Messages in this thread Patch in this message | | | From | Guo Chao <> | Subject | [PATCH 7/7] loopdev: ignore negative offset when calculate loop device size | Date | Fri, 25 Jan 2013 18:56:22 +0800 |
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Negative offset may cause loop device size larger than backing file size.
$ fallocate -l 1M a $ losetup --offset 0xffffffffffff0000 /dev/loop0 a $ blockdev --getsize64 /dev/loop0 1114112 $ ls -l a -rw-r--r-- 1 root root 1048576 Jan 23 12:46 a $ cat /dev/loop0 cat: /dev/loop0: Input/output error
It makes no sense to do that. Only apply offset when it's positive.
Fix a typo in the comment by the way.
Signed-off-by: Guo Chao <yan@linux.vnet.ibm.com> --- drivers/block/loop.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 9190a82..7a235db 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -162,12 +162,13 @@ static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = { static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file) { - loff_t size, loopsize; + loff_t loopsize; /* Compute loopsize in bytes */ - size = i_size_read(file->f_mapping->host); - loopsize = size - offset; - /* offset is beyond i_size, wierd but possible */ + loopsize = i_size_read(file->f_mapping->host); + if (offset > 0) + loopsize -= offset; + /* offset is beyond i_size, weird but possible */ if (loopsize < 0) return 0; -- 1.7.9.5
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