From: Nathan Chancellor nathan@kernel.org
[ Upstream commit 1413708f990cb7d025affd706ba9c23e2bfc1a27 ]
When building with CONFIG_FORTIFY_SOURCE=y and W=1, there is a warning because of the memcpy() in syscall_get_arguments():
In file included from include/linux/string.h:392, from include/linux/bitmap.h:13, from include/linux/cpumask.h:12, from arch/riscv/include/asm/processor.h:55, from include/linux/sched.h:13, from kernel/ptrace.c:13: In function 'fortify_memcpy_chk', inlined from 'syscall_get_arguments.isra' at arch/riscv/include/asm/syscall.h:66:2: include/linux/fortify-string.h:580:25: error: call to '__read_overflow2_field' declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning] 580 | __read_overflow2_field(q_size_field, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors
The fortified memcpy() routine enforces that the source is not overread and the destination is not overwritten if the size of either field and the size of the copy are known at compile time. The memcpy() in syscall_get_arguments() intentionally overreads from a1 to a5 in 'struct pt_regs' but this is bigger than the size of a1.
Normally, this could be solved by wrapping a1 through a5 with struct_group() but there was already a struct_group() applied to these members in commit bba547810c66 ("riscv: tracing: Fix __write_overflow_field in ftrace_partial_regs()").
Just avoid memcpy() altogether and write the copying of args from regs manually, which clears up the warning at the expense of three extra lines of code.
Signed-off-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Alexandre Ghiti alexghiti@rivosinc.com Reviewed-by: Dmitry V. Levin ldv@strace.io Link: https://lore.kernel.org/r/20250409-riscv-avoid-fortify-warning-syscall_get_a... Signed-off-by: Alexandre Ghiti alexghiti@rivosinc.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/include/asm/syscall.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h index 49350c8bd7b09..9fa0729bc6696 100644 --- a/arch/riscv/include/asm/syscall.h +++ b/arch/riscv/include/asm/syscall.h @@ -60,8 +60,11 @@ static inline void syscall_get_arguments(struct task_struct *task, unsigned long *args) { args[0] = regs->orig_a0; - args++; - memcpy(args, ®s->a1, 5 * sizeof(args[0])); + args[1] = regs->a1; + args[2] = regs->a2; + args[3] = regs->a3; + args[4] = regs->a4; + args[5] = regs->a5; }
static inline void syscall_set_arguments(struct task_struct *task,