kernel/linux.git/mm/gup.c, branch v4.4.275

mm: prevent get_user_pages() from overflowing page refcount

2020-03-11T06:51:15+00:00

commit 8fde12ca79aff9b5ba951fce1a2641901b8d8e64 upstream. If the page refcount wraps around past zero, it will be freed while there are still four billion references to it. One of the possible avenues for an attacker to try to make this happen is by doing direct IO on a page multiple times. This patch makes get_user_pages() refuse to take a new page reference if there are already more than two billion references to the page. Reported-by: Jann Horn Acked-by: Matthew Wilcox Cc: stable@kernel.org Signed-off-by: Linus Torvalds [ 4.4.y backport notes: Ajay: - Added local variable 'err' with-in follow_hugetlb_page() from 2be7cfed995e, to resolve compilation error - Added page_ref_count() - Added missing refcount overflow checks on x86 and s390 (Vlastimil, thanks for this change) Srivatsa: - Replaced call to get_page_foll() with try_get_page_foll() ] Signed-off-by: Srivatsa S. Bhat (VMware) Signed-off-by: Ajay Kaher Signed-off-by: Vlastimil Babka Signed-off-by: Greg Kroah-Hartman

mm, gup: ensure real head page is ref-counted when using hugepages

2020-03-11T06:51:15+00:00

commit d63206ee32b6e64b0e12d46e5d6004afd9913713 upstream. When speculatively taking references to a hugepage using page_cache_add_speculative() in gup_huge_pmd(), it is assumed that the page returned by pmd_page() is the head page. Although normally true, this assumption doesn't hold when the hugepage comprises of successive page table entries such as when using contiguous bit on arm64 at PTE or PMD levels. This can be addressed by ensuring that the page passed to page_cache_add_speculative() is the real head or by de-referencing the head page within the function. We take the first approach to keep the usage pattern aligned with page_cache_get_speculative() where users already pass the appropriate page, i.e., the de-referenced head. Apply the same logic to fix gup_huge_[pud|pgd]() as well. [punit.agrawal@arm.com: fix arm64 ltp failure] Link: http://lkml.kernel.org/r/20170619170145.25577-5-punit.agrawal@arm.com Link: http://lkml.kernel.org/r/20170522133604.11392-3-punit.agrawal@arm.com Signed-off-by: Punit Agrawal Acked-by: Steve Capper Cc: Michal Hocko Cc: "Kirill A. Shutemov" Cc: Aneesh Kumar K.V Cc: Catalin Marinas Cc: Will Deacon Cc: Naoya Horiguchi Cc: Mark Rutland Cc: Hillf Danton Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ajay Kaher Signed-off-by: Vlastimil Babka Signed-off-by: Greg Kroah-Hartman

mm, gup: remove broken VM_BUG_ON_PAGE compound check for hugepages

2020-03-11T06:51:15+00:00

commit a3e328556d41bb61c55f9dfcc62d6a826ea97b85 upstream. When operating on hugepages with DEBUG_VM enabled, the GUP code checks the compound head for each tail page prior to calling page_cache_add_speculative. This is broken, because on the fast-GUP path (where we don't hold any page table locks) we can be racing with a concurrent invocation of split_huge_page_to_list. split_huge_page_to_list deals with this race by using page_ref_freeze to freeze the page and force concurrent GUPs to fail whilst the component pages are modified. This modification includes clearing the compound_head field for the tail pages, so checking this prior to a successful call to page_cache_add_speculative can lead to false positives: In fact, page_cache_add_speculative *already* has this check once the page refcount has been successfully updated, so we can simply remove the broken calls to VM_BUG_ON_PAGE. Link: http://lkml.kernel.org/r/20170522133604.11392-2-punit.agrawal@arm.com Signed-off-by: Will Deacon Signed-off-by: Punit Agrawal Acked-by: Steve Capper Acked-by: Kirill A. Shutemov Cc: Aneesh Kumar K.V Cc: Catalin Marinas Cc: Naoya Horiguchi Cc: Mark Rutland Cc: Hillf Danton Cc: Michal Hocko Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Srivatsa S. Bhat (VMware) Signed-off-by: Ajay Kaher Signed-off-by: Vlastimil Babka Signed-off-by: Greg Kroah-Hartman

proc: do not access cmdline nor environ from file-backed areas

2018-12-17T20:55:17+00:00

commit 7f7ccc2ccc2e70c6054685f5e3522efa81556830 upstream. proc_pid_cmdline_read() and environ_read() directly access the target process' VM to retrieve the command line and environment. If this process remaps these areas onto a file via mmap(), the requesting process may experience various issues such as extra delays if the underlying device is slow to respond. Let's simply refuse to access file-backed areas in these functions. For this we add a new FOLL_ANON gup flag that is passed to all calls to access_remote_vm(). The code already takes care of such failures (including unmapped areas). Accesses via /proc/pid/mem were not changed though. This was assigned CVE-2018-1120. Note for stable backports: the patch may apply to kernels prior to 4.11 but silently miss one location; it must be checked that no call to access_remote_vm() keeps zero as the last argument. Reported-by: Qualys Security Advisory Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Oleg Nesterov Signed-off-by: Willy Tarreau Signed-off-by: Linus Torvalds [bwh: Backported to 4.4: - Update the extra call to access_remote_vm() from proc_pid_cmdline_read() - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

mm: replace get_user_pages() write/force parameters with gup_flags

2018-12-17T20:55:16+00:00

commit 768ae309a96103ed02eb1e111e838c87854d8b51 upstream. This removes the 'write' and 'force' from get_user_pages() and replaces them with 'gup_flags' to make the use of FOLL_FORCE explicit in callers as use of this flag can result in surprising behaviour (and hence bugs) within the mm subsystem. Signed-off-by: Lorenzo Stoakes Acked-by: Christian König Acked-by: Jesper Nilsson Acked-by: Michal Hocko Reviewed-by: Jan Kara Signed-off-by: Linus Torvalds [bwh: Backported to 4.4: - Drop changes in rapidio, vchiq, goldfish - Keep the "write" variable in amdgpu_ttm_tt_pin_userptr() as it's still needed - Also update calls from various other places that now use get_user_pages_remote() upstream, which were updated there by commit 9beae1ea8930 "mm: replace get_user_pages_remote() write/force ..." - Also update calls from hfi1 and ipath - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

mm: replace get_user_pages_locked() write/force parameters with gup_flags

2018-12-17T20:55:16+00:00

commit 3b913179c3fa89dd0e304193fa0c746fc0481447 upstream. This removes the 'write' and 'force' use from get_user_pages_locked() and replaces them with 'gup_flags' to make the use of FOLL_FORCE explicit in callers as use of this flag can result in surprising behaviour (and hence bugs) within the mm subsystem. Signed-off-by: Lorenzo Stoakes Acked-by: Michal Hocko Reviewed-by: Jan Kara Signed-off-by: Linus Torvalds [bwh: Backported to 4.4: adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

mm: replace get_user_pages_unlocked() write/force parameters with gup_flags

2018-12-17T20:55:16+00:00

commit c164154f66f0c9b02673f07aa4f044f1d9c70274 upstream. This removes the 'write' and 'force' use from get_user_pages_unlocked() and replaces them with 'gup_flags' to make the use of FOLL_FORCE explicit in callers as use of this flag can result in surprising behaviour (and hence bugs) within the mm subsystem. Signed-off-by: Lorenzo Stoakes Reviewed-by: Jan Kara Acked-by: Michal Hocko Signed-off-by: Linus Torvalds [bwh: Backported to 4.4: - Also update calls from process_vm_rw_single_vec() and async_pf_execute() - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

mm: remove write/force parameters from __get_user_pages_unlocked()

2018-12-17T20:55:16+00:00

commit d4944b0ecec0af882483fe44b66729316e575208 upstream. This removes the redundant 'write' and 'force' parameters from __get_user_pages_unlocked() to make the use of FOLL_FORCE explicit in callers as use of this flag can result in surprising behaviour (and hence bugs) within the mm subsystem. Signed-off-by: Lorenzo Stoakes Acked-by: Paolo Bonzini Reviewed-by: Jan Kara Acked-by: Michal Hocko Signed-off-by: Linus Torvalds [bwh: Backported to 4.4: - Defer changes in process_vm_rw_single_vec() and async_pf_execute() since they use get_user_pages_unlocked() here - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

mm: remove write/force parameters from __get_user_pages_locked()

2018-12-17T20:55:16+00:00

commit 859110d7497cdd0e6b21010d6f777049d676382c upstream. This removes the redundant 'write' and 'force' parameters from __get_user_pages_locked() to make the use of FOLL_FORCE explicit in callers as use of this flag can result in surprising behaviour (and hence bugs) within the mm subsystem. Signed-off-by: Lorenzo Stoakes Reviewed-by: Jan Kara Acked-by: Michal Hocko Signed-off-by: Linus Torvalds [bwh: Backported to 4.4: - Drop change in get_user_pages_remote() - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

mm: do not bug_on on incorrect length in __mm_populate()

2018-11-21T08:27:41+00:00

commit bb177a732c4369bb58a1fe1df8f552b6f0f7db5f upstream. syzbot has noticed that a specially crafted library can easily hit VM_BUG_ON in __mm_populate kernel BUG at mm/gup.c:1242! invalid opcode: 0000 [#1] SMP CPU: 2 PID: 9667 Comm: a.out Not tainted 4.18.0-rc3 #644 Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/19/2017 RIP: 0010:__mm_populate+0x1e2/0x1f0 Code: 55 d0 65 48 33 14 25 28 00 00 00 89 d8 75 21 48 83 c4 20 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 75 18 f1 ff 0f 0b e8 6e 18 f1 ff <0f> 0b 31 db eb c9 e8 93 06 e0 ff 0f 1f 00 55 48 89 e5 53 48 89 fb Call Trace: vm_brk_flags+0xc3/0x100 vm_brk+0x1f/0x30 load_elf_library+0x281/0x2e0 __ia32_sys_uselib+0x170/0x1e0 do_fast_syscall_32+0xca/0x420 entry_SYSENTER_compat+0x70/0x7f The reason is that the length of the new brk is not page aligned when we try to populate the it. There is no reason to bug on that though. do_brk_flags already aligns the length properly so the mapping is expanded as it should. All we need is to tell mm_populate about it. Besides that there is absolutely no reason to to bug_on in the first place. The worst thing that could happen is that the last page wouldn't get populated and that is far from putting system into an inconsistent state. Fix the issue by moving the length sanitization code from do_brk_flags up to vm_brk_flags. The only other caller of do_brk_flags is brk syscall entry and it makes sure to provide the proper length so t here is no need for sanitation and so we can use do_brk_flags without it. Also remove the bogus BUG_ONs. [osalvador@techadventures.net: fix up vm_brk_flags s@request@len@] Link: http://lkml.kernel.org/r/20180706090217.GI32658@dhcp22.suse.cz Signed-off-by: Michal Hocko Reported-by: syzbot Tested-by: Tetsuo Handa Reviewed-by: Oscar Salvador Cc: Zi Yan Cc: "Aneesh Kumar K.V" Cc: Dan Williams Cc: "Kirill A. Shutemov" Cc: Michael S. Tsirkin Cc: Al Viro Cc: "Huang, Ying" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 4.4: - There is no do_brk_flags() function; update do_brk() - do_brk(), vm_brk() return the address on success - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Sasha Levin