[lkml]   [2018]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH] dm ioctl: fix a missing-check bug
In copy_params(), the struct 'dm_ioctl' is firstly copied from the user
space buffer 'user' to 'param_kernel' and the field 'data_size' is checked
against 'minimum_data_size'. If the check fails, an error code EINVAL will
be returned. Otherwise, the 'data_size' is used to do the second copy,
which copies from the same user-space buffer to 'dmi'. After the second
copy, only 'dmi->data_size' is checked against 'param_kernel->data_size'.
Given that the buffer 'user' resides in the user space, a malicious
user-space process can race to change the content in the buffer between the
two copies. This way, the attacker can inject inconsistent data in
'param_kernel' and 'dmi'.

This patch removes the redundant part in the second copy and reuses the
result in the first copy. It also remove the check of 'data_size' after the
second copy because it is unnecessary with this patch.

Signed-off-by: Wenwen Wang <>
drivers/md/dm-ioctl.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index b810ea7..b708c69 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1762,18 +1762,13 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern

*param_flags |= DM_PARAMS_MALLOC;

- if (copy_from_user(dmi, user, param_kernel->data_size))
+ if (copy_from_user(&dmi->data, (char __user *)user + minimum_data_size,
+ param_kernel->data_size - minimum_data_size))
goto bad;

- /*
- * Abort if something changed the ioctl data while it was being copied.
- */
- if (dmi->data_size != param_kernel->data_size) {
- DMERR("rejecting ioctl: data size modified while processing parameters");
- goto bad;
- }
+ memcpy(dmi, param_kernel, minimum_data_size);

/* Wipe the user buffer so we do not return it to userspace */
if (secure_data && clear_user(user, param_kernel->data_size))
goto bad;
 \ /
  Last update: 2018-10-03 18:45    [W:0.021 / U:1.668 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site