x86/fred: Correct speculative safety in fred_extint()

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[ Upstream commit aa280a08e7 ]

array_index_nospec() is no use if the result gets spilled to the stack, as
it makes the believed safe-under-speculation value subject to memory
predictions.

For all practical purposes, this means array_index_nospec() must be used in
the expression that accesses the array.

As the code currently stands, it's the wrong side of irqentry_enter(), and
'index' is put into %ebp across the function call.

Remove the index variable and reposition array_index_nospec(), so it's
calculated immediately before the array access.

Fixes: 14619d912b ("x86/fred: FRED entry/exit and dispatch code")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260106131504.679932-1-andrew.cooper3@citrix.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Andrew Cooper 2026-01-06 13:15:04 +00:00 • committed by Sasha Levin

parent ddbbdebeee

commit e58f1a9b06

1 changed files with 2 additions and 3 deletions

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arch/x86/entry/entry_fred.c

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