From: Jerome Marchand <jmarchan@redhat.com>
Date: Thu, 19 Feb 2009 14:17:00 +0100
Subject: [ptrace] correctly handle ptrace_update return value
Message-id: 499D5BCC.7010206@redhat.com
O-Subject: [RHEL5.4 Patch] BZ483814: correctly handle ptrace_update() return value
Bugzilla: 483814

Description:
We hit a kernel BUG at kernel/ptrace.c:1068, trying to do a
ptrace(PTRACE_SINGLESTEP,...) when the target exits. In that case, in
ptrace_common(), the call to ptrace_update() returns -EALREADY when we
expect nothing else than 0 or -ESRCH.
The same could happen when doing PTRACE_SETOPTIONS although that may
have never been hit (at least, I never did).

Solution:
Ignore the EALREADY error as it's already done for ESRCH.

Upstream status:
The bug is utrace specific. Upstream is not affected.

Brew:
https://brewweb.devel.redhat.com/taskinfo?taskID=1695481

Test status:
Successfully tested by me using the the reproducer available on BZ.
Only the PTRACE_SINGLESTEP case was tested for I have no reproducer
for it.

Regards,
Jerome

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 53aa435..84e2488 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1066,7 +1066,7 @@ ptrace_common(long request, struct task_struct *child,
 			flags |= UTRACE_ACTION_BLOCKSTEP;
 		ret = ptrace_update(child, state, flags, 1);
 		if (ret)
-			BUG_ON(ret != -ESRCH);
+			BUG_ON(ret != -ESRCH && ret != -EALREADY);
 		ret = 0;
 		break;
 
@@ -1080,7 +1080,7 @@ ptrace_common(long request, struct task_struct *child,
 		state->options = data;
 		ret = ptrace_update(child, state, UTRACE_ACTION_QUIESCE, 1);
 		if (ret)
-			BUG_ON(ret != -ESRCH);
+			BUG_ON(ret != -ESRCH && ret != -EALREADY);
 		ret = 0;
 		break;
 	}