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alpha: fix livelock in uaccess

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alpha 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.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2023-01-30 23:34:16 -05:00
parent 15261678a8
commit dce45493af
1 changed files with 4 additions and 1 deletions
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5
arch/alpha/mm/fault.c
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@@ -152,8 +152,11 @@ retry:
the fault. */ the fault. */
fault = handle_mm_fault(vma, address, flags, regs); 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;
return; return;
}
/* The fault is fully completed (including releasing mmap lock) */ /* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED) if (fault & VM_FAULT_COMPLETED)