riscv: Fix kernel stack size when KASAN is enabled

commit cfb10de18538e383dbc4f3ce7f477ce49287ff3d upstream.

We use Kconfig to select the kernel stack size, doubling the default
size if KASAN is enabled.

But that actually only works if KASAN is selected from the beginning,
meaning that if KASAN config is added later (for example using
menuconfig), CONFIG_THREAD_SIZE_ORDER won't be updated, keeping the
default size, which is not enough for KASAN as reported in [1].

So fix this by moving the logic to compute the right kernel stack into a
header.

Fixes: a7555f6b62e7 ("riscv: stack: Add config of thread stack size")
Reported-by: syzbot+ba9eac24453387a9d502@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000eb301906222aadc2@google.com/ [1]
Cc: stable@vger.kernel.org
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240917150328.59831-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 140ff98a6efff85af5ac1f54a0c89caf0fa079ca..7d521a318840297c6bd5ddf2db11d5fdd06ff755 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -715,8 +715,7 @@ config IRQ_STACKS
 config THREAD_SIZE_ORDER
        int "Kernel stack size (in power-of-two numbers of page size)" if VMAP_STACK && EXPERT
        range 0 4
-       default 1 if 32BIT && !KASAN
-       default 3 if 64BIT && KASAN
+       default 1 if 32BIT
        default 2
        help
          Specify the Pages of thread stack size (from 4KB to 64KB), which also

diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 5d473343634b9d3af3c1f1872da25e6e60f77162..eec9d4394f5ba3d66ce5d1445690276396f73285 100644 (file)
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -12,7 +12,12 @@
 #include <linux/const.h>
 
 /* thread information allocation */
-#define THREAD_SIZE_ORDER      CONFIG_THREAD_SIZE_ORDER
+#ifdef CONFIG_KASAN
+#define KASAN_STACK_ORDER      1
+#else
+#define KASAN_STACK_ORDER      0
+#endif
+#define THREAD_SIZE_ORDER      (CONFIG_THREAD_SIZE_ORDER + KASAN_STACK_ORDER)
 #define THREAD_SIZE            (PAGE_SIZE << THREAD_SIZE_ORDER)
 
 /*