linux-kernel - [PATCH 4.14 16/71] ARM: net: bpf: fix stack alignment

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Date:   Mon, 29 Jan 2018 13:56:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Russell King <rmk+kernel@...linux.org.uk>
Subject: [PATCH 4.14 16/71] ARM: net: bpf: fix stack alignment

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Russell King <rmk+kernel@...linux.org.uk>

commit d1220efd23484c72c82d5471f05daeb35b5d1916 upstream.

As per 2dede2d8e925 ("ARM EABI: stack pointer must be 64-bit aligned
after a CPU exception") the stack should be aligned to a 64-bit boundary
on EABI systems.  Ensure that the eBPF JIT appropraitely aligns the
stack.

Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler")
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/net/bpf_jit_32.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -179,8 +179,13 @@ static void jit_fill_hole(void *area, un
 		*ptr++ = __opcode_to_mem_arm(ARM_INST_UDF);
 }
 
-/* Stack must be multiples of 16 Bytes */
-#define STACK_ALIGN(sz) (((sz) + 3) & ~3)
+#if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5)
+/* EABI requires the stack to be aligned to 64-bit boundaries */
+#define STACK_ALIGNMENT	8
+#else
+/* Stack must be aligned to 32-bit boundaries */
+#define STACK_ALIGNMENT	4
+#endif
 
 /* Stack space for BPF_REG_2, BPF_REG_3, BPF_REG_4,
  * BPF_REG_5, BPF_REG_7, BPF_REG_8, BPF_REG_9,
@@ -194,7 +199,7 @@ static void jit_fill_hole(void *area, un
 	 + SCRATCH_SIZE + \
 	 + 4 /* extra for skb_copy_bits buffer */)
 
-#define STACK_SIZE STACK_ALIGN(_STACK_SIZE)
+#define STACK_SIZE ALIGN(_STACK_SIZE, STACK_ALIGNMENT)
 
 /* Get the offset of eBPF REGISTERs stored on scratch space. */
 #define STACK_VAR(off) (STACK_SIZE-off-4)