Уязвимость функции jbd2_journal_dirty_metadata() ядра операционной системы Linux, позволяющая нарушителю вызвать отказ в обслуживании

Уязвимость в реализации системного вызова mremap() ядра операционной системы Linux, позволяющая нарушителю получить доступ к физической странице

A flaw was found in the Linux kernel's ext4 filesystem. A local user can cause an out-of-bounds write in jbd2_journal_dirty_metadata(), a denial of service, and a system crash by mounting and operating on a crafted ext4 filesystem image.

Since Linux kernel version 3.2, the mremap() syscall performs TLB flushes after dropping pagetable locks. If a syscall such as ftruncate() removes entries from the pagetables of a task that is in the middle of mremap(), a stale TLB entry can remain for a short time that permits access to a physical page after it has been released back to the page allocator and reused. This is fixed in the following kernel versions: 4.9.135, 4.14.78, 4.18.16, 4.19.