[PATCH 5/5] arm64: compat: Poison the compat sigpage

[Will Deacon]

Commit 9c698bff66ab ("ARM: ensure the signal page contains defined contents")
poisoned the unused portions of the signal page for 32-bit Arm.

Implement the same poisoning for the compat signal page on arm64 rather
than using __GFP_ZERO.

Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/kernel/vdso.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 16bf0b46fb70..159b72a646ab 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -318,17 +318,20 @@ static int aarch32_alloc_kuser_vdso_page(void)
 	return 0;
 }
 
+#define COMPAT_SIGPAGE_POISON_WORD	0xe7fddef1
 static int aarch32_alloc_sigpage(void)
 {
 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
-	unsigned long sigpage;
+	__le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
+	void *sigpage;
 
-	sigpage = get_zeroed_page(GFP_KERNEL);
+	sigpage = (void *)__get_free_page(GFP_KERNEL);
 	if (!sigpage)
 		return -ENOMEM;
 
-	memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
+	memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
+	memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
 	aarch32_sig_page = virt_to_page(sigpage);
 	return 0;
 }
-- 
2.31.0.rc2.261.g7f71774620-goog