From: Arnd Bergmann arnd@arndb.de

Commit df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") introduced a warning for the autofs_dev_ioctl structure:

In function 'check_name', inlined from 'validate_dev_ioctl' at fs/autofs/dev-ioctl.c:131:9, inlined from '_autofs_dev_ioctl' at fs/autofs/dev-ioctl.c:624:8: fs/autofs/dev-ioctl.c:33:14: error: 'strchr' reading 1 or more bytes from a region of size 0 [-Werror=stringop-overread] 33 | if (!strchr(name, '/')) | ^~~~~~~~~~~~~~~~~ In file included from include/linux/auto_dev-ioctl.h:10, from fs/autofs/autofs_i.h:10, from fs/autofs/dev-ioctl.c:14: include/uapi/linux/auto_dev-ioctl.h: In function '_autofs_dev_ioctl': include/uapi/linux/auto_dev-ioctl.h:112:14: note: source object 'path' of size 0 112 | char path[0]; | ^~~~

This is easily fixed by changing the gnu 0-length array into a c99 flexible array. Since this is a uapi structure, we have to be careful about possible regressions but this one should be fine as they are equivalent here. While it would break building with ancient gcc versions that predate c99, it helps building with --std=c99 and -Wpedantic builds in user space, as well as non-gnu compilers. This means we probably also want it fixed in stable kernels.

Cc: stable@vger.kernel.org Cc: Kees Cook keescook@chromium.org Cc: Gustavo A. R. Silva" gustavoars@kernel.org Signed-off-by: Arnd Bergmann arnd@arndb.de --- Documentation/filesystems/autofs-mount-control.rst | 2 +- Documentation/filesystems/autofs.rst | 2 +- include/uapi/linux/auto_dev-ioctl.h | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/autofs-mount-control.rst b/Documentation/filesystems/autofs-mount-control.rst index bf4b511cdbe8..b5a379d25c40 100644 --- a/Documentation/filesystems/autofs-mount-control.rst +++ b/Documentation/filesystems/autofs-mount-control.rst @@ -196,7 +196,7 @@ information and return operation results:: struct args_ismountpoint ismountpoint; };

- char path[0]; + char path[]; };

The ioctlfd field is a mount point file descriptor of an autofs mount diff --git a/Documentation/filesystems/autofs.rst b/Documentation/filesystems/autofs.rst index 4f490278d22f..3b6e38e646cd 100644 --- a/Documentation/filesystems/autofs.rst +++ b/Documentation/filesystems/autofs.rst @@ -467,7 +467,7 @@ Each ioctl is passed a pointer to an `autofs_dev_ioctl` structure:: struct args_ismountpoint ismountpoint; };

- char path[0]; + char path[]; };

For the **OPEN_MOUNT** and **IS_MOUNTPOINT** commands, the target diff --git a/include/uapi/linux/auto_dev-ioctl.h b/include/uapi/linux/auto_dev-ioctl.h index 62e625356dc8..08be539605fc 100644 --- a/include/uapi/linux/auto_dev-ioctl.h +++ b/include/uapi/linux/auto_dev-ioctl.h @@ -109,7 +109,7 @@ struct autofs_dev_ioctl { struct args_ismountpoint ismountpoint; };

- char path[0]; + char path[]; };

static inline void init_autofs_dev_ioctl(struct autofs_dev_ioctl *in)