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loop: cleanup set_status interface

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1) Anyone who has read access to loopdev has permission to call set_status
   and may change important parameters such as lo_offset, lo_sizelimit and
   so on, which contradicts to read access pattern and definitely equals
   to write access pattern.
2) Add lo_offset over i_size check to prevent blkdev_size overflow.
   ##Testcase_bagin
   #dd if=/dev/zero of=./file bs=1k count=1
   #losetup /dev/loop0 ./file
   /* userspace_application */
   struct loop_info64 loinf;
   fd = open("/dev/loop0", O_RDONLY);
   ioctl(fd, LOOP_GET_STATUS64, &loinf);
   /* Set offset to any value which is bigger than i_size, and sizelimit
    * to nonzero value*/
   loinf.lo_offset = 4096*1024;
   loinf.lo_sizelimit = 1024;
   ioctl(fd, LOOP_SET_STATUS64, &loinf);
   /* After this loop device will have size similar to 0x7fffffffffxxxx */
   #blockdev --getsz /dev/loop0
   ##OUTPUT: 36028797018955968
   ##Testcase_end

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dmitry Monakhov 2011-11-16 09:21:49 +01:00 committed by Jens Axboe
parent 0c614e2d3e
commit 7035b5df3c
1 changed files with 30 additions and 16 deletions
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46
drivers/block/loop.c
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@ -161,17 +161,19 @@ static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
&xor_funcs
};
static loff_t get_loop_size(struct loop_device *lo, struct file *file)
static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
{
loff_t size, offset, loopsize;
loff_t size, loopsize;
/* Compute loopsize in bytes */
size = i_size_read(file->f_mapping->host);
offset = lo->lo_offset;
loopsize = size - offset;
if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
loopsize = lo->lo_sizelimit;
/* offset is beyond i_size, wierd but possible */
if (loopsize < 0)
return 0;
if (sizelimit > 0 && sizelimit < loopsize)
loopsize = sizelimit;
/*
* Unfortunately, if we want to do I/O on the device,
* the number of 512-byte sectors has to fit into a sector_t.
@ -179,17 +181,25 @@ static loff_t get_loop_size(struct loop_device *lo, struct file *file)
return loopsize >> 9;
}
static int
figure_loop_size(struct loop_device *lo)
static loff_t get_loop_size(struct loop_device *lo, struct file *file)
{
loff_t size = get_loop_size(lo, lo->lo_backing_file);
return get_size(lo->lo_offset, lo->lo_sizelimit, file);
}
static int
figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
{
loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
sector_t x = (sector_t)size;
if (unlikely((loff_t)x != size))
return -EFBIG;
if (lo->lo_offset != offset)
lo->lo_offset = offset;
if (lo->lo_sizelimit != sizelimit)
lo->lo_sizelimit = sizelimit;
set_capacity(lo->lo_disk, x);
return 0;
return 0;
}
static inline int
@ -1059,9 +1069,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
if (lo->lo_offset != info->lo_offset ||
lo->lo_sizelimit != info->lo_sizelimit) {
lo->lo_offset = info->lo_offset;
lo->lo_sizelimit = info->lo_sizelimit;
if (figure_loop_size(lo))
if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit))
return -EFBIG;
}
loop_config_discard(lo);
@ -1247,7 +1255,7 @@ static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
err = -ENXIO;
if (unlikely(lo->lo_state != Lo_bound))
goto out;
err = figure_loop_size(lo);
err = figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
if (unlikely(err))
goto out;
sec = get_capacity(lo->lo_disk);
@ -1285,13 +1293,19 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
goto out_unlocked;
break;
case LOOP_SET_STATUS:
err = loop_set_status_old(lo, (struct loop_info __user *) arg);
err = -EPERM;
if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
err = loop_set_status_old(lo,
(struct loop_info __user *)arg);
break;
case LOOP_GET_STATUS:
err = loop_get_status_old(lo, (struct loop_info __user *) arg);
break;
case LOOP_SET_STATUS64:
err = loop_set_status64(lo, (struct loop_info64 __user *) arg);
err = -EPERM;
if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
err = loop_set_status64(lo,
(struct loop_info64 __user *) arg);
break;
case LOOP_GET_STATUS64:
err = loop_get_status64(lo, (struct loop_info64 __user *) arg);