Re: [RFC] block_dev:Fix bug when read/write block-device which is larger than 16TB in 32bit-OS.

[majianpeng <majianpeng@gmail.com>]

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On 2012-05-29 16:56 majianpeng <majianpeng@gmail.com> Wrote:
>The size of block-device is larger than 16TB, and the os is 32bit.
>If the offset of read/write is larger then 16TB. The index of address_space will
>overflow and supply data from low offset instead.
>
>when read-operation, in function do_generic_file_read():
>>index = *ppos >> PAGE_CACHE_SHIFT;
>Because the *ppos is larger than 16TB and the index  is the type pgoff_t which 32bit
>in 32bit-OS. So index will overflow.
>
>When write-operation, in function generic_write_checks():
>>if (likely(!isblk)) {
>>		.....
>>	} else {
>>#ifdef CONFIG_BLOCK
>>		loff_t isize;
>>		if (bdev_read_only(I_BDEV(inode)))
>			return -EPERM;
>>		isize = i_size_read(inode);
>>		if (*pos >= isize) {
>>			if (*count || *pos > isize)
>>				return -ENOSPC;
>>		}
>>
>>		if (*pos + *count > isize)
>>			*count = isize - *pos;
>The code only check size.But continue code:
>generic_file_buffered_write-->generic_perform_write-->blkdev_write_begin 
>--->block_write_begin()
>> pgoff_t index = pos >> PAGE_CACHE_SHIFT;
>The index will overflow again.
>
>Although filesystem has a attribute s_maxbytes, the block-device was not create so no affect.
>
>
>Signed-off-by: majianpeng <majianpeng@gmail.com>
>---
> fs/block_dev.c |    4 +++-
> mm/filemap.c   |   28 ++++++++++++++++++++++++++++
> 2 files changed, 31 insertions(+), 1 deletion(-)
>
>diff --git a/fs/block_dev.c b/fs/block_dev.c
>index c2bbe1f..1752c0e 100644
>--- a/fs/block_dev.c
>+++ b/fs/block_dev.c
>@@ -382,7 +382,9 @@ static loff_t block_llseek(struct file *file, loff_t offset, int origin)
> 
> 	mutex_lock(&bd_inode->i_mutex);
> 	size = i_size_read(bd_inode);
>-
>+#if BITS_PER_LONG == 32
>+	size = min_t(loff_t, size, (loff_t)0xFFFFFFFF * PAGE_CACHE_SIZE - 1);
>+#endif
> 	retval = -EINVAL;
> 	switch (origin) {
> 		case SEEK_END:
>diff --git a/mm/filemap.c b/mm/filemap.c
>index 79c4b2b..34a15bf 100644
>--- a/mm/filemap.c
>+++ b/mm/filemap.c
>@@ -1373,6 +1373,25 @@ int generic_segment_checks(const struct iovec *iov,
> }
> EXPORT_SYMBOL(generic_segment_checks);
> 
>+static inline
>+int generic_read_block_checks(struct file *file, loff_t *pos, size_t *count)
>+{
>+	struct inode *inode = file->f_mapping->host;
>+	loff_t isize = 0;
>+#if BITS_PER_LONG == 32 && defined(CONFIG_BLOCK)
>+	isize = min_t(loff_t, i_size_read(inode),
>+			(loff_t)0xFFFFFFFF * PAGE_CACHE_SIZE - 1);
>+	if (*pos >= isize) {
>+		if (*count || *pos > isize)
>+			return -ENOSPC;
>+	}
>+
>+	if (*pos + *count > isize)
>+		*count = isize - *pos;
>+#endif
>+	return 0;
>+}
>+
> /**
>  * generic_file_aio_read - generic filesystem read routine
>  * @iocb:	kernel I/O control block
>@@ -1398,6 +1417,11 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
> 	if (retval)
> 		return retval;
> 
>+	if (S_ISBLK(filp->f_mapping->host->i_mode)) {
>+		retval = generic_read_block_checks(filp, &pos, &count);
>+		if (retval)
>+			return retval;
>+	}
> 	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
> 	if (filp->f_flags & O_DIRECT) {
> 		loff_t size;
>@@ -2214,6 +2238,10 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i
> 		if (bdev_read_only(I_BDEV(inode)))
> 			return -EPERM;
> 		isize = i_size_read(inode);
>+#if BITS_PER_LONG == 32
>+		isize = min_t(loff_t, isize,
>+				(loff_t)0xFFFFFFFF * PAGE_CACHE_SIZE - 1);
>+#endif
> 		if (*pos >= isize) {
> 			if (*count || *pos > isize)
> 				return -ENOSPC;
>-- 
>1.7.9.5

How about this patch? ok or error ?
No one to reply? Maybe the patch did no sense.

Thansk!
>
> 				
>--------------
>majianpeng
>2012-05-29N‹§²æìr¸›zǧu©ž²Æ {\b­†éì¹»\x1c®&Þ–)îÆi¢žØ^n‡r¶‰šŽŠÝ¢j$½§$¢¸\x05¢¹¨­è§~Š'.)îÄÃ,yèm¶ŸÿÃ\f%Š{±šj+ƒðèž×¦j)Z†·Ÿ