x86/nospec: Fix i386 RSB stuffing

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commit 3329249737 upstream.

Turns out that i386 doesn't unconditionally have LFENCE, as such the
loop in __FILL_RETURN_BUFFER isn't actually speculation safe on such
chips.

Fixes: ba6e31af2b ("x86/speculation: Add LFENCE to RSB fill sequence")
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Yv9tj9vbQ9nNlXoY@worktop.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Peter Zijlstra 2022-08-19 13:01:35 +02:00 • committed by Greg Kroah-Hartman

parent 7b0163c1b0

commit b864bc2ad4

1 changed files with 12 additions and 0 deletions

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arch/x86/include/asm/nospec-branch.h

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