Messages in this thread Patch in this message | | | Date | Mon, 10 May 2010 15:32:21 -0700 | From | Greg KH <> | Subject | [050/117] x86-64: Clear a 64-bit FS/GS base on fork if selector is nonzero |
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2.6.33-stable review patch. If anyone has any objections, please let us know.
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From: H. Peter Anvin <hpa@zytor.com>
commit 7ce5a2b9bb2e92902230e3121d8c3047fab9cb47 upstream.
When we do a thread switch, we clear the outgoing FS/GS base if the corresponding selector is nonzero. This is taken by __switch_to() as an entry invariant; it does not verify that it is true on entry. However, copy_thread() doesn't enforce this constraint, which can result in inconsistent results after fork().
Make copy_thread() match the behavior of __switch_to().
Reported-and-tested-by: Samuel Thibault <samuel.thibault@inria.fr> Signed-off-by: H. Peter Anvin <hpa@zytor.com> LKML-Reference: <4BD1E061.8030605@zytor.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/x86/kernel/process_64.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -282,12 +282,12 @@ int copy_thread(unsigned long clone_flag set_tsk_thread_flag(p, TIF_FORK); - p->thread.fs = me->thread.fs; - p->thread.gs = me->thread.gs; p->thread.io_bitmap_ptr = NULL; savesegment(gs, p->thread.gsindex); + p->thread.gs = p->thread.gsindex ? 0 : me->thread.gs; savesegment(fs, p->thread.fsindex); + p->thread.fs = p->thread.fsindex ? 0 : me->thread.fs; savesegment(es, p->thread.es); savesegment(ds, p->thread.ds);
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