Re: [PATCH v2 1/4] copy_sighand: Handle architectures where sizeof(unsigned long) < sizeof(u64)
From: David Hildenbrand <hidden>
Date: 2025-09-01 13:25:04
Also in:
cgroups, linux-alpha, linux-arm-kernel, linux-block, linux-fsdevel, linux-m68k, linux-mips, linux-mm, linux-perf-users, linux-riscv, linux-s390, linux-security-module, linux-sh, linux-trace-kernel, linux-um, lkml, loongarch, netdev, selinux, sparclinux, stable
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 <redacted>
---(stripping To list) Acked-by: David Hildenbrand <redacted> -- Cheers David / dhildenb