[PATCH 5.15 742/917] signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL)

Greg Kroah-Hartman
2021-11-16T00:45:18Z

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);
--
2.33.0