[PATCH 1/3] usb: usbip: fix integer overflow in usbip_recv_iso()

[PATCH 1/3] usb: usbip: fix integer overflow in usbip_recv_iso()

[Kelvin Mbogo]

usbip_recv_iso() computes the iso descriptor buffer size as:

    int size = np * sizeof(*iso);

where np comes straight from the wire (urb->number_of_packets, set by
usbip_pack_ret_submit() before we get here).  With np = 0x10000001 and
sizeof(*iso) == 16 the product is 0x100000010 which truncates to 16 on
a 32-bit int.  kzalloc(16) succeeds but the following receive loop
writes np * 16 bytes into it - game over.

USBIP_MAX_ISO_PACKETS (1024) already exists in usbip_common.h for the
submit path but was never enforced on the receive side.

Clamp np to [1, USBIP_MAX_ISO_PACKETS] and switch to kmalloc_array()
so the allocator itself can catch overflows in the future.

One subtlety: usbip_pack_ret_submit() already copied the bogus np into
urb->number_of_packets before we run, so just returning -EPROTO isn't
enough - processcompl() in the HCD will still iterate that many
iso_frame_desc entries when it completes the failed URB.  Zero out
urb->number_of_packets before bailing to prevent that secondary crash
(confirmed on 6.12.0, processcompl+0x63 with CR2 in unmapped slab).

Reported-by: Kelvin Mbogo <addcontent08@gmail.com>
Signed-off-by: Kelvin Mbogo <addcontent08@gmail.com>
---
 drivers/usb/usbip/usbip_common.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
index a2b2da1..549e34b 100644
--- a/drivers/usb/usbip/usbip_common.c
+++ b/drivers/usb/usbip/usbip_common.c
@@ -662,7 +662,6 @@ int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
 	void *buff;
 	struct usbip_iso_packet_descriptor *iso;
 	int np = urb->number_of_packets;
-	int size = np * sizeof(*iso);
 	int i;
 	int ret;
 	int total_length = 0;
@@ -674,12 +673,22 @@ int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
 	if (np == 0)
 		return 0;
 
-	buff = kzalloc(size, GFP_KERNEL);
+	if (np < 0 || np > USBIP_MAX_ISO_PACKETS) {
+		dev_err(&urb->dev->dev,
+			"recv iso: invalid number_of_packets %d\n", np);
+		/* usbip_pack_ret_submit() already set urb->number_of_packets
+		 * from the wire - zero it so processcompl() does not iterate
+		 * OOB descriptors on the way out. */
+		urb->number_of_packets = 0;
+		return -EPROTO;
+	}
+
+	buff = kmalloc_array(np, sizeof(*iso), GFP_KERNEL);
 	if (!buff)
 		return -ENOMEM;
 
-	ret = usbip_recv(ud->tcp_socket, buff, size);
-	if (ret != size) {
+	ret = usbip_recv(ud->tcp_socket, buff, np * sizeof(*iso));
+	if (ret != np * (int)sizeof(*iso)) {
 		dev_err(&urb->dev->dev, "recv iso_frame_descriptor, %d\n",
 			ret);
 		kfree(buff);
-- 
2.34.1

[PATCH 2/3] usb: usbip: validate iso frame actual_length in usbip_recv_iso()

[Kelvin Mbogo]

usbip_recv_iso() sums each frame's actual_length into an int
accumulator without checking the individual values first:

    total_length += urb->iso_frame_desc[i].actual_length;

A malicious server can send actual_length = 0xFFFFFFFC for one frame
and a small value for the other, making the signed sum wrap around to
match urb->actual_length.  The sanity check passes, and usbip_pad_iso()
later computes a negative actualoffset, feeding it to memmove() as a
source pointer - reads before the allocation, leaked to userspace via
USBDEVFS_REAPURB.

Reject any frame whose actual_length exceeds transfer_buffer_length
(one frame can't carry more data than the whole buffer), and widen the
accumulator to u32 so that many moderately-large frames can't wrap it
either.

Reported-by: Kelvin Mbogo <addcontent08@gmail.com>
Signed-off-by: Kelvin Mbogo <addcontent08@gmail.com>
---
 drivers/usb/usbip/usbip_common.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
index 549e34b..c79a90f 100644
--- a/drivers/usb/usbip/usbip_common.c
+++ b/drivers/usb/usbip/usbip_common.c
@@ -664,7 +664,7 @@ int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
 	int np = urb->number_of_packets;
 	int i;
 	int ret;
-	int total_length = 0;
+	u32 total_length = 0;
 
 	if (!usb_pipeisoc(urb->pipe))
 		return 0;
@@ -705,14 +705,23 @@ int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
 	for (i = 0; i < np; i++) {
 		usbip_iso_packet_correct_endian(&iso[i], 0);
 		usbip_pack_iso(&iso[i], &urb->iso_frame_desc[i], 0);
+		if (urb->iso_frame_desc[i].actual_length >
+				(unsigned int)urb->transfer_buffer_length) {
+			dev_err(&urb->dev->dev,
+				"recv iso: frame actual_length %u exceeds buffer %d\n",
+				urb->iso_frame_desc[i].actual_length,
+				urb->transfer_buffer_length);
+			kfree(buff);
+			return -EPROTO;
+		}
 		total_length += urb->iso_frame_desc[i].actual_length;
 	}
 
 	kfree(buff);
 
-	if (total_length != urb->actual_length) {
+	if (total_length != (u32)urb->actual_length) {
 		dev_err(&urb->dev->dev,
-			"total length of iso packets %d not equal to actual length of buffer %d\n",
+			"total length of iso packets %u not equal to actual length of buffer %d\n",
 			total_length, urb->actual_length);
 
 		if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC)
-- 
2.34.1

[PATCH 3/3] usb: usbip: fix OOB read/write in usbip_pad_iso()

[Kelvin Mbogo]

usbip_pad_iso() repositions ISO frame data within the transfer buffer
via memmove().  Neither the source offset (actualoffset, derived by
subtracting wire-supplied actual_length values) nor the destination
offset (iso_frame_desc[i].offset, taken directly from the wire) is
bounds-checked.

If a crafted actual_length wraps actualoffset negative through the
subtraction (see patch 2/3 for the root cause), the memmove source
points before the allocation - slab OOB read, data returned to
userspace.

Independently, iso_frame_desc[i].offset is never validated against
transfer_buffer_length.  Setting offset past the end of the buffer
gives a fully controlled OOB write into whatever sits next in the
slab - confirmed with offset=400 on a 392-byte buffer, 64-byte write.

Add bounds checks for both the source and destination ranges before
each memmove call.  Use unsigned comparisons after the sign check on
actualoffset to avoid signed/unsigned conversion surprises.

Reported-by: Kelvin Mbogo <addcontent08@gmail.com>
Signed-off-by: Kelvin Mbogo <addcontent08@gmail.com>
---
 drivers/usb/usbip/usbip_common.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
index c79a90f..e95e63f 100644
--- a/drivers/usb/usbip/usbip_common.c
+++ b/drivers/usb/usbip/usbip_common.c
@@ -769,6 +769,36 @@ void usbip_pad_iso(struct usbip_device *ud, struct urb *urb)
 	 */
 	for (i = np-1; i > 0; i--) {
 		actualoffset -= urb->iso_frame_desc[i].actual_length;
+
+		/* source: actualoffset can go negative via crafted
+		 * actual_length - catch that plus any overshoot */
+		if (actualoffset < 0 ||
+		    (unsigned int)actualoffset > (unsigned int)urb->transfer_buffer_length ||
+		    urb->iso_frame_desc[i].actual_length >
+				(unsigned int)urb->transfer_buffer_length -
+				(unsigned int)actualoffset) {
+			dev_err(&urb->dev->dev,
+				"pad_iso: bad src off=%d len=%u bufsz=%d\n",
+				actualoffset,
+				urb->iso_frame_desc[i].actual_length,
+				urb->transfer_buffer_length);
+			return;
+		}
+
+		/* dest: offset comes straight from the wire, never checked */
+		if (urb->iso_frame_desc[i].offset >
+				(unsigned int)urb->transfer_buffer_length ||
+		    urb->iso_frame_desc[i].actual_length >
+				(unsigned int)urb->transfer_buffer_length -
+				urb->iso_frame_desc[i].offset) {
+			dev_err(&urb->dev->dev,
+				"pad_iso: bad dst off=%u len=%u bufsz=%d\n",
+				urb->iso_frame_desc[i].offset,
+				urb->iso_frame_desc[i].actual_length,
+				urb->transfer_buffer_length);
+			return;
+		}
+
 		memmove(urb->transfer_buffer + urb->iso_frame_desc[i].offset,
 			urb->transfer_buffer + actualoffset,
 			urb->iso_frame_desc[i].actual_length);
-- 
2.34.1

Re: [PATCH 1/3] usb: usbip: fix integer overflow in usbip_recv_iso()

[Greg KH]

On Wed, Mar 25, 2026 at 12:26:04PM +0300, Kelvin Mbogo wrote:
> usbip_recv_iso() computes the iso descriptor buffer size as:
> 
>     int size = np * sizeof(*iso);
> 
> where np comes straight from the wire (urb->number_of_packets, set by
> usbip_pack_ret_submit() before we get here).  With np = 0x10000001 and
> sizeof(*iso) == 16 the product is 0x100000010 which truncates to 16 on
> a 32-bit int.  kzalloc(16) succeeds but the following receive loop
> writes np * 16 bytes into it - game over.
> 
> USBIP_MAX_ISO_PACKETS (1024) already exists in usbip_common.h for the
> submit path but was never enforced on the receive side.
> 
> Clamp np to [1, USBIP_MAX_ISO_PACKETS] and switch to kmalloc_array()
> so the allocator itself can catch overflows in the future.
> 
> One subtlety: usbip_pack_ret_submit() already copied the bogus np into
> urb->number_of_packets before we run, so just returning -EPROTO isn't
> enough - processcompl() in the HCD will still iterate that many
> iso_frame_desc entries when it completes the failed URB.  Zero out
> urb->number_of_packets before bailing to prevent that secondary crash
> (confirmed on 6.12.0, processcompl+0x63 with CR2 in unmapped slab).
> 
> Reported-by: Kelvin Mbogo <addcontent08@gmail.com>
> Signed-off-by: Kelvin Mbogo <addcontent08@gmail.com>

Nit, no need to have reported-by when you author and sign off on a
patch.

and as this is public, no need to cc: security@k.o anymore either.

> ---
>  drivers/usb/usbip/usbip_common.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
> index a2b2da1..549e34b 100644
> --- a/drivers/usb/usbip/usbip_common.c
> +++ b/drivers/usb/usbip/usbip_common.c
> @@ -662,7 +662,6 @@ int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
>  	void *buff;
>  	struct usbip_iso_packet_descriptor *iso;
>  	int np = urb->number_of_packets;
> -	int size = np * sizeof(*iso);
>  	int i;
>  	int ret;
>  	int total_length = 0;
> @@ -674,12 +673,22 @@ int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
>  	if (np == 0)
>  		return 0;
>  
> -	buff = kzalloc(size, GFP_KERNEL);
> +	if (np < 0 || np > USBIP_MAX_ISO_PACKETS) {
> +		dev_err(&urb->dev->dev,
> +			"recv iso: invalid number_of_packets %d\n", np);
> +		/* usbip_pack_ret_submit() already set urb->number_of_packets
> +		 * from the wire - zero it so processcompl() does not iterate
> +		 * OOB descriptors on the way out. */
> +		urb->number_of_packets = 0;
> +		return -EPROTO;
> +	}

Why not just make the np == 0 do the same here and just silently eat the
message?  Do we have to report an error?

Also, nit, the comment style you used here is for network drivers, not
USB drivers :)


> +
> +	buff = kmalloc_array(np, sizeof(*iso), GFP_KERNEL);

Not kzalloc_objs()?


>  	if (!buff)
>  		return -ENOMEM;
>  
> -	ret = usbip_recv(ud->tcp_socket, buff, size);
> -	if (ret != size) {
> +	ret = usbip_recv(ud->tcp_socket, buff, np * sizeof(*iso));
> +	if (ret != np * (int)sizeof(*iso)) {

is the cast needed?  Or is there a compiler warning without it?

And as you are calculating "np * sizeof(*iso)" multiple times here, why
not just keep the "size" variable at the top here?  Then that would be
one less line changed here.

thanks,

greg k-h

Re: [PATCH 3/3] usb: usbip: fix OOB read/write in usbip_pad_iso()

[Greg KH]

On Wed, Mar 25, 2026 at 12:26:06PM +0300, Kelvin Mbogo wrote:
> usbip_pad_iso() repositions ISO frame data within the transfer buffer
> via memmove().  Neither the source offset (actualoffset, derived by
> subtracting wire-supplied actual_length values) nor the destination
> offset (iso_frame_desc[i].offset, taken directly from the wire) is
> bounds-checked.
> 
> If a crafted actual_length wraps actualoffset negative through the
> subtraction (see patch 2/3 for the root cause), the memmove source
> points before the allocation - slab OOB read, data returned to
> userspace.
> 
> Independently, iso_frame_desc[i].offset is never validated against
> transfer_buffer_length.  Setting offset past the end of the buffer
> gives a fully controlled OOB write into whatever sits next in the
> slab - confirmed with offset=400 on a 392-byte buffer, 64-byte write.
> 
> Add bounds checks for both the source and destination ranges before
> each memmove call.  Use unsigned comparisons after the sign check on
> actualoffset to avoid signed/unsigned conversion surprises.
> 
> Reported-by: Kelvin Mbogo <addcontent08@gmail.com>
> Signed-off-by: Kelvin Mbogo <addcontent08@gmail.com>
> ---
>  drivers/usb/usbip/usbip_common.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
> index c79a90f..e95e63f 100644
> --- a/drivers/usb/usbip/usbip_common.c
> +++ b/drivers/usb/usbip/usbip_common.c
> @@ -769,6 +769,36 @@ void usbip_pad_iso(struct usbip_device *ud, struct urb *urb)
>  	 */
>  	for (i = np-1; i > 0; i--) {
>  		actualoffset -= urb->iso_frame_desc[i].actual_length;
> +
> +		/* source: actualoffset can go negative via crafted
> +		 * actual_length - catch that plus any overshoot */
> +		if (actualoffset < 0 ||
> +		    (unsigned int)actualoffset > (unsigned int)urb->transfer_buffer_length ||
> +		    urb->iso_frame_desc[i].actual_length >
> +				(unsigned int)urb->transfer_buffer_length -
> +				(unsigned int)actualoffset) {


That's soem rough indentation, didn't checkpatch complain about it?

> +			dev_err(&urb->dev->dev,
> +				"pad_iso: bad src off=%d len=%u bufsz=%d\n",
> +				actualoffset,
> +				urb->iso_frame_desc[i].actual_length,
> +				urb->transfer_buffer_length);
> +			return;
> +		}
> +
> +		/* dest: offset comes straight from the wire, never checked */

as you are checking it here, why not say that?

> +		if (urb->iso_frame_desc[i].offset >
> +				(unsigned int)urb->transfer_buffer_length ||
> +		    urb->iso_frame_desc[i].actual_length >
> +				(unsigned int)urb->transfer_buffer_length -
> +				urb->iso_frame_desc[i].offset) {

Again, odd indentation.

thanks,

greg k-h