Messages in this thread Patch in this message | | | Date | Wed, 27 Mar 2002 23:30:22 -0800 | From | Andrew Morton <> | Subject | [patch] ext2_fill_super breakage |
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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
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