devpts_fill_super(struct supe
struct inode * inode;
struct devpts_sb_info *sbi;

- sbi = (struct devpts_sb_info *) kmalloc(sizeof(struct devpts_sb_info), GFP_KERNEL);
+ sbi = kmalloc(sizeof(*sbi), GFP_KERNEL);
if ( !sbi )
goto fail;
+ memset(sbi, 0, sizeof(*sbi));

sbi->magic = DEVPTS_SBI_MAGIC;
sbi->max_ptys = unix98_max_ptys;
--- 2.5.7/fs/ext2/super.c~fill-super Wed Mar 27 23:16:57 2002
+++ 2.5.7-akpm/fs/ext2/super.c Wed Mar 27 23:17:25 2002
@@ -465,11 +465,11 @@ static int ext2_fill_super(struct super_
int db_count;
int i, j;

- sbi = kmalloc(sizeof(struct ext2_super_block), GFP_KERNEL);
+ sbi = kmalloc(sizeof(*sbi), GFP_KERNEL);
if (!sbi)
return -ENOMEM;
sb->u.generic_sbp = sbi;
- memset(sbi, 0, sizeof(struct ext2_super_block));
+ memset(sbi, 0, sizeof(*sbi));

/*
* See what the current blocksize for the device is, and

-