From 79c54c97c7735e09f9e2193a713f30e56eec00dc Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
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 <viro@zeniv.linux.org.uk>
---
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 91259f291c540..179295b14664a 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 4acc12eafbf54..d91305de694c5 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)
--
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