linux-kernel - [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread

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Message-Id: <201204281858.q3SIwC7H014319@farm-0027.internal.tilera.com>
Date:	Sat, 28 Apr 2012 14:51:43 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread

Calling interrupt_return will check the privilege of the context we're
returning to avoid the possibility of kernel threads doing any kind
of userspace actions (including signal handling) after a fork.

Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
---
Al, thanks for noticing this.  I've queued it up for 3.4.

Do you have a case that might provoke the signal behavior in the
unpatched code?  The patched code passes our internal regressions.

 arch/tile/kernel/intvec_32.S |    2 +-
 arch/tile/kernel/intvec_64.S |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/tile/kernel/intvec_32.S b/arch/tile/kernel/intvec_32.S
index 5d56a1e..d0f48ca 100644
--- a/arch/tile/kernel/intvec_32.S
+++ b/arch/tile/kernel/intvec_32.S
@@ -1274,7 +1274,7 @@ STD_ENTRY(ret_from_fork)
 	FEEDBACK_REENTER(ret_from_fork)
 	{
 	 movei  r30, 0               /* not an NMI */
-	 j      .Lresume_userspace   /* jump into middle of interrupt_return */
+	 j      interrupt_return
 	}
 	STD_ENDPROC(ret_from_fork)
 
diff --git a/arch/tile/kernel/intvec_64.S b/arch/tile/kernel/intvec_64.S
index 49d9d66..252924b 100644
--- a/arch/tile/kernel/intvec_64.S
+++ b/arch/tile/kernel/intvec_64.S
@@ -1120,7 +1120,7 @@ STD_ENTRY(ret_from_fork)
 	FEEDBACK_REENTER(ret_from_fork)
 	{
 	 movei  r30, 0               /* not an NMI */
-	 j      .Lresume_userspace   /* jump into middle of interrupt_return */
+	 j      interrupt_return
 	}
 	STD_ENDPROC(ret_from_fork)
 
-- 
1.6.5.2

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