x86-64: Clear a 64-bit FS/GS base on fork if selector is nonzero
commit7ce5a2b9bb2e92902230e3121d8c3047fab9cb47
authorH. Peter Anvin <hpa@zytor.com>
Fri, 23 Apr 2010 23:17:40 +0000 (23 16:17 -0700)
committerH. Peter Anvin <hpa@zytor.com>
Fri, 23 Apr 2010 23:49:51 +0000 (23 16:49 -0700)
treee8741ea11f5644d4a49ef9e4b66820977d577d3f
parentae7c9b70dcb4313ea3dbcc9a2f240dae6c2b50c0
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