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parisc: fix livelock in uaccess 

parisc equivalent of 26178ec11e "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: Helge Deller <deller@gmx.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2023-01-30 23:53:52 -05:00
parent 0b92ed09cb
commit 15261678a8
1 changed files with 6 additions and 1 deletions
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7
arch/parisc/mm/fault.c
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@ -308,8 +308,13 @@ 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)) {
msg = "Page fault: fault signal on kernel memory";
goto no_context;
}
return;
}
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)