Commit 9770f8c2 authored Oct 20, 2021 by Eric W. Biederman Committed by Greg Kroah-Hartman Nov 17, 2021

signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL)

[ Upstream commit ce0ee4e6ac99606f3945f4d47775544edc3f7985 ]

Today the sh code allocates memory the first time a process uses
the fpu.  If that memory allocation fails, kill the affected task
with force_sig(SIGKILL) rather than do_group_exit(SIGKILL).

Calling do_group_exit from an exception handler can potentially lead
to dead locks as do_group_exit is not designed to be called from
interrupt context.  Instead use force_sig(SIGKILL) to kill the
userspace process.  Sending signals in general and force_sig in
particular has been tested from interrupt context so there should be
no problems.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: linux-sh@vger.kernel.org
Fixes: 0ea820cf ("sh: Move over to dynamically allocated FPU context.")
Link: https://lkml.kernel.org/r/20211020174406.17889-6-ebiederm@xmission.com


Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 9e698519

arch/sh/kernel/cpu/fpu.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -62,18 +62,20 @@ void fpu_state_restore(struct pt_regs *regs)
		}

		if (!tsk_used_math(tsk)) {
		local_irq_enable();
		int ret;
		/*
		* does a slab alloc which can sleep
		*/
		if (init_fpu(tsk)) {
		local_irq_enable();
		ret = init_fpu(tsk);
		local_irq_disable();
		if (ret) {
		/*
		* ran out of memory!
		*/
		do_group_exit(SIGKILL);
		force_sig(SIGKILL);
		return;
		}
		local_irq_disable();
		}

		grab_fpu(regs);