From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: [PATCH 1/9] signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL) Date: Thu, 24 Jun 2021 13:59:04 -0500 Message-ID: <87zgvf6qdj.fsf_-_@disp2133> References: <87sg1lwhvm.fsf@disp2133> <6e47eff8-d0a4-8390-1222-e975bfbf3a65@gmail.com> <924ec53c-2fd9-2e1c-bbb1-3fda49809be4@gmail.com> <87eed4v2dc.fsf@disp2133> <5929e116-fa61-b211-342a-c706dcb834ca@gmail.com> <87fsxjorgs.fsf@disp2133> <87a6njf0ia.fsf@disp2133> <87tulpbp19.fsf@disp2133> <87zgvgabw1.fsf@disp2133> <875yy3850g.fsf_-_@disp2133> Mime-Version: 1.0 Return-path: In-Reply-To: <875yy3850g.fsf_-_@disp2133> (Eric W. Biederman's message of "Thu, 24 Jun 2021 13:57:35 -0500") List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Linus Torvalds Cc: Al Viro , Michael Schmitz , linux-arch , Jens Axboe , Oleg Nesterov , Linux Kernel Mailing List , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , Geert Uytterhoeven , linux-m68k , Arnd Bergmann , Ley Foon Tan , Tejun Heo , Kees Cook 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" --- 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