Adding upstream version 6.9.8.upstream/6.9.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 7 insertions, 9 deletions

diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index ad198262b9..7230f6e20a 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -53,17 +53,15 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 	syscall_set_return_value(current, regs, 0, ret);
 
 	/*
-	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
-	 * but not enough for arm64 stack utilization comfort. To keep
-	 * reasonable stack head room, reduce the maximum offset to 9 bits.
+	 * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
+	 * bits. The actual entropy will be further reduced by the compiler
+	 * when applying stack alignment constraints: the AAPCS mandates a
+	 * 16-byte aligned SP at function boundaries, which will remove the
+	 * 4 low bits from any entropy chosen here.
 	 *
-	 * The actual entropy will be further reduced by the compiler when
-	 * applying stack alignment constraints: the AAPCS mandates a
-	 * 16-byte (i.e. 4-bit) aligned SP at function boundaries.
-	 *
-	 * The resulting 5 bits of entropy is seen in SP[8:4].
+	 * The resulting 6 bits of entropy is seen in SP[9:4].
 	 */
-	choose_random_kstack_offset(get_random_u16() & 0x1FF);
+	choose_random_kstack_offset(get_random_u16());
 }
 
 static inline bool has_syscall_work(unsigned long flags)