Commit d835eb3a authored by Al Viro's avatar Al Viro
Browse files

riscv: fix livelock in uaccess 



riscv equivalent of 26178ec1 "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: default avatarBjörn Töpel <bjorn@kernel.org>
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent bd75497a

arch/riscv/mm/fault.c

+4 −1
Original line number Diff line number Diff line
@@ -324,8 +324,11 @@ asmlinkage void do_page_fault(struct pt_regs *regs) 
	 * 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)