2024-12-27 14:51:17
Linux
PUBLISHED
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 a
flaw: it assumes that unpin_user_pages() handles NULL pages in the pages**
array. Thats not the case, as I discovered when I ran on a new
configuration on my test machine.
Fix this by skipping NULL pages in unpin_user_pages(), just like
unpin_folios() already does.
Details: when booting on x86 with "numa=fake=2 movablecore=4G" on Linux
6.12, and running this:
tools/testing/selftests/mm/gup_longterm
...I get the following crash:
BUG: kernel NULL pointer dereference, address: 0000000000000008
RIP: 0010:sanity_check_pinned_pages+0x3a/0x2d0
...
Call Trace: