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misc: mic: fix possible signed underflow (undefined behavior) in userspace API

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iovcnt is declared as a signed integer in both the userspace API and
as a local variable in mic_virtio.c. The while() loop in mic_virtio.c
iterates until the local variable iovcnt reaches the value 0. If
userspace passes e.g. INT_MIN as iovcnt field, this loop then appears
to depend on an undefined behavior (signed underflow) to complete.
The fix is to use unsigned integers in both the userspace API and
the local variable.

This issue was reported @ https://lkml.org/lkml/2014/1/10/10

Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Sudeep Dutt <sudeep.dutt@intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sudeep Dutt 2014-02-03 14:53:19 -08:00 committed by Greg Kroah-Hartman
parent 01ab1167cd
commit 3b1cc9b962
2 changed files with 3 additions and 2 deletions
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3
drivers/misc/mic/host/mic_virtio.c
View File

@ -156,7 +156,8 @@ static int mic_vringh_copy(struct mic_vdev *mvdev, struct vringh_kiov *iov,
static int _mic_virtio_copy(struct mic_vdev *mvdev,
struct mic_copy_desc *copy)
{
int ret = 0, iovcnt = copy->iovcnt;
int ret = 0;
u32 iovcnt = copy->iovcnt;
struct iovec iov;
struct iovec __user *u_iov = copy->iov;
void __user *ubuf = NULL;

2
include/uapi/linux/mic_ioctl.h
View File

@ -39,7 +39,7 @@ struct mic_copy_desc {
#else
struct iovec *iov;
#endif
int iovcnt;
__u32 iovcnt;
__u8 vr_idx;
__u8 update_used;
__u32 out_len;