From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Date: Tue, 28 Feb 2023 15:22:36 +0000 Subject: Re: [PATCH 08/10] parisc: fix livelock in uaccess Message-Id: <20230228152236.GA4088022@roeck-us.net> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Al Viro Cc: linux-arch@vger.kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org, Michal Simek , Dinh Nguyen , openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, sparclinux@vger.kernel.org, Linus Torvalds On Tue, Jan 31, 2023 at 08:06:27PM +0000, Al Viro wrote: > parisc equivalent of 26178ec11ef3 "x86: mm: consolidate VM_FAULT_RETRY handling" > If e.g. get_user() triggers a page fault and a fatal signal is caught, we might > end up with handle_mm_fault() returning VM_FAULT_RETRY and not doing anything > to page tables. In such case we must *not* return to the faulting insn - > that would repeat the entire thing without making any progress; what we need > instead is to treat that as failed (user) memory access. > > Signed-off-by: Al Viro > --- > arch/parisc/mm/fault.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c > index 869204e97ec9..bb30ff6a3e19 100644 > --- a/arch/parisc/mm/fault.c > +++ b/arch/parisc/mm/fault.c > @@ -308,8 +308,11 @@ void do_page_fault(struct pt_regs *regs, unsigned long code, > > fault = handle_mm_fault(vma, address, flags, regs); > > - if (fault_signal_pending(fault, regs)) > + if (fault_signal_pending(fault, regs)) { > + if (!user_mode(regs)) > + goto no_context; 0-day rightfully complains that this leaves 'msg' uninitialized. arch/parisc/mm/fault.c:427 do_page_fault() error: uninitialized symbol 'msg' Guenter > return; > + } > > /* The fault is fully completed (including releasing mmap lock) */ > if (fault & VM_FAULT_COMPLETED)