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authorLinus Torvalds <torvalds@linux-foundation.org>2019-04-15 00:09:40 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2019-04-15 00:09:40 +0200
commit6b3a707736301c2128ca85ce85fb13f60b5e350a (patch)
tree2bf1892cf29121150adece8d1221ecd513a4e792 /drivers/usb/host/uhci-grlib.c
parentMerge tag 'for-linus-20190412' of git://git.kernel.dk/linux-block (diff)
parentfs: prevent page refcount overflow in pipe_buf_get (diff)
downloadlinux-6b3a707736301c2128ca85ce85fb13f60b5e350a.tar.xz
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Merge branch 'page-refs' (page ref overflow)
Merge page ref overflow branch. Jann Horn reported that he can overflow the page ref count with sufficient memory (and a filesystem that is intentionally extremely slow). Admittedly it's not exactly easy. To have more than four billion references to a page requires a minimum of 32GB of kernel memory just for the pointers to the pages, much less any metadata to keep track of those pointers. Jann needed a total of 140GB of memory and a specially crafted filesystem that leaves all reads pending (in order to not ever free the page references and just keep adding more). Still, we have a fairly straightforward way to limit the two obvious user-controllable sources of page references: direct-IO like page references gotten through get_user_pages(), and the splice pipe page duplication. So let's just do that. * branch page-refs: fs: prevent page refcount overflow in pipe_buf_get mm: prevent get_user_pages() from overflowing page refcount mm: add 'try_get_page()' helper function mm: make page ref count overflow check tighter and more explicit
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