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Considering this case:
1. A program opens a sysfs table file 65535 times, it can increase
validation_count and first increment cause the table to be mapped:
validation_count = 65535
2. AML execution causes "Load" to be executed on the same
table, this time it cannot increase validation_count, so
validation_count remains:
validation_count = 65535
3. The program closes sysfs table file 65535 times, it can decrease
validation_count and the last decrement cause the table to be
unmapped:
validation_count = 0
4. AML code still accessing the loaded table, kernel crash can be
observed.
To prevent that from happening, add a validation_count threashold.
When it is reached, the validation_count can no longer be
incremented/decremented to invalidate the table descriptor (means
preventing table unmappings)
Note that code added in acpi_tb_put_table() is actually a no-op but
changes the warning message into a "warn once" one. Lv Zheng.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
[ rjw: Changelog, comments ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| dt-bindings | ||
| keys | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rxrpc | ||
| scsi | ||
| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| video | ||
| xen | ||
| Kbuild | ||