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authorAndy Lutomirski <luto@kernel.org>2019-05-14 20:24:39 (GMT)
committerIngo Molnar <mingo@kernel.org>2019-05-16 07:05:11 (GMT)
commit88640e1dcd089879530a49a8d212d1814678dfe7 (patch)
treeb3bfb6be2d0f41cef5c8d3b7797f55e70e510c61 /Documentation/x86
parent00f5764dbb040188e5dce2cd9e648360886b045c (diff)
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x86/speculation/mds: Revert CPU buffer clear on double fault exit
The double fault ESPFIX path doesn't return to user mode at all -- it returns back to the kernel by simulating a #GP fault. prepare_exit_to_usermode() will run on the way out of general_protection before running user code. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@suse.de> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jon Masters <jcm@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Fixes: 04dcbdb80578 ("x86/speculation/mds: Clear CPU buffers on exit to user") Link: http://lkml.kernel.org/r/ac97612445c0a44ee10374f6ea79c222fe22a5c4.1557865329.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/x86')
-rw-r--r--Documentation/x86/mds.rst7
1 files changed, 0 insertions, 7 deletions
diff --git a/Documentation/x86/mds.rst b/Documentation/x86/mds.rst
index 534e9ba..0dc812b 100644
--- a/Documentation/x86/mds.rst
+++ b/Documentation/x86/mds.rst
@@ -158,13 +158,6 @@ Mitigation points
mitigated on the return from do_nmi() to provide almost complete
coverage.
- - Double fault (#DF):
-
- A double fault is usually fatal, but the ESPFIX workaround, which can
- be triggered from user space through modify_ldt(2) is a recoverable
- double fault. #DF uses the paranoid exit path, so explicit mitigation
- in the double fault handler is required.
-
- Machine Check Exception (#MC):
Another corner case is a #MC which hits between the CPU buffer clear