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ethtool: make .get_dump_data() harder to misuse by drivers

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As the patch "bnx2x: remove zeroing of dump data buffer" showed,
it is too easy implement .get_dump_data incorrectly in a driver.

Let's make sure drivers cannot get confused by userspace requesting
a too big dump.

Also WARN if the driver sets dump->len to something weird and make
sure the length reported to userspace is the actual length of data
copied to userspace.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michal Schmidt 2013-07-01 17:23:30 +02:00 committed by David S. Miller
parent 8cc2d927c2
commit c590b5e2f0
1 changed files with 20 additions and 1 deletions
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21
net/core/ethtool.c
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@ -1320,10 +1320,19 @@ static int ethtool_get_dump_data(struct net_device *dev,
if (ret)
return ret;
len = (tmp.len > dump.len) ? dump.len : tmp.len;
len = min(tmp.len, dump.len);
if (!len)
return -EFAULT;
/* Don't ever let the driver think there's more space available
* than it requested with .get_dump_flag().
*/
dump.len = len;
/* Always allocate enough space to hold the whole thing so that the
* driver does not need to check the length and bother with partial
* dumping.
*/
data = vzalloc(tmp.len);
if (!data)
return -ENOMEM;
@ -1331,6 +1340,16 @@ static int ethtool_get_dump_data(struct net_device *dev,
if (ret)
goto out;
/* There are two sane possibilities:
* 1. The driver's .get_dump_data() does not touch dump.len.
* 2. Or it may set dump.len to how much it really writes, which
* should be tmp.len (or len if it can do a partial dump).
* In any case respond to userspace with the actual length of data
* it's receiving.
*/
WARN_ON(dump.len != len && dump.len != tmp.len);
dump.len = len;
if (copy_to_user(useraddr, &dump, sizeof(dump))) {
ret = -EFAULT;
goto out;