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Fri, 05 Jun 2026 08:42:54 -0700 (PDT) From: Samuel Moelius To: Gerd Hoffmann Cc: Samuel Moelius , Vivek Kasireddy , Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , dri-devel@lists.freedesktop.org (open list:USERSPACE DMA BUFFER DRIVER), linux-media@vger.kernel.org (open list:DMA BUFFER SHARING FRAMEWORK), linaro-mm-sig@lists.linaro.org (moderated list:DMA BUFFER SHARING FRAMEWORK), linux-kernel@vger.kernel.org (open list) Subject: [PATCH] dma-buf: udmabuf: validate create-list count before copying Date: Fri, 5 Jun 2026 15:42:51 +0000 Message-ID: <20260605154252.2125942-1-sam.moelius@trailofbits.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" UDMABUF_CREATE_LIST copies a variable-length list using a byte count derived from head.count. The list_limit module parameter is signed and writable, so setting it negative lets a large unsigned count bypass the limit check. The u32 byte-count calculation can then wrap, causing only a small list to be copied while udmabuf_create() still iterates over the large count. Reject negative list_limit values and use checked size_t multiplication before copying the list. Assisted-by: Codex:gpt-5.5-cyber-preview Signed-off-by: Samuel Moelius --- drivers/dma-buf/udmabuf.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index 94b8ecb892bb..46b077639bfb 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include =20 @@ -489,13 +490,14 @@ static long udmabuf_ioctl_create_list(struct file *fi= lp, unsigned long arg) struct udmabuf_create_list head; struct udmabuf_create_item *list; int ret =3D -EINVAL; - u32 lsize; + size_t lsize; =20 if (copy_from_user(&head, (void __user *)arg, sizeof(head))) return -EFAULT; - if (head.count > list_limit) + if (list_limit < 0 || head.count > list_limit) + return -EINVAL; + if (check_mul_overflow(sizeof(struct udmabuf_create_item), head.count, &l= size)) return -EINVAL; - lsize =3D sizeof(struct udmabuf_create_item) * head.count; list =3D memdup_user((void __user *)(arg + sizeof(head)), lsize); if (IS_ERR(list)) return PTR_ERR(list); --=20 2.43.0