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um: fix ubd cow size

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ubd_file_size() cannot use ubd_dev->cow.file because at this time
ubd_dev->cow.file is not initialized.
Therefore, ubd_file_size() will always report a wrong disk size when
COW files are used.
Reading from /dev/ubd* would crash the kernel.

We have to read the correct disk size from the COW file's backing
file.

Signed-off-by: Richard Weinberger <richard@nod.at>
CC: stable@kernel.org
This commit is contained in:
Richard Weinberger 2011-11-02 13:17:27 +01:00
parent 0d65ede0a6
commit 8535639810
1 changed files with 30 additions and 1 deletions
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31
arch/um/drivers/ubd_kern.c
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@ -511,8 +511,37 @@ __uml_exitcall(kill_io_thread);
static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
{
char *file;
int fd;
int err;
file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
__u32 version;
__u32 align;
char *backing_file;
time_t mtime;
unsigned long long size;
int sector_size;
int bitmap_offset;
if (ubd_dev->file && ubd_dev->cow.file) {
file = ubd_dev->cow.file;
goto out;
}
fd = os_open_file(ubd_dev->file, global_openflags, 0);
if (fd < 0)
return fd;
err = read_cow_header(file_reader, &fd, &version, &backing_file, \
&mtime, &size, &sector_size, &align, &bitmap_offset);
os_close_file(fd);
if(err == -EINVAL)
file = ubd_dev->file;
else
file = backing_file;
out:
return os_file_size(file, size_out);
}