In the Linux kernel, the following vulnerability has been resolved:
powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit
When __replay_soft_interrupts() replays a pending interrupt (e.g.
PACA_IRQ_DEC -> timer_interrupt), it calls the handler directly with a
synthetic pt_regs. The DEFINE_INTERRUPT_HANDLER_ASYNC wrapper around
each handler calls arch_interrupt_async_exit_prepare() on the way out,
which calls arch_interrupt_exit_prepare() -> local_irq_disable() ->
arch_local_irq_disable(), which does:
irq_soft_mask_set(IRQS_DISABLED) /* 0x1 */
This unconditionally overwrites irq_soft_mask with IRQS_DISABLED (0x1),
stripping the IRQS_PMI_DISABLED (0x2) bit. The result is that
irq_soft_mask is 0x1 instead of IRQS_ALL_DISABLED (0x3) when the
handler returns to __replay_soft_interrupts().
For a normally-taken interrupt this is harmless: the next interrupt
always enters through arch_interrupt_enter_prepare() which
unconditionally sets irq_soft_mask to IRQS_ALL_DISABLED. But during
replay, next_interrupt() is called directly between replayed handlers
without going back through arch_interrupt_enter_prepare(), so the
stripped bit is never restored. next_interrupt() then fires a WARNING:
WARNING: arch/powerpc/kernel/irq_64.c:75
WARN_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED)
The warning was observed early in boot on a POWER10 pseries guest
during kmem_cache_init_late(), where a spinlock release triggers
interrupt replay that processes a pending timer interrupt.
Debugger state confirming the bug:
Before timer_interrupt(®s):
irq_soft_mask = 0x3 (IRQS_ALL_DISABLED) correct
irq_happened = 0x41 (HARD_DIS|REPLAYING) correct
After timer_interrupt(®s) returns:
irq_soft_mask = 0x1 (IRQS_DISABLED) WRONG - PMI bit stripped
irq_happened = 0x41 unchanged
The fix is to replace local_irq_disable() with hard_irq_disable().
hard_irq_disable() is the right primitive here for two reasons:
1. On PPC64 (hw_irq.h:301) it calls irq_soft_mask_set_return(IRQS_ALL_DISABLED),
setting the soft mask to 0x3 (both IRQS_DISABLED and IRQS_PMI_DISABLED),
which preserves the PMI bit and fixes the WARNING. The additional
work it does (__hard_irq_disable(), PACA_IRQ_HARD_DIS |=) is
redundant but safe since both are already set at this point in the
exit path; the trace_hardirqs_off() inside is guarded by
if (!arch_irqs_disabled_flags(flags)) so it will not double-fire.
2. On PPC32 (hw_irq.h:467) hard_irq_disable() maps to
arch_local_irq_disable() -> __hard_irq_disable(), which clears
MSR[EE] in hardware. This is exactly correct: PPC32 has no soft-mask
PACA mechanism, so the hardware disable is the right way to satisfy
irqentry_exit()'s requirement. This also fixes a build error on PPC32
where irq_soft_mask_set() is only defined under CONFIG_PPC64:
arch/powerpc/include/asm/entry-common.h:273: error: implicit
declaration of function 'irq_soft_mask_set'
Using hard_irq_disable() requires no #ifdef and is consistent with
how the rest of the entry code (e.g. entry-common.h:463) handles the
same PPC32/PPC64 split.
powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit
When __replay_soft_interrupts() replays a pending interrupt (e.g.
PACA_IRQ_DEC -> timer_interrupt), it calls the handler directly with a
synthetic pt_regs. The DEFINE_INTERRUPT_HANDLER_ASYNC wrapper around
each handler calls arch_interrupt_async_exit_prepare() on the way out,
which calls arch_interrupt_exit_prepare() -> local_irq_disable() ->
arch_local_irq_disable(), which does:
irq_soft_mask_set(IRQS_DISABLED) /* 0x1 */
This unconditionally overwrites irq_soft_mask with IRQS_DISABLED (0x1),
stripping the IRQS_PMI_DISABLED (0x2) bit. The result is that
irq_soft_mask is 0x1 instead of IRQS_ALL_DISABLED (0x3) when the
handler returns to __replay_soft_interrupts().
For a normally-taken interrupt this is harmless: the next interrupt
always enters through arch_interrupt_enter_prepare() which
unconditionally sets irq_soft_mask to IRQS_ALL_DISABLED. But during
replay, next_interrupt() is called directly between replayed handlers
without going back through arch_interrupt_enter_prepare(), so the
stripped bit is never restored. next_interrupt() then fires a WARNING:
WARNING: arch/powerpc/kernel/irq_64.c:75
WARN_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED)
The warning was observed early in boot on a POWER10 pseries guest
during kmem_cache_init_late(), where a spinlock release triggers
interrupt replay that processes a pending timer interrupt.
Debugger state confirming the bug:
Before timer_interrupt(®s):
irq_soft_mask = 0x3 (IRQS_ALL_DISABLED) correct
irq_happened = 0x41 (HARD_DIS|REPLAYING) correct
After timer_interrupt(®s) returns:
irq_soft_mask = 0x1 (IRQS_DISABLED) WRONG - PMI bit stripped
irq_happened = 0x41 unchanged
The fix is to replace local_irq_disable() with hard_irq_disable().
hard_irq_disable() is the right primitive here for two reasons:
1. On PPC64 (hw_irq.h:301) it calls irq_soft_mask_set_return(IRQS_ALL_DISABLED),
setting the soft mask to 0x3 (both IRQS_DISABLED and IRQS_PMI_DISABLED),
which preserves the PMI bit and fixes the WARNING. The additional
work it does (__hard_irq_disable(), PACA_IRQ_HARD_DIS |=) is
redundant but safe since both are already set at this point in the
exit path; the trace_hardirqs_off() inside is guarded by
if (!arch_irqs_disabled_flags(flags)) so it will not double-fire.
2. On PPC32 (hw_irq.h:467) hard_irq_disable() maps to
arch_local_irq_disable() -> __hard_irq_disable(), which clears
MSR[EE] in hardware. This is exactly correct: PPC32 has no soft-mask
PACA mechanism, so the hardware disable is the right way to satisfy
irqentry_exit()'s requirement. This also fixes a build error on PPC32
where irq_soft_mask_set() is only defined under CONFIG_PPC64:
arch/powerpc/include/asm/entry-common.h:273: error: implicit
declaration of function 'irq_soft_mask_set'
Using hard_irq_disable() requires no #ifdef and is consistent with
how the rest of the entry code (e.g. entry-common.h:463) handles the
same PPC32/PPC64 split.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||
| Linux | Linux | affected |
|
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Fixes
Solution
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Workaround
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References
History
Wed, 14 Oct 2026 13:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit When __replay_soft_interrupts() replays a pending interrupt (e.g. PACA_IRQ_DEC -> timer_interrupt), it calls the handler directly with a synthetic pt_regs. The DEFINE_INTERRUPT_HANDLER_ASYNC wrapper around each handler calls arch_interrupt_async_exit_prepare() on the way out, which calls arch_interrupt_exit_prepare() -> local_irq_disable() -> arch_local_irq_disable(), which does: irq_soft_mask_set(IRQS_DISABLED) /* 0x1 */ This unconditionally overwrites irq_soft_mask with IRQS_DISABLED (0x1), stripping the IRQS_PMI_DISABLED (0x2) bit. The result is that irq_soft_mask is 0x1 instead of IRQS_ALL_DISABLED (0x3) when the handler returns to __replay_soft_interrupts(). For a normally-taken interrupt this is harmless: the next interrupt always enters through arch_interrupt_enter_prepare() which unconditionally sets irq_soft_mask to IRQS_ALL_DISABLED. But during replay, next_interrupt() is called directly between replayed handlers without going back through arch_interrupt_enter_prepare(), so the stripped bit is never restored. next_interrupt() then fires a WARNING: WARNING: arch/powerpc/kernel/irq_64.c:75 WARN_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED) The warning was observed early in boot on a POWER10 pseries guest during kmem_cache_init_late(), where a spinlock release triggers interrupt replay that processes a pending timer interrupt. Debugger state confirming the bug: Before timer_interrupt(®s): irq_soft_mask = 0x3 (IRQS_ALL_DISABLED) correct irq_happened = 0x41 (HARD_DIS|REPLAYING) correct After timer_interrupt(®s) returns: irq_soft_mask = 0x1 (IRQS_DISABLED) WRONG - PMI bit stripped irq_happened = 0x41 unchanged The fix is to replace local_irq_disable() with hard_irq_disable(). hard_irq_disable() is the right primitive here for two reasons: 1. On PPC64 (hw_irq.h:301) it calls irq_soft_mask_set_return(IRQS_ALL_DISABLED), setting the soft mask to 0x3 (both IRQS_DISABLED and IRQS_PMI_DISABLED), which preserves the PMI bit and fixes the WARNING. The additional work it does (__hard_irq_disable(), PACA_IRQ_HARD_DIS |=) is redundant but safe since both are already set at this point in the exit path; the trace_hardirqs_off() inside is guarded by if (!arch_irqs_disabled_flags(flags)) so it will not double-fire. 2. On PPC32 (hw_irq.h:467) hard_irq_disable() maps to arch_local_irq_disable() -> __hard_irq_disable(), which clears MSR[EE] in hardware. This is exactly correct: PPC32 has no soft-mask PACA mechanism, so the hardware disable is the right way to satisfy irqentry_exit()'s requirement. This also fixes a build error on PPC32 where irq_soft_mask_set() is only defined under CONFIG_PPC64: arch/powerpc/include/asm/entry-common.h:273: error: implicit declaration of function 'irq_soft_mask_set' Using hard_irq_disable() requires no #ifdef and is consistent with how the rest of the entry code (e.g. entry-common.h:463) handles the same PPC32/PPC64 split. | |
| Title | powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-14T13:25:57.887Z
Reserved: 2026-09-25T10:25:14.346Z
Link: CVE-2026-98395
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-14T14:17:50.407
Modified: 2026-10-14T14:17:50.407
Link: CVE-2026-98395
Redhat
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OpenCVE Enrichment
No data.
Weaknesses
No weakness.