Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Wed, 23 May 2012 13:16:36 -0500 | From | Dimitri Sivanich <> | Subject | Re: [PATCH] x86: check for valid irq_cfg pointer in smp_irq_move_cleanup_interrupt |
| |
On Mon, May 21, 2012 at 11:34:32PM +0200, Thomas Gleixner wrote: > Don't misunderstand me. The patch is correct, just the explanation > sucks. > Hopefully this explanation is descriptive enough.
A NULL pointer dereference can occur in smp_irq_move_cleanup_interrupt() if we haven't yet setup the irq_cfg pointer in the irq_desc.irq_data.chip_data.
In create_irq_nr() there is a window where we have set vector_irq in __assign_irq_vector(), but not yet called irq_set_chip_data() to set the irq_cfg pointer.
Should an IRQ_MOVE_CLEANUP_VECTOR hit the cpu in question during this time, smp_irq_move_cleanup_interrupt() will attempt to process the aforementioned irq, but panic when accessing irq_cfg.
Only continue processing the irq if irq_cfg is non-NULL.
Signed-off-by: Dimitri Sivanich <sivanich@sgi.com> --- arch/x86/kernel/apic/io_apic.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
Index: linux/arch/x86/kernel/apic/io_apic.c =================================================================== --- linux.orig/arch/x86/kernel/apic/io_apic.c +++ linux/arch/x86/kernel/apic/io_apic.c @@ -2478,9 +2478,12 @@ asmlinkage void smp_irq_move_cleanup_int if (!desc) continue; - cfg = irq_cfg(irq); raw_spin_lock(&desc->lock); + cfg = irq_cfg(irq); + if (!cfg) + goto unlock; + /* * Check if the irq migration is in progress. If so, we * haven't received the cleanup request yet for this irq.
| ![\](/images/icornerr.gif) |