Re: [PATCH v7 2/7] rust: uaccess: add write_dma() for copying from DMA buffers to userspace

[kernel test robot <lkp@intel.com>]

Hi Timur,

kernel test robot noticed the following build errors:

[auto build test ERROR on cea7b66a80412e2a5b74627b89ae25f1d0110a4b]

url:    https://github.com/intel-lab-lkp/linux/commits/Timur-Tabi/rust-device-add-device-name-method/20260204-065057
base:   cea7b66a80412e2a5b74627b89ae25f1d0110a4b
patch link:    https://lore.kernel.org/r/20260203224757.871729-3-ttabi%40nvidia.com
patch subject: [PATCH v7 2/7] rust: uaccess: add write_dma() for copying from DMA buffers to userspace
config: x86_64-rhel-9.4-rust (https://download.01.org/0day-ci/archive/20260204/202602040350.sw6i2Sp2-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260204/202602040350.sw6i2Sp2-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602040350.sw6i2Sp2-lkp@intel.com/

All errors (new ones prefixed by >>):

   PATH=/opt/cross/clang-20/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
   INFO PATH=/opt/cross/rustc-1.88.0-bindgen-0.72.1/cargo/bin:/opt/cross/clang-20/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
   /usr/bin/timeout -k 100 12h /usr/bin/make KCFLAGS= -fno-crash-diagnostics -Wno-error=return-type -Wreturn-type -funsigned-char -Wundef -falign-functions=64 W=1 --keep-going LLVM=1 -j32 -C source O=/kbuild/obj/consumer/x86_64-rhel-9.4-rust ARCH=x86_64 SHELL=/bin/bash rustfmtcheck
   make: Entering directory '/kbuild/src/consumer'
   make[1]: Entering directory '/kbuild/obj/consumer/x86_64-rhel-9.4-rust'
>> Diff in rust/kernel/uaccess.rs:471:
            // - `ptr` is valid for reading `len` bytes as required by this function's safety contract.
            // - `copy_to_user` validates the userspace address at runtime and returns non-zero on
            //   failure (e.g., bad address or unmapped memory).
   -        let res = unsafe {
   -            bindings::copy_to_user(self.ptr.as_mut_ptr(), ptr.cast::<c_void>(), len)
   -        };
   +        let res =
   +            unsafe { bindings::copy_to_user(self.ptr.as_mut_ptr(), ptr.cast::<c_void>(), len) };
            if res != 0 {
                return Err(EFAULT);
            }
>> Diff in rust/kernel/uaccess.rs:471:
            // - `ptr` is valid for reading `len` bytes as required by this function's safety contract.
            // - `copy_to_user` validates the userspace address at runtime and returns non-zero on
            //   failure (e.g., bad address or unmapped memory).
   -        let res = unsafe {
   -            bindings::copy_to_user(self.ptr.as_mut_ptr(), ptr.cast::<c_void>(), len)
   -        };
   +        let res =
   +            unsafe { bindings::copy_to_user(self.ptr.as_mut_ptr(), ptr.cast::<c_void>(), len) };
            if res != 0 {
                return Err(EFAULT);
            }
   make[1]: Leaving directory '/kbuild/obj/consumer/x86_64-rhel-9.4-rust'
   make[2]: *** [Makefile:1871: rustfmt] Error 123
   make[2]: Target 'rustfmtcheck' not remade because of errors.
   make[1]: *** [Makefile:248: __sub-make] Error 2
   make: *** [Makefile:248: __sub-make] Error 2
   make[1]: Target 'rustfmtcheck' not remade because of errors.
   make: Target 'rustfmtcheck' not remade because of errors.
   make: Leaving directory '/kbuild/src/consumer'

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