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Subject[PATCH 5.4 01/20] s390/ptrace: return -ENOSYS when invalid syscall is supplied
Date
From: Sven Schnelle <svens@linux.ibm.com>

commit cd29fa798001075a554b978df3a64e6656c25794 upstream.

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>
Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1895132
[krzysztof: adjusted the backport around missing ifdef CONFIG_SECCOMP,
add Link and Fixes; apparently this should go with the referenced commit]
Fixes: 00332c16b160 ("s390/ptrace: pass invalid syscall numbers to tracing")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/s390/kernel/ptrace.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -867,6 +867,7 @@ long compat_arch_ptrace(struct task_stru
asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
{
unsigned long mask = -1UL;
+ long ret = -1;

/*
* The sysc_tracesys code in entry.S stored the system
@@ -878,27 +879,33 @@ asmlinkage long do_syscall_trace_enter(s
* Tracing decided this syscall should not happen. Skip
* the system call and the system call restart handling.
*/
- clear_pt_regs_flag(regs, PIF_SYSCALL);
- return -1;
+ goto skip;
}

/* Do the secure computing check after ptrace. */
if (secure_computing(NULL)) {
/* seccomp failures shouldn't expose any additional code. */
- return -1;
+ goto skip;
}

if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
- trace_sys_enter(regs, regs->gprs[2]);
+ trace_sys_enter(regs, regs->int_code & 0xffff);

if (is_compat_task())
mask = 0xffffffff;

- 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)

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