io_uring: fix compat for IORING_REGISTER_FILES_UPDATE

fds field of struct io_uring_files_update is problematic with regards
to compat user space, as pointer size is different in 32-bit, 32-on-64-bit,
and 64-bit user space.  In order to avoid custom handling of compat in
the syscall implementation, make fds __u64 and use u64_to_user_ptr in
order to retrieve it.  Also, align the field naturally and check that
no garbage is passed there.

Fixes: c3a31e605620c279 ("io_uring: add support for IORING_REGISTER_FILES_UPDATE")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 187dd94..5953d7f 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4463,13 +4463,15 @@ static int io_sqe_files_update(struct io_ring_ctx *ctx, void __user *arg,
                return -EINVAL;
        if (copy_from_user(&up, arg, sizeof(up)))
                return -EFAULT;
+       if (up.resv)
+               return -EINVAL;
        if (check_add_overflow(up.offset, nr_args, &done))
                return -EOVERFLOW;
        if (done > ctx->nr_user_files)
                return -EINVAL;
 
        done = 0;
-       fds = (__s32 __user *) up.fds;
+       fds = u64_to_user_ptr(up.fds);
        while (nr_args) {
                struct fixed_file_table *table;
                unsigned index;

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index a3300e1..55cfcb7 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -178,7 +178,8 @@ struct io_uring_params {
 
 struct io_uring_files_update {
        __u32 offset;
-       __s32 *fds;
+       __u32 resv;
+       __aligned_u64 /* __s32 * */ fds;
 };
 
 #endif