loop: cleanup set_status interface
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>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 0d56739..68b205a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -161,17 +161,19 @@
&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 @@
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 @@
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 @@
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 @@
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);