[PATCH AUTOSEL 5.7 16/28] s390/ptrace: return -ENOSYS when invalid syscall is supplied

Sasha Levin
2020-06-23T17:43:16Z

From: Sven Schnelle <svens@linux.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@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.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