[PATCH 5.4 084/156] riscv: Fixup race condition on PG_dcache_clean in flush_icache_pte

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From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>

commit 950b879b7f0251317d26bae0687e72592d607532 upstream.

In commit 588a513d3425 ("arm64: Fix race condition on PG_dcache_clean
in __sync_icache_dcache()"), we found RISC-V has the same issue as the
previous arm64. The previous implementation didn't guarantee the correct
sequence of operations, which means flush_icache_all() hasn't been
called when the PG_dcache_clean was set. That would cause a risk of page
synchronization.

Fixes: 08f051eda33b ("RISC-V: Flush I$ when making a dirty page executable")
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230127035306.1819561-1-guoren@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/riscv/mm/cacheflush.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -71,6 +71,8 @@ void flush_icache_pte(pte_t pte)
 {
 	struct page *page = pte_page(pte);
 
-	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
+	if (!test_bit(PG_dcache_clean, &page->flags)) {
 		flush_icache_all();
+		set_bit(PG_dcache_clean, &page->flags);
+	}
 }





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