linux-kernel - [PATCH 5.7 195/265] s390/ptrace: return -ENOSYS when invalid syscall is supplied

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Date:   Mon, 29 Jun 2020 11:17:08 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Sven Schnelle <svens@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.7 195/265] s390/ptrace: return -ENOSYS when invalid syscall is supplied

From: Sven Schnelle <svens@...ux.ibm.com>

[ Upstream commit cd29fa798001075a554b978df3a64e6656c25794 ]

The current code returns the syscall number which an invalid
syscall number is supplied and tracing is enabled. This makes
the strace testsuite fail.

Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/kernel/ptrace.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 9eee345568890..3f29646313e82 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -838,6 +838,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 {
 	unsigned long mask = -1UL;
+	long ret = -1;
 
 	if (is_compat_task())
 		mask = 0xffffffff;
@@ -854,8 +855,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 		 * debugger stored an invalid system call number. Skip
 		 * the system call and the system call restart handling.
 		 */
-		clear_pt_regs_flag(regs, PIF_SYSCALL);
-		return -1;
+		goto skip;
 	}
 
 #ifdef CONFIG_SECCOMP
@@ -871,7 +871,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 			sd.arch = AUDIT_ARCH_S390X;
 		}
 
-		sd.nr = regs->gprs[2] & 0xffff;
+		sd.nr = regs->int_code & 0xffff;
 		sd.args[0] = regs->orig_gpr2 & mask;
 		sd.args[1] = regs->gprs[3] & mask;
 		sd.args[2] = regs->gprs[4] & mask;
@@ -880,19 +880,26 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 		sd.args[5] = regs->gprs[7] & mask;
 
 		if (__secure_computing(&sd) == -1)
-			return -1;
+			goto skip;
 	}
 #endif /* CONFIG_SECCOMP */
 
 	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
-		trace_sys_enter(regs, regs->gprs[2]);
+		trace_sys_enter(regs, regs->int_code & 0xffff);
 
 
-	audit_syscall_entry(regs->gprs[2], regs->orig_gpr2 & mask,
+	audit_syscall_entry(regs->int_code & 0xffff, regs->orig_gpr2 & mask,
 			    regs->gprs[3] &mask, regs->gprs[4] &mask,
 			    regs->gprs[5] &mask);
 
+	if ((signed long)regs->gprs[2] >= NR_syscalls) {
+		regs->gprs[2] = -ENOSYS;
+		ret = -ENOSYS;
+	}
 	return regs->gprs[2];
+skip:
+	clear_pt_regs_flag(regs, PIF_SYSCALL);
+	return ret;
 }
 
 asmlinkage void do_syscall_trace_exit(struct pt_regs *regs)
-- 
2.25.1