powerpc/kasan: Force thread size increase with KASAN

[ Upstream commit 3e8635fb2e072672cbc650989ffedf8300ad67fb ]

KASAN causes increased stack usage, which can lead to stack overflows.

The logic in Kconfig to suggest a larger default doesn't work if a user
has CONFIG_EXPERT enabled and has an existing .config with a smaller
value.

Follow the lead of x86 and arm64, and force the thread size to be
increased when KASAN is enabled.

That also has the effect of enlarging the stack for 64-bit KASAN builds,
which is also desirable.

Fixes: edbadaf06710 ("powerpc/kasan: Fix stack overflow by increasing THREAD_SHIFT")
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mpe: Use MIN_THREAD_SHIFT as suggested by Christophe]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220601143114.133524-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 174edabb74fa112d80c3993c76e461910ef21d16..efb03d8d1f8bff556b51817c0b9fbef9cf9a4f7d 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -771,7 +771,6 @@ config THREAD_SHIFT
        range 13 15
        default "15" if PPC_256K_PAGES
        default "14" if PPC64
-       default "14" if KASAN
        default "13"
        help
          Used to define the stack size. The default is almost always what you

diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 125328d1b98027e12c36c0ebd3f3dab17892cbc2..af58f1ed3952e09b067dc2ff3b87c021db95f434 100644 (file)
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -14,10 +14,16 @@
 
 #ifdef __KERNEL__
 
-#if defined(CONFIG_VMAP_STACK) && CONFIG_THREAD_SHIFT < PAGE_SHIFT
+#ifdef CONFIG_KASAN
+#define MIN_THREAD_SHIFT       (CONFIG_THREAD_SHIFT + 1)
+#else
+#define MIN_THREAD_SHIFT       CONFIG_THREAD_SHIFT
+#endif
+
+#if defined(CONFIG_VMAP_STACK) && MIN_THREAD_SHIFT < PAGE_SHIFT
 #define THREAD_SHIFT           PAGE_SHIFT
 #else
-#define THREAD_SHIFT           CONFIG_THREAD_SHIFT
+#define THREAD_SHIFT           MIN_THREAD_SHIFT
 #endif
 
 #define THREAD_SIZE            (1 << THREAD_SHIFT)