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dosirq.c (irq_hook): cache handler_size, avoid use-after-free for djgpp #81

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Merged
sezero merged 1 commit into from
Feb 26, 2026
Merged

dosirq.c (irq_hook): cache handler_size, avoid use-after-free for djgpp #81

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8 changes: 5 additions & 3 deletions src/dos/dosirq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,7 @@ struct irq_handle *irq_hook(int irqno, irq_handler handler, irq_handler end)
__dpmi_version_ret version;
_go32_dpmi_seginfo info;
unsigned long old_sel, old_ofs;
unsigned long size;

__dpmi_get_version(&version);
if (irqno < 8)
Expand All @@ -153,14 +154,15 @@ struct irq_handle *irq_hook(int irqno, irq_handler handler, irq_handler end)
return NULL;

/* Lock the interrupt handler in memory */
if (dpmi_lock_linear_region_base((void *)handler, (unsigned long)end - (unsigned long)handler)) {
size = (unsigned long)end - (unsigned long)handler;
if (dpmi_lock_linear_region_base((void *)handler, size)) {
_free_iret_wrapper(&info);
return NULL;
}

irq = (struct irq_handle *) malloc(sizeof(struct irq_handle));
irq->c_handler = handler;
irq->handler_size = (unsigned long)end - (unsigned long)handler;
irq->handler_size = size;
irq->handler = info.pm_offset;
irq->prev_selector = old_sel;
irq->prev_offset = old_ofs;
Expand All @@ -170,7 +172,7 @@ struct irq_handle *irq_hook(int irqno, irq_handler handler, irq_handler end)

if (dpmi_lock_linear_region_base(irq, sizeof(struct irq_handle))) {
free(irq);
dpmi_unlock_linear_region_base((void *)handler, irq->handler_size);
dpmi_unlock_linear_region_base((void *)handler, size);
_free_iret_wrapper(&info);
return NULL;
}
Expand Down