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Tsirkin" , Gabriel Somlo Cc: qemu-devel@nongnu.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Yousef Alhouseen Subject: [PATCH] firmware: qemu_fw_cfg: reject overflowing file directories Date: Sun, 28 Jun 2026 01:54:28 +0200 Message-ID: <20260627235428.16263-1-alhouseenyousef@gmail.com> X-Mailer: git-send-email 2.54.0 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" The fw_cfg file count is supplied by the VMM. On 32-bit systems, multiplying a large count by the directory entry size can wrap, resulting in a short allocation and an out-of-bounds walk of the directory. Reject counts whose directory size cannot be represented by size_t before allocating or reading the directory. Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg de= vice") Cc: stable@vger.kernel.org Signed-off-by: Yousef Alhouseen --- drivers/firmware/qemu_fw_cfg.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c index 0c51a9df5..3d5eece35 100644 --- a/drivers/firmware/qemu_fw_cfg.c +++ b/drivers/firmware/qemu_fw_cfg.c @@ -34,6 +34,7 @@ #include #include #include +#include #include #include #include @@ -642,7 +643,8 @@ static int fw_cfg_register_dir_entries(void) return ret; =20 count =3D be32_to_cpu(files_count); - dir_size =3D count * sizeof(struct fw_cfg_file); + if (check_mul_overflow((size_t)count, sizeof(*dir), &dir_size)) + return -EOVERFLOW; =20 dir =3D kmalloc(dir_size, GFP_KERNEL); if (!dir) --=20 2.54.0