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Koen Kooi
bb34e69f3d
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net> Signed-off-by: Denys Dmytriyenko <denys@ti.com>
86 lines
2.6 KiB
Diff
86 lines
2.6 KiB
Diff
From 37d297b39726f3284da2f83d235c94b0d224e047 Mon Sep 17 00:00:00 2001
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From: Dmitry Adamushko <dmitry.adamushko@gmail.com>
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Date: Thu, 22 Mar 2012 21:39:25 +0100
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Subject: [PATCH 097/147] x86-32: Fix endless loop when processing signals for
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kernel tasks
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commit 29a2e2836ff9ea65a603c89df217f4198973a74f upstream.
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The problem occurs on !CONFIG_VM86 kernels [1] when a kernel-mode task
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returns from a system call with a pending signal.
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A real-life scenario is a child of 'khelper' returning from a failed
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kernel_execve() in ____call_usermodehelper() [ kernel/kmod.c ].
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kernel_execve() fails due to a pending SIGKILL, which is the result of
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"kill -9 -1" (at least, busybox's init does it upon reboot).
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The loop is as follows:
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* syscall_exit_work:
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- work_pending: // start_of_the_loop
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- work_notify_sig:
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- do_notify_resume()
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- do_signal()
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- if (!user_mode(regs)) return;
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- resume_userspace // TIF_SIGPENDING is still set
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- work_pending // so we call work_pending => goto
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// start_of_the_loop
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More information can be found in another LKML thread:
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http://www.serverphorums.com/read.php?12,457826
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[1] the problem was also seen on MIPS.
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Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
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Link: http://lkml.kernel.org/r/1332448765.2299.68.camel@dimm
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Cc: Oleg Nesterov <oleg@redhat.com>
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Cc: Roland McGrath <roland@hack.frob.com>
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Cc: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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arch/x86/kernel/entry_32.S | 17 ++++++++++-------
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1 file changed, 10 insertions(+), 7 deletions(-)
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diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
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index f3f6f53..bcda816 100644
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--- a/arch/x86/kernel/entry_32.S
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+++ b/arch/x86/kernel/entry_32.S
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@@ -99,12 +99,6 @@
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#endif
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.endm
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-#ifdef CONFIG_VM86
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-#define resume_userspace_sig check_userspace
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-#else
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-#define resume_userspace_sig resume_userspace
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-#endif
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-
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/*
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* User gs save/restore
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*
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@@ -328,10 +322,19 @@ ret_from_exception:
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preempt_stop(CLBR_ANY)
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ret_from_intr:
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GET_THREAD_INFO(%ebp)
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-check_userspace:
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+resume_userspace_sig:
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+#ifdef CONFIG_VM86
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movl PT_EFLAGS(%esp), %eax # mix EFLAGS and CS
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movb PT_CS(%esp), %al
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andl $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax
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+#else
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+ /*
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+ * We can be coming here from a syscall done in the kernel space,
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+ * e.g. a failed kernel_execve().
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+ */
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+ movl PT_CS(%esp), %eax
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+ andl $SEGMENT_RPL_MASK, %eax
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+#endif
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cmpl $USER_RPL, %eax
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jb resume_kernel # not returning to v8086 or userspace
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--
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1.7.9.4
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