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CVE-2024-56612

Description

In the Linux kernel, the following vulnerability has been resolved:mm/gup: handle NULL pages in unpin_user_pages()The recent addition of "pofs" (pages or folios) handling to gup has aflaw: it assumes that unpin_user_pages() handles NULL pages in the pages**array. That's not the case, as I discovered when I ran on a newconfiguration on my test machine.Fix this by skipping NULL pages in unpin_user_pages(), just likeunpin_folios() already does.Details: when booting on x86 with "numa=fake=2 movablecore=4G" on Linux6.12, and running this: tools/testing/selftests/mm/gup_longterm...I get the following crash:BUG: kernel NULL pointer dereference, address: 0000000000000008RIP: 0010:sanity_check_pinned_pages+0x3a/0x2d0...Call Trace: ? __die_body+0x66/0xb0 ? page_fault_oops+0x30c/0x3b0 ? do_user_addr_fault+0x6c3/0x720 ? irqentry_enter+0x34/0x60 ? exc_page_fault+0x68/0x100 ? asm_exc_page_fault+0x22/0x30 ? sanity_check_pinned_pages+0x3a/0x2d0 unpin_user_pages+0x24/0xe0 check_and_migrate_movable_pages_or_folios+0x455/0x4b0 __gup_longterm_locked+0x3bf/0x820 ? mmap_read_lock_killable+0x12/0x50 ? __pfx_mmap_read_lock_killable+0x10/0x10 pin_user_pages+0x66/0xa0 gup_test_ioctl+0x358/0xb20 __se_sys_ioctl+0x6b/0xc0 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x76/0x7e

POC

Reference

No PoCs from references.

Github

- https://github.com/cku-heise/euvd-api-doc