Fix missing audit_syscall_exit() on ppc64 sigsuspend exit path

When we leave sigsuspend() directly into a signal handler, we don't want
to go via the normal syscall exit path -- it'll corrupt r4 and r5 which
are supposed to be giving information to the signal handler, and it'll
give us one more single-step SIGTRAP than we need if single-stepping is
in operation.

However, we _should_ be calling audit_syscall_exit(), which would
normally get invoked in that patch. It's not wonderfully pretty, but I
suspect the best answer is just to call it directly...

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

2 files changed, 13 insertions, 4 deletions

diff --git a/arch/ppc64/kernel/asm-offsets.c b/arch/ppc64/kernel/asm-offsets.c
index abb9e5b5da03..6f910fa2746f 100644
--- a/arch/ppc64/kernel/asm-offsets.c
+++ b/arch/ppc64/kernel/asm-offsets.c
@@ -68,6 +68,7 @@ int main(void)
         DEFINE(THREAD_USED_VR, offsetof(struct thread_struct, used_vr));
 #endif /* CONFIG_ALTIVEC */
         DEFINE(MM, offsetof(struct task_struct, mm));
+        DEFINE(AUDITCONTEXT, offsetof(struct task_struct, audit_context));
 
         DEFINE(DCACHEL1LINESIZE, offsetof(struct ppc64_caches, dline_size));
         DEFINE(DCACHEL1LOGLINESIZE, offsetof(struct ppc64_caches, log_dline_size));
diff --git a/arch/ppc64/kernel/entry.S b/arch/ppc64/kernel/entry.S
index b61572eb2a71..ae5d563ad93a 100644
--- a/arch/ppc64/kernel/entry.S
+++ b/arch/ppc64/kernel/entry.S
@@ -276,12 +276,20 @@ _GLOBAL(ppc64_rt_sigsuspend)
 _GLOBAL(ppc32_rt_sigsuspend)
         bl      .save_nvgprs
         bl      .sys32_rt_sigsuspend
-        /* If sigsuspend() returns zero, we are going into a signal handler */
 70:     cmpdi   0,r3,0
-        beq     .ret_from_except
-        /* If it returned -EINTR, we need to return via syscall_exit to set
+        /* If it returned an error, we need to return via syscall_exit to set
            the SO bit in cr0 and potentially stop for ptrace. */
-        b       syscall_exit
+        bne     syscall_exit
+        /* If sigsuspend() returns zero, we are going into a signal handler. We
+           may need to call audit_syscall_exit() to mark the exit from sigsuspend() */
+        ld      r3,PACACURRENT(r13)
+        ld      r4,AUDITCONTEXT(r3)
+        cmpdi   0,r4,0
+        beq     .ret_from_except        /* No audit_context: Leave immediately. */
+        li      r4, 2                   /* AUDITSC_FAILURE */
+        li      r5,-4                   /* It's always -EINTR */
+        bl      .audit_syscall_exit
+        b       .ret_from_except
 
 _GLOBAL(ppc_fork)
         bl      .save_nvgprs