[PATCH 1/9] signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL)

Eric W. Biederman
2021-06-24T18:59:18Z

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 locking 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.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
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 ae354a2931e7..fd6db0ab1928 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);
--
2.20.1