um/ptrace: Fix the syscall_trace_leave call

Keep the same semantic as before the commit 26703c636c1f: deallocate
audit context and fake a proper syscall exit.

This fix a kernel panic triggered by the seccomp_bpf test:
> [ RUN      ] global.ERRNO_valid
> BUG: failure at kernel/auditsc.c:1504/__audit_syscall_entry()!
> Kernel panic - not syncing: BUG!

Fixes: 26703c636c1f ("um/ptrace: run seccomp after ptrace")

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: James Morris <jmorris@namei.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index ef4b8f949b51..0728fee94398 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -21,11 +21,11 @@ void handle_syscall(struct uml_pt_regs *r)
         PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS);
 
         if (syscall_trace_enter(regs))
-                return;
+                goto out;
 
         /* Do the seccomp check after ptrace; failures should be fast. */
         if (secure_computing(NULL) == -1)
-                return;
+                goto out;
 
         /* Update the syscall number after orig_ax has potentially been updated
          * with ptrace.
@@ -37,5 +37,6 @@ void handle_syscall(struct uml_pt_regs *r)
                 PT_REGS_SET_SYSCALL_RETURN(regs,
                                 EXECUTE_SYSCALL(syscall, regs));
 
+out:
         syscall_trace_leave(regs);
 }