diff options
| author | Wenwen Wang <wang6495@umn.edu> | 2018-10-03 11:43:59 -0500 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2018-10-18 11:54:07 -0400 |
| commit | 800a7340ab7dd667edf95e74d8e4f23a17e87076 (patch) | |
| tree | 661f1c6576b6862811a74b5431500c1487943b2f /drivers/md | |
| parent | bab5d988841e58fec6ae22f486905ddde2d715f4 (diff) | |
| download | linux-800a7340ab7dd667edf95e74d8e4f23a17e87076.tar.bz2 | |
dm ioctl: harden copy_params()'s copy_from_user() from malicious users
In copy_params(), the struct 'dm_ioctl' is first copied from the user
space buffer 'user' to 'param_kernel' and the field 'data_size' is
checked against 'minimum_data_size' (size of 'struct dm_ioctl' payload
up to its 'data' member). If the check fails, an error code EINVAL will be
returned. Otherwise, param_kernel->data_size is used to do a 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
into 'dmi' (versus previously validated 'param_kernel').
Fix redundant copying of 'minimum_data_size' from user-space buffer by
using the first copy stored in 'param_kernel'. Also remove the
'data_size' check after the second copy because it is now unnecessary.
Cc: stable@vger.kernel.org
Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm-ioctl.c | 18 |
1 files changed, 6 insertions, 12 deletions
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index b810ea77e6b1..f666778ad237 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1720,8 +1720,7 @@ static void free_params(struct dm_ioctl *param, size_t param_size, int param_fla } static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel, - int ioctl_flags, - struct dm_ioctl **param, int *param_flags) + int ioctl_flags, struct dm_ioctl **param, int *param_flags) { struct dm_ioctl *dmi; int secure_data; @@ -1762,18 +1761,13 @@ 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)) - goto bad; + /* Copy from param_kernel (which was already copied from user) */ + memcpy(dmi, param_kernel, minimum_data_size); -data_copied: - /* - * 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"); + if (copy_from_user(&dmi->data, (char __user *)user + minimum_data_size, + param_kernel->data_size - minimum_data_size)) goto bad; - } - +data_copied: /* Wipe the user buffer so we do not return it to userspace */ if (secure_data && clear_user(user, param_kernel->data_size)) goto bad; |