From: Eric W. Biederman ebiederm@xmission.com
[ 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: 0ea820cf9bf5 ("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 --- arch/sh/kernel/cpu/fpu.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/sh/kernel/cpu/fpu.c b/arch/sh/kernel/cpu/fpu.c index ae354a2931e7e..fd6db0ab19288 100644 --- a/arch/sh/kernel/cpu/fpu.c +++ b/arch/sh/kernel/cpu/fpu.c @@ -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);