linux-kernel - [PATCH] riscv: reject invalid syscalls below -1

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Message-Id: <20191218084757.904971-1-david.abdurachmanov@sifive.com>
Date:   Wed, 18 Dec 2019 10:47:56 +0200
From:   David Abdurachmanov <david.abdurachmanov@...il.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        David Abdurachmanov <david.abdurachmanov@...ive.com>,
        Kees Cook <keescook@...omium.org>,
        Anup Patel <Anup.Patel@....com>,
        Vincent Chen <vincent.chen@...ive.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Bin Meng <bmeng.cn@...il.com>, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     david.abdurachmanov@...il.com
Subject: [PATCH] riscv: reject invalid syscalls below -1

Running "stress-ng --enosys 4 -t 20 -v" showed a large number of kernel oops
with "Unable to handle kernel paging request at virtual address" message. This
happens when enosys stressor starts testing random non-valid syscalls.

I forgot to redirect any syscall below -1 to sys_ni_syscall.

With the patch kernel oops messages are gone while running stress-ng enosys
stressor.

Signed-off-by: David Abdurachmanov <david.abdurachmanov@...ive.com>
Fixes: 5340627e3fe0 ("riscv: add support for SECCOMP and SECCOMP_FILTER")
---
 arch/riscv/kernel/entry.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index a1349ca64669..e163b7b64c86 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -246,6 +246,7 @@ check_syscall_nr:
 	 */
 	li t1, -1
 	beq a7, t1, ret_from_syscall_rejected
+	blt a7, t1, 1f
 	/* Call syscall */
 	la s0, sys_call_table
 	slli t0, a7, RISCV_LGPTR
-- 
2.24.1