From 79c54c97c7735e09f9e2193a713f30e56eec00dc Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 31 Jan 2023 00:03:40 -0500 Subject: [PATCH] sparc: fix livelock in uaccess sparc 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/sparc/mm/fault_32.c | 5 ++++- arch/sparc/mm/fault_64.c | 7 ++++++- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/sparc/mm/fault_32.c b/arch/sparc/mm/fault_32.c index 91259f291c54..179295b14664 100644 --- a/arch/sparc/mm/fault_32.c +++ b/arch/sparc/mm/fault_32.c @@ -187,8 +187,11 @@ asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write, */ fault = handle_mm_fault(vma, address, flags, regs); - if (fault_signal_pending(fault, regs)) + if (fault_signal_pending(fault, regs)) { + if (!from_user) + goto no_context; return; + } /* The fault is fully completed (including releasing mmap lock) */ if (fault & VM_FAULT_COMPLETED) diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c index 4acc12eafbf5..d91305de694c 100644 --- a/arch/sparc/mm/fault_64.c +++ b/arch/sparc/mm/fault_64.c @@ -424,8 +424,13 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs) fault = handle_mm_fault(vma, address, flags, regs); - if (fault_signal_pending(fault, regs)) + if (fault_signal_pending(fault, regs)) { + if (regs->tstate & TSTATE_PRIV) { + insn = get_fault_insn(regs, insn); + goto handle_kernel_fault; + } goto exit_exception; + } /* The fault is fully completed (including releasing mmap lock) */ if (fault & VM_FAULT_COMPLETED)