From: Christophe Leroy christophe.leroy@c-s.fr
commit 415480dce2ef03bb8335deebd2f402f475443ce0 upstream.
If a page is already mapped RW without the DIRTY flag, the DIRTY flag is never set and a TLB store miss exception is taken forever.
This is easily reproduced with the following app:
void main(void) { volatile char *ptr = mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
*ptr = *ptr; }
When DIRTY flag is not set, bail out of TLB miss handler and take a minor page fault which will set the DIRTY flag.
Fixes: f8b58c64eaef ("powerpc/603: let's handle PAGE_DIRTY directly") Cc: stable@vger.kernel.org # v5.1+ Reported-by: Doug Crawford doug.crawford@intelight-its.com Signed-off-by: Christophe Leroy christophe.leroy@c-s.fr Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/80432f71194d7ee75b2f5043ecf1501cf1cca1f3.156619664... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kernel/head_32.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/powerpc/kernel/head_32.S +++ b/arch/powerpc/kernel/head_32.S @@ -557,9 +557,9 @@ DataStoreTLBMiss: cmplw 0,r1,r3 mfspr r2, SPRN_SPRG_PGDIR #ifdef CONFIG_SWAP - li r1, _PAGE_RW | _PAGE_PRESENT | _PAGE_ACCESSED + li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED #else - li r1, _PAGE_RW | _PAGE_PRESENT + li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT #endif bge- 112f lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */