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m68k: fix livelock in uaccess

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m68k 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: Finn Thain <fthain@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2023-01-30 23:48:54 -05:00
parent c9c3395d5e
commit bd75497a77
1 changed files with 4 additions and 1 deletions
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5
arch/m68k/mm/fault.c
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@ -138,8 +138,11 @@ good_area:
fault = handle_mm_fault(vma, address, flags, regs);
pr_debug("handle_mm_fault returns %x\n", fault);
if (fault_signal_pending(fault, regs))
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
goto no_context;
return 0;
}
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)