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riscv: fix livelock in uaccess

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riscv 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: Björn Töpel <bjorn@kernel.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2023-01-30 23:55:52 -05:00
parent bd75497a77
commit d835eb3a57
1 changed files with 4 additions and 1 deletions
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5
arch/riscv/mm/fault.c
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@ -324,8 +324,11 @@ good_area:
* signal first. We do not need to release the mmap_lock because it
* would already be released in __lock_page_or_retry in mm/filemap.c.
*/
if (fault_signal_pending(fault, regs))
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
no_context(regs, addr);
return;
}
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)