According to Documentation/driver-api/ioctl.rst, in order to support 32-bit user space running on a 64-bit kernel, each subsystem or driver that implements an ioctl callback handler must also implement the corresponding compat_ioctl handler. The compat_ptr_ioctl() helper can be used in place of a custom compat_ioctl file operation for drivers that only take arguments that are pointers to compatible data structures.
In case of NS_* ioctls only NS_GET_OWNER_UID accepts an argument, and this argument is a pointer to uid_t type, which is universally defined to __kernel_uid32_t. This change fixes compat strace --pidns-translation. Note: when backporting this patch to stable kernels, commit "compat_ioctl: add compat_ptr_ioctl()" is needed as well. Reported-by: Ákos Uzonyi <[email protected]> Fixes: 6786741dbf99 ("nsfs: add ioctl to get an owning user namespace for ns file descriptor") Cc: [email protected] # v4.9+ Signed-off-by: Dmitry V. Levin <[email protected]> --- fs/nsfs.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/nsfs.c b/fs/nsfs.c index 800c1d0eb0d0..a00236bffa2c 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -21,6 +21,7 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, static const struct file_operations ns_file_operations = { .llseek = no_llseek, .unlocked_ioctl = ns_ioctl, + .compat_ioctl = compat_ptr_ioctl, }; static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) -- ldv
