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authorWenwen Wang <wang6495@umn.edu>2018-05-08 08:50:28 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-07-03 11:27:12 +0200
commita61b352a7c23191108ae0c747a170f6bce5b154a (patch)
parentc91aad666676e5e5055a5427815a18f0d3fa6661 (diff)
virt: vbox: Only copy_from_user the request-header once
commit bd23a7269834dc7c1f93e83535d16ebc44b75eba upstream. In vbg_misc_device_ioctl(), the header of the ioctl argument is copied from the userspace pointer 'arg' and saved to the kernel object 'hdr'. Then the 'version', 'size_in', and 'size_out' fields of 'hdr' are verified. Before this commit, after the checks a buffer for the entire request would be allocated and then all data including the verified header would be copied from the userspace 'arg' pointer again. Given that the 'arg' pointer resides in userspace, a malicious userspace process can race to change the data pointed to by 'arg' between the two copies. By doing so, the user can bypass the verifications on the ioctl argument. This commit fixes this by using the already checked copy of the header to fill the header part of the allocated buffer and only copying the remainder of the data from userspace. Signed-off-by: Wenwen Wang <wang6495@umn.edu> Reviewed-by: Hans de Goede <hdegoede@redhat.com> Cc: Justin Forbes <jmforbes@linuxtx.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/virt/vboxguest/vboxguest_linux.c b/drivers/virt/vboxguest/vboxguest_linux.c
index 398d22693234..6e2a9619192d 100644
--- a/drivers/virt/vboxguest/vboxguest_linux.c
+++ b/drivers/virt/vboxguest/vboxguest_linux.c
@@ -121,7 +121,9 @@ static long vbg_misc_device_ioctl(struct file *filp, unsigned int req,
if (!buf)
return -ENOMEM;
- if (copy_from_user(buf, (void *)arg, hdr.size_in)) {
+ *((struct vbg_ioctl_hdr *)buf) = hdr;
+ if (copy_from_user(buf + sizeof(hdr), (void *)arg + sizeof(hdr),
+ hdr.size_in - sizeof(hdr))) {
ret = -EFAULT;
goto out;