From: Christophe Leroy christophe.leroy@csgroup.eu
[ Upstream commit d93f9e23744b7bf11a98b2ddb091d129482ae179 ]
At interrupt exit, kuap_kernel_restore() calls kuap_unlock() with the value contained in regs->kuap. However, when regs->kuap contains 0xffffffff it means that KUAP was not unlocked so calling kuap_unlock() is unrelevant and results in jeopardising the contents of kernel space segment registers.
So check that regs->kuap doesn't contain KUAP_NONE before calling kuap_unlock(). In the meantime it also means that if KUAP has not been correcly locked back at interrupt exit, it must be locked before continuing. This is done by checking the content of current->thread.kuap which was returned by kuap_get_and_assert_locked()
Fixes: 16132529cee5 ("powerpc/32s: Rework Kernel Userspace Access Protection") Reported-by: Stan Johnson userm57@yahoo.com Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/0d0c4d0f050a637052287c09ba521bad960a2790.163171513... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/include/asm/book3s/32/kup.h | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h index d4b145b279f6..9f38040f0641 100644 --- a/arch/powerpc/include/asm/book3s/32/kup.h +++ b/arch/powerpc/include/asm/book3s/32/kup.h @@ -136,6 +136,14 @@ static inline void kuap_kernel_restore(struct pt_regs *regs, unsigned long kuap) if (kuap_is_disabled()) return;
+ if (unlikely(kuap != KUAP_NONE)) { + current->thread.kuap = KUAP_NONE; + kuap_lock(kuap, false); + } + + if (likely(regs->kuap == KUAP_NONE)) + return; + current->thread.kuap = regs->kuap;
kuap_unlock(regs->kuap, false);