diff options
| author | Andrew Cooper <andrew.cooper3@citrix.com> | 2026-01-06 13:15:04 +0000 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-02-23 11:19:11 +0100 |
| commit | aa280a08e7d8fae58557acc345b36b3dc329d595 (patch) | |
| tree | 2deddbd46bb28c0b65fed96a3941bcbca839d14c | |
| parent | 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f (diff) | |
x86/fred: Correct speculative safety in fred_extint()
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: 14619d912b65 ("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
| -rw-r--r-- | arch/x86/entry/entry_fred.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c index a9b72997103d..88c757ac8ccd 100644 --- a/arch/x86/entry/entry_fred.c +++ b/arch/x86/entry/entry_fred.c @@ -160,8 +160,6 @@ void __init fred_complete_exception_setup(void) static noinstr void fred_extint(struct pt_regs *regs) { unsigned int vector = regs->fred_ss.vector; - unsigned int index = array_index_nospec(vector - FIRST_SYSTEM_VECTOR, - NR_SYSTEM_VECTORS); if (WARN_ON_ONCE(vector < FIRST_EXTERNAL_VECTOR)) return; @@ -170,7 +168,8 @@ static noinstr void fred_extint(struct pt_regs *regs) irqentry_state_t state = irqentry_enter(regs); instrumentation_begin(); - sysvec_table[index](regs); + sysvec_table[array_index_nospec(vector - FIRST_SYSTEM_VECTOR, + NR_SYSTEM_VECTORS)](regs); instrumentation_end(); irqentry_exit(regs, state); } else { |