Gitweb: http://git.kernel.org/linus/7ce5a2b9bb2e92902230e3121d8c3047fab9cb47
Commit: 7ce5a2b9bb2e92902230e3121d8c3047fab9cb47
Parent: ae7c9b70dcb4313ea3dbcc9a2f240dae6c2b50c0
Author: H. Peter Anvin <hpa@zytor.com>
AuthorDate: Fri Apr 23 16:17:40 2010 -0700
Committer: H. Peter Anvin <hpa@zytor.com>
CommitDate: Fri Apr 23 16:49:51 2010 -0700
x86-64: Clear a 64-bit FS/GS base on fork if selector is nonzero
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>
Cc: <stable@kernel.org>
---
arch/x86/kernel/process_64.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index dc9690b..17cb329 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -276,12 +276,12 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
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);
--
