| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-36894: usb: gadget: f_fs: Fix race between aio_cancel() and AIO request complete |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| usb: gadget: f_fs: Fix race between aio_cancel() and AIO request complete |
| |
| FFS based applications can utilize the aio_cancel() callback to dequeue |
| pending USB requests submitted to the UDC. There is a scenario where the |
| FFS application issues an AIO cancel call, while the UDC is handling a |
| soft disconnect. For a DWC3 based implementation, the callstack looks |
| like the following: |
| |
| DWC3 Gadget FFS Application |
| dwc3_gadget_soft_disconnect() ... |
| --> dwc3_stop_active_transfers() |
| --> dwc3_gadget_giveback(-ESHUTDOWN) |
| --> ffs_epfile_async_io_complete() ffs_aio_cancel() |
| --> usb_ep_free_request() --> usb_ep_dequeue() |
| |
| There is currently no locking implemented between the AIO completion |
| handler and AIO cancel, so the issue occurs if the completion routine is |
| running in parallel to an AIO cancel call coming from the FFS application. |
| As the completion call frees the USB request (io_data->req) the FFS |
| application is also referencing it for the usb_ep_dequeue() call. This can |
| lead to accessing a stale/hanging pointer. |
| |
| commit b566d38857fc ("usb: gadget: f_fs: use io_data->status consistently") |
| relocated the usb_ep_free_request() into ffs_epfile_async_io_complete(). |
| However, in order to properly implement locking to mitigate this issue, the |
| spinlock can't be added to ffs_epfile_async_io_complete(), as |
| usb_ep_dequeue() (if successfully dequeuing a USB request) will call the |
| function driver's completion handler in the same context. Hence, leading |
| into a deadlock. |
| |
| Fix this issue by moving the usb_ep_free_request() back to |
| ffs_user_copy_worker(), and ensuring that it explicitly sets io_data->req |
| to NULL after freeing it within the ffs->eps_lock. This resolves the race |
| condition above, as the ffs_aio_cancel() routine will not continue |
| attempting to dequeue a request that has already been freed, or the |
| ffs_user_copy_work() not freeing the USB request until the AIO cancel is |
| done referencing it. |
| |
| This fix depends on |
| commit b566d38857fc ("usb: gadget: f_fs: use io_data->status |
| consistently") |
| |
| The Linux kernel CVE team has assigned CVE-2024-36894 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 4.19.317 with commit f71a53148ce34898fef099b75386a3a9f4449311 |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 5.4.279 with commit 9e72ef59cbe61cd1243857a6418ca92104275867 |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 5.10.221 with commit e500b1c4e29ad0bd1c1332a1eaea2913627a92dd |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 5.15.162 with commit 3613e5023f09b3308545e9d1acda86017ebd418a |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 6.1.95 with commit a0fdccb1c9e027e3195f947f61aa87d6d0d2ea14 |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 6.6.31 with commit 73c05ad46bb4fbbdb346004651576d1c8dbcffbb |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 6.8.10 with commit d7461830823242702f5d84084bcccb25159003f4 |
| Issue introduced in 3.15 with commit 2e4c7553cd6f9c68bb741582dcb614edcbeca70f and fixed in 6.9 with commit 24729b307eefcd7c476065cd7351c1a018082c19 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-36894 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| drivers/usb/gadget/function/f_fs.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/f71a53148ce34898fef099b75386a3a9f4449311 |
| https://git.kernel.org/stable/c/9e72ef59cbe61cd1243857a6418ca92104275867 |
| https://git.kernel.org/stable/c/e500b1c4e29ad0bd1c1332a1eaea2913627a92dd |
| https://git.kernel.org/stable/c/3613e5023f09b3308545e9d1acda86017ebd418a |
| https://git.kernel.org/stable/c/a0fdccb1c9e027e3195f947f61aa87d6d0d2ea14 |
| https://git.kernel.org/stable/c/73c05ad46bb4fbbdb346004651576d1c8dbcffbb |
| https://git.kernel.org/stable/c/d7461830823242702f5d84084bcccb25159003f4 |
| https://git.kernel.org/stable/c/24729b307eefcd7c476065cd7351c1a018082c19 |
