Re: [PATCH v3] fs/minix: Verify bitmap block counts before mounting

Josh Boyer
2011-09-29T18:38:22Z

On Fri, Aug 19, 2011 at 02:50:25PM -0400, Josh Boyer wrote:
> Newer versions of MINIX can create filesystems that allocate an extra
> bitmap block. Mounting of this succeeds, but doing a statfs call will
> result in an oops in count_free because of a negative number being used
> for the bh index.
>
> Avoid this by verifying the number of allocated blocks at mount time,
> erroring out if there are not enough and make statfs ignore the extras
> if there are too many.
>
> This fixes https://bugzilla.kernel.org/show_bug.cgi?id=18792
>
> Signed-off-by: Josh Boyer <jwboyer@redhat.com>

Al, did this ever get queued up to send to Linus?

josh

> ---
> v3: Pass blocksize to count_free itself and get rid of open coded DIV_ROUND_UP
> v2: Remove some thinko stupidity and silently ignore the too many blocks case
>
> fs/minix/bitmap.c | 18 ++++++++++++------
> fs/minix/inode.c | 25 +++++++++++++++++++++++--
> fs/minix/minix.h | 9 +++++++--
> 3 files changed, 42 insertions(+), 10 deletions(-)
>
> diff --git a/fs/minix/bitmap.c b/fs/minix/bitmap.c
> index 3f32bcb..7c82c29 100644
> --- a/fs/minix/bitmap.c
> +++ b/fs/minix/bitmap.c
> @@ -20,10 +20,11 @@ static const int nibblemap[] = { 4,3,3,2,3,2,2,1,3,2,2,1,2,1,1,0 };
>
> static DEFINE_SPINLOCK(bitmap_lock);
>
> -static unsigned long count_free(struct buffer_head *map[], unsigned numblocks, __u32 numbits)
> +static unsigned long count_free(struct buffer_head *map[], unsigned blocksize, __u32 numbits)
> {
> unsigned i, j, sum = 0;
> struct buffer_head *bh;
> + unsigned numblocks = minix_blocks_needed(numbits, blocksize);
>
> for (i=0; i<numblocks-1; i++) {
> if (!(bh=map[i]))
> @@ -105,10 +106,12 @@ int minix_new_block(struct inode * inode)
> return 0;
> }
>
> -unsigned long minix_count_free_blocks(struct minix_sb_info *sbi)
> +unsigned long minix_count_free_blocks(struct super_block *sb)
> {
> - return (count_free(sbi->s_zmap, sbi->s_zmap_blocks,
> - sbi->s_nzones - sbi->s_firstdatazone + 1)
> + struct minix_sb_info *sbi = minix_sb(sb);
> + u32 bits = sbi->s_nzones - (sbi->s_firstdatazone + 1);
> +
> + return (count_free(sbi->s_zmap, sb->s_blocksize, bits)
> << sbi->s_log_zone_size);
> }
>
> @@ -273,7 +276,10 @@ struct inode *minix_new_inode(const struct inode *dir, int mode, int *error)
> return inode;
> }
>
> -unsigned long minix_count_free_inodes(struct minix_sb_info *sbi)
> +unsigned long minix_count_free_inodes(struct super_block *sb)
> {
> - return count_free(sbi->s_imap, sbi->s_imap_blocks, sbi->s_ninodes + 1);
> + struct minix_sb_info *sbi = minix_sb(sb);
> + u32 bits = sbi->s_ninodes + 1;
> +
> + return count_free(sbi->s_imap, sb->s_blocksize, bits);
> }
> diff --git a/fs/minix/inode.c b/fs/minix/inode.c
> index e7d23e2..1ed1351 100644
> --- a/fs/minix/inode.c
> +++ b/fs/minix/inode.c
> @@ -279,6 +279,27 @@ static int minix_fill_super(struct super_block *s, void *data, int silent)
> else if (sbi->s_mount_state & MINIX_ERROR_FS)
> printk("MINIX-fs: mounting file system with errors, "
> "running fsck is recommended\n");
> +
> + /* Apparently minix can create filesystems that allocate more blocks for
> + * the bitmaps than needed. We simply ignore that, but verify it didn't
> + * create one with not enough blocks and bail out if so.
> + */
> + block = minix_blocks_needed(sbi->s_ninodes, s->s_blocksize);
> + if (sbi->s_imap_blocks < block) {
> + printk("MINIX-fs: file system does not have enough "
> + "imap blocks allocated. Refusing to mount\n");
> + goto out_iput;
> + }
> +
> + block = minix_blocks_needed(
> + (sbi->s_nzones - (sbi->s_firstdatazone + 1)),
> + s->s_blocksize);
> + if (sbi->s_zmap_blocks < block) {
> + printk("MINIX-fs: file system does not have enough "
> + "zmap blocks allocated. Refusing to mount.\n");
> + goto out_iput;
> + }
> +
> return 0;
>
> out_iput:
> @@ -339,10 +360,10 @@ static int minix_statfs(struct dentry *dentry, struct kstatfs *buf)
> buf->f_type = sb->s_magic;
> buf->f_bsize = sb->s_blocksize;
> buf->f_blocks = (sbi->s_nzones - sbi->s_firstdatazone) << sbi->s_log_zone_size;
> - buf->f_bfree = minix_count_free_blocks(sbi);
> + buf->f_bfree = minix_count_free_blocks(sb);
> buf->f_bavail = buf->f_bfree;
> buf->f_files = sbi->s_ninodes;
> - buf->f_ffree = minix_count_free_inodes(sbi);
> + buf->f_ffree = minix_count_free_inodes(sb);
> buf->f_namelen = sbi->s_namelen;
> buf->f_fsid.val[0] = (u32)id;
> buf->f_fsid.val[1] = (u32)(id >> 32);
> diff --git a/fs/minix/minix.h b/fs/minix/minix.h
> index 341e212..6415fe0 100644
> --- a/fs/minix/minix.h
> +++ b/fs/minix/minix.h
> @@ -48,10 +48,10 @@ extern struct minix_inode * minix_V1_raw_inode(struct super_block *, ino_t, stru
> extern struct minix2_inode * minix_V2_raw_inode(struct super_block *, ino_t, struct buffer_head **);
> extern struct inode * minix_new_inode(const struct inode *, int, int *);
> extern void minix_free_inode(struct inode * inode);
> -extern unsigned long minix_count_free_inodes(struct minix_sb_info *sbi);
> +extern unsigned long minix_count_free_inodes(struct super_block *sb);
> extern int minix_new_block(struct inode * inode);
> extern void minix_free_block(struct inode *inode, unsigned long block);
> -extern unsigned long minix_count_free_blocks(struct minix_sb_info *sbi);
> +extern unsigned long minix_count_free_blocks(struct super_block *sb);
> extern int minix_getattr(struct vfsmount *, struct dentry *, struct kstat *);
> extern int minix_prepare_chunk(struct page *page, loff_t pos, unsigned len);
>
> @@ -88,6 +88,11 @@ static inline struct minix_inode_info *minix_i(struct inode *inode)
> return list_entry(inode, struct minix_inode_info, vfs_inode);
> }
>
> +static inline unsigned minix_blocks_needed(unsigned bits, unsigned blocksize)
> +{
> + return DIV_ROUND_UP(bits, blocksize * 8);
> +}
> +
> #if defined(CONFIG_MINIX_FS_NATIVE_ENDIAN) && \
> defined(CONFIG_MINIX_FS_BIG_ENDIAN_16BIT_INDEXED)
>
> --
> 1.7.6
>