Re: [PATCH v2 1/4] copy_sighand: Handle architectures where sizeof(unsigned long) < sizeof(u64)

David Hildenbrand
2025-09-01T13:25:04Z

On 01.09.25 15:09, Simon Schuster via B4 Relay wrote:
> From: Simon Schuster <schuster.simon@siemens-energy.com>
>
> With the introduction of clone3 in commit 7f192e3cd316 ("fork: add
> clone3") the effective bit width of clone_flags on all architectures was
> increased from 32-bit to 64-bit. However, the signature of the copy_*
> helper functions (e.g., copy_sighand) used by copy_process was not
> adapted.
>
> As such, they truncate the flags on any 32-bit architectures that
> supports clone3 (arc, arm, csky, m68k, microblaze, mips32, openrisc,
> parisc32, powerpc32, riscv32, x86-32 and xtensa).
>
> For copy_sighand with CLONE_CLEAR_SIGHAND being an actual u64
> constant, this triggers an observable bug in kernel selftest
> clone3_clear_sighand:
>
> if (clone_flags & CLONE_CLEAR_SIGHAND)
>
> in function copy_sighand within fork.c will always fail given:
>
> unsigned long /* == uint32_t */ clone_flags
> #define CLONE_CLEAR_SIGHAND 0x100000000ULL
>
> This commit fixes the bug by always passing clone_flags to copy_sighand
> via their declared u64 type, invariant of architecture-dependent integer
> sizes.
>
> Fixes: b612e5df4587 ("clone3: add CLONE_CLEAR_SIGHAND")
> Cc: stable@vger.kernel.org # linux-5.5+
> Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> ---

(stripping To list)

Acked-by: David Hildenbrand <david@redhat.com>

--
Cheers

David / dhildenb