From d835eb3a57de50d16dd4a6b53f95dbc2bfa8ef48 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 30 Jan 2023 23:55:52 -0500 Subject: [PATCH] riscv: fix livelock in uaccess MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit riscv 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. Tested-by: Björn Töpel Tested-by: Geert Uytterhoeven Signed-off-by: Al Viro --- arch/riscv/mm/fault.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c index d86f7ce..c91d853 100644 --- a/arch/riscv/mm/fault.c +++ b/arch/riscv/mm/fault.c @@ -324,8 +324,11 @@ good_area: * signal first. We do not need to release the mmap_lock because it * would already be released in __lock_page_or_retry in mm/filemap.c. */ - if (fault_signal_pending(fault, regs)) + if (fault_signal_pending(fault, regs)) { + if (!user_mode(regs)) + no_context(regs, addr); return; + } /* The fault is fully completed (including releasing mmap lock) */ if (fault & VM_FAULT_COMPLETED) -- 2.7.4