user/sven/linux.git/include/linux/mm.h, branch v5.4.63

mm: add kvfree_sensitive() for freeing sensitive data objects

2020-06-17T14:40:23Z

[ Upstream commit d4eaa2837851db2bfed572898bfc17f9a9f9151e ] For kvmalloc'ed data object that contains sensitive information like cryptographic keys, we need to make sure that the buffer is always cleared before freeing it. Using memset() alone for buffer clearing may not provide certainty as the compiler may compile it away. To be sure, the special memzero_explicit() has to be used. This patch introduces a new kvfree_sensitive() for freeing those sensitive data objects allocated by kvmalloc(). The relevant places where kvfree_sensitive() can be used are modified to use it. Fixes: 4f0882491a14 ("KEYS: Avoid false positive ENOMEM error on key read") Suggested-by: Linus Torvalds Signed-off-by: Waiman Long Signed-off-by: Andrew Morton Reviewed-by: Eric Biggers Acked-by: David Howells Cc: Jarkko Sakkinen Cc: James Morris Cc: "Serge E. Hallyn" Cc: Joe Perches Cc: Matthew Wilcox Cc: David Rientjes Cc: Uladzislau Rezki Link: http://lkml.kernel.org/r/20200407200318.11711-1-longman@redhat.com Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

mm: remove VM_BUG_ON(PageSlab()) from page_mapcount()

2020-06-03T06:21:26Z

[ Upstream commit 6988f31d558aa8c744464a7f6d91d34ada48ad12 ] Replace superfluous VM_BUG_ON() with comment about correct usage. Technically reverts commit 1d148e218a0d ("mm: add VM_BUG_ON_PAGE() to page_mapcount()"), but context lines have changed. Function isolate_migratepages_block() runs some checks out of lru_lock when choose pages for migration. After checking PageLRU() it checks extra page references by comparing page_count() and page_mapcount(). Between these two checks page could be removed from lru, freed and taken by slab. As a result this race triggers VM_BUG_ON(PageSlab()) in page_mapcount(). Race window is tiny. For certain workload this happens around once a year. page:ffffea0105ca9380 count:1 mapcount:0 mapping:ffff88ff7712c180 index:0x0 compound_mapcount: 0 flags: 0x500000000008100(slab|head) raw: 0500000000008100 dead000000000100 dead000000000200 ffff88ff7712c180 raw: 0000000000000000 0000000080200020 00000001ffffffff 0000000000000000 page dumped because: VM_BUG_ON_PAGE(PageSlab(page)) ------------[ cut here ]------------ kernel BUG at ./include/linux/mm.h:628! invalid opcode: 0000 [#1] SMP NOPTI CPU: 77 PID: 504 Comm: kcompactd1 Tainted: G W 4.19.109-27 #1 Hardware name: Yandex T175-N41-Y3N/MY81-EX0-Y3N, BIOS R05 06/20/2019 RIP: 0010:isolate_migratepages_block+0x986/0x9b0 The code in isolate_migratepages_block() was added in commit 119d6d59dcc0 ("mm, compaction: avoid isolating pinned pages") before adding VM_BUG_ON into page_mapcount(). This race has been predicted in 2015 by Vlastimil Babka (see link below). [akpm@linux-foundation.org: comment tweaks, per Hugh] Fixes: 1d148e218a0d ("mm: add VM_BUG_ON_PAGE() to page_mapcount()") Signed-off-by: Konstantin Khlebnikov Signed-off-by: Andrew Morton Acked-by: Hugh Dickins Acked-by: Kirill A. Shutemov Acked-by: Vlastimil Babka Cc: David Rientjes Cc: Link: http://lkml.kernel.org/r/159032779896.957378.7852761411265662220.stgit@buzz Link: https://lore.kernel.org/lkml/557710E1.6060103@suse.cz/ Link: https://lore.kernel.org/linux-mm/158937872515.474360.5066096871639561424.stgit@buzz/T/ (v1) Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

mm, hotplug: fix page online with DEBUG_PAGEALLOC compiled but not enabled

2020-03-12T12:00:19Z

commit c87cbc1f007c4b46165f05ceca04e1973cda0b9c upstream. Commit cd02cf1aceea ("mm/hotplug: fix an imbalance with DEBUG_PAGEALLOC") fixed memory hotplug with debug_pagealloc enabled, where onlining a page goes through page freeing, which removes the direct mapping. Some arches don't like when the page is not mapped in the first place, so generic_online_page() maps it first. This is somewhat wasteful, but better than special casing page freeing fast paths. The commit however missed that DEBUG_PAGEALLOC configured doesn't mean it's actually enabled. One has to test debug_pagealloc_enabled() since 031bc5743f15 ("mm/debug-pagealloc: make debug-pagealloc boottime configurable"), or alternatively debug_pagealloc_enabled_static() since 8e57f8acbbd1 ("mm, debug_pagealloc: don't rely on static keys too early"), but this is not done. As a result, a s390 kernel with DEBUG_PAGEALLOC configured but not enabled will crash: Unable to handle kernel pointer dereference in virtual kernel address space Failing address: 0000000000000000 TEID: 0000000000000483 Fault in home space mode while using kernel ASCE. AS:0000001ece13400b R2:000003fff7fd000b R3:000003fff7fcc007 S:000003fff7fd7000 P:000000000000013d Oops: 0004 ilc:2 [#1] SMP CPU: 1 PID: 26015 Comm: chmem Kdump: loaded Tainted: GX 5.3.18-5-default #1 SLE15-SP2 (unreleased) Krnl PSW : 0704e00180000000 0000001ecd281b9e (__kernel_map_pages+0x166/0x188) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000000 0000000000000800 0000400b00000000 0000000000000100 0000000000000001 0000000000000000 0000000000000002 0000000000000100 0000001ece139230 0000001ecdd98d40 0000400b00000100 0000000000000000 000003ffa17e4000 001fffe0114f7d08 0000001ecd4d93ea 001fffe0114f7b20 Krnl Code: 0000001ecd281b8e: ec17ffff00d8 ahik %r1,%r7,-1 0000001ecd281b94: ec111dbc0355 risbg %r1,%r1,29,188,3 >0000001ecd281b9e: 94fb5006 ni 6(%r5),251 0000001ecd281ba2: 41505008 la %r5,8(%r5) 0000001ecd281ba6: ec51fffc6064 cgrj %r5,%r1,6,1ecd281b9e 0000001ecd281bac: 1a07 ar %r0,%r7 0000001ecd281bae: ec03ff584076 crj %r0,%r3,4,1ecd281a5e Call Trace: [<0000001ecd281b9e>] __kernel_map_pages+0x166/0x188 [<0000001ecd4d9516>] online_pages_range+0xf6/0x128 [<0000001ecd2a8186>] walk_system_ram_range+0x7e/0xd8 [<0000001ecda28aae>] online_pages+0x2fe/0x3f0 [<0000001ecd7d02a6>] memory_subsys_online+0x8e/0xc0 [<0000001ecd7add42>] device_online+0x5a/0xc8 [<0000001ecd7d0430>] state_store+0x88/0x118 [<0000001ecd5b9f62>] kernfs_fop_write+0xc2/0x200 [<0000001ecd5064b6>] vfs_write+0x176/0x1e0 [<0000001ecd50676a>] ksys_write+0xa2/0x100 [<0000001ecda315d4>] system_call+0xd8/0x2c8 Fix this by checking debug_pagealloc_enabled_static() before calling kernel_map_pages(). Backports for kernel before 5.5 should use debug_pagealloc_enabled() instead. Also add comments. Fixes: cd02cf1aceea ("mm/hotplug: fix an imbalance with DEBUG_PAGEALLOC") Reported-by: Gerald Schaefer Signed-off-by: Andrew Morton Signed-off-by: Vlastimil Babka Reviewed-by: David Hildenbrand Cc: Cc: Joonsoo Kim Cc: Qian Cai Link: http://lkml.kernel.org/r/20200224094651.18257-1-vbabka@suse.cz Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm, debug_pagealloc: don't rely on static keys too early

2020-01-23T07:22:40Z

commit 8e57f8acbbd121ecfb0c9dc13b8b030f86c6bd3b upstream. Commit 96a2b03f281d ("mm, debug_pagelloc: use static keys to enable debugging") has introduced a static key to reduce overhead when debug_pagealloc is compiled in but not enabled. It relied on the assumption that jump_label_init() is called before parse_early_param() as in start_kernel(), so when the "debug_pagealloc=on" option is parsed, it is safe to enable the static key. However, it turns out multiple architectures call parse_early_param() earlier from their setup_arch(). x86 also calls jump_label_init() even earlier, so no issue was found while testing the commit, but same is not true for e.g. ppc64 and s390 where the kernel would not boot with debug_pagealloc=on as found by our QA. To fix this without tricky changes to init code of multiple architectures, this patch partially reverts the static key conversion from 96a2b03f281d. Init-time and non-fastpath calls (such as in arch code) of debug_pagealloc_enabled() will again test a simple bool variable. Fastpath mm code is converted to a new debug_pagealloc_enabled_static() variant that relies on the static key, which is enabled in a well-defined point in mm_init() where it's guaranteed that jump_label_init() has been called, regardless of architecture. [sfr@canb.auug.org.au: export _debug_pagealloc_enabled_early] Link: http://lkml.kernel.org/r/20200106164944.063ac07b@canb.auug.org.au Link: http://lkml.kernel.org/r/20191219130612.23171-1-vbabka@suse.cz Fixes: 96a2b03f281d ("mm, debug_pagelloc: use static keys to enable debugging") Signed-off-by: Vlastimil Babka Signed-off-by: Stephen Rothwell Cc: Joonsoo Kim Cc: "Kirill A. Shutemov" Cc: Michal Hocko Cc: Vlastimil Babka Cc: Matthew Wilcox Cc: Mel Gorman Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Qian Cai Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: thp: handle page cache THP correctly in PageTransCompoundMap

2019-11-06T16:28:58Z

We have a usecase to use tmpfs as QEMU memory backend and we would like to take the advantage of THP as well. But, our test shows the EPT is not PMD mapped even though the underlying THP are PMD mapped on host. The number showed by /sys/kernel/debug/kvm/largepage is much less than the number of PMD mapped shmem pages as the below: 7f2778200000-7f2878200000 rw-s 00000000 00:14 262232 /dev/shm/qemu_back_mem.mem.Hz2hSf (deleted) Size: 4194304 kB [snip] AnonHugePages: 0 kB ShmemPmdMapped: 579584 kB [snip] Locked: 0 kB cat /sys/kernel/debug/kvm/largepages 12 And some benchmarks do worse than with anonymous THPs. By digging into the code we figured out that commit 127393fbe597 ("mm: thp: kvm: fix memory corruption in KVM with THP enabled") checks if there is a single PTE mapping on the page for anonymous THP when setting up EPT map. But the _mapcount < 0 check doesn't work for page cache THP since every subpage of page cache THP would get _mapcount inc'ed once it is PMD mapped, so PageTransCompoundMap() always returns false for page cache THP. This would prevent KVM from setting up PMD mapped EPT entry. So we need handle page cache THP correctly. However, when page cache THP's PMD gets split, kernel just remove the map instead of setting up PTE map like what anonymous THP does. Before KVM calls get_user_pages() the subpages may get PTE mapped even though it is still a THP since the page cache THP may be mapped by other processes at the mean time. Checking its _mapcount and whether the THP has PTE mapped or not. Although this may report some false negative cases (PTE mapped by other processes), it looks not trivial to make this accurate. With this fix /sys/kernel/debug/kvm/largepage would show reasonable pages are PMD mapped by EPT as the below: 7fbeaee00000-7fbfaee00000 rw-s 00000000 00:14 275464 /dev/shm/qemu_back_mem.mem.SKUvat (deleted) Size: 4194304 kB [snip] AnonHugePages: 0 kB ShmemPmdMapped: 557056 kB [snip] Locked: 0 kB cat /sys/kernel/debug/kvm/largepages 271 And the benchmarks are as same as anonymous THPs. [yang.shi@linux.alibaba.com: v4] Link: http://lkml.kernel.org/r/1571865575-42913-1-git-send-email-yang.shi@linux.alibaba.com Link: http://lkml.kernel.org/r/1571769577-89735-1-git-send-email-yang.shi@linux.alibaba.com Fixes: dd78fedde4b9 ("rmap: support file thp") Signed-off-by: Yang Shi Reported-by: Gang Deng Tested-by: Gang Deng Suggested-by: Hugh Dickins Acked-by: Kirill A. Shutemov Cc: Andrea Arcangeli Cc: Matthew Wilcox Cc: [4.8+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: treewide: clarify pgtable_page_{ctor,dtor}() naming

2019-09-26T17:10:44Z

The naming of pgtable_page_{ctor,dtor}() seems to have confused a few people, and until recently arm64 used these erroneously/pointlessly for other levels of page table. To make it incredibly clear that these only apply to the PTE level, and to align with the naming of pgtable_pmd_page_{ctor,dtor}(), let's rename them to pgtable_pte_page_{ctor,dtor}(). These changes were generated with the following shell script: ---- git grep -lw 'pgtable_page_.tor' | while read FILE; do sed -i '{s/pgtable_page_ctor/pgtable_pte_page_ctor/}' $FILE; sed -i '{s/pgtable_page_dtor/pgtable_pte_page_dtor/}' $FILE; done ---- ... with the documentation re-flowed to remain under 80 columns, and whitespace fixed up in macros to keep backslashes aligned. There should be no functional change as a result of this patch. Link: http://lkml.kernel.org/r/20190722141133.3116-1-mark.rutland@arm.com Signed-off-by: Mark Rutland Reviewed-by: Mike Rapoport Acked-by: Geert Uytterhoeven [m68k] Cc: Anshuman Khandual Cc: Matthew Wilcox Cc: Michal Hocko Cc: Yu Zhao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, fs: move randomize_stack_top from fs to mm

2019-09-24T22:54:11Z

Patch series "Provide generic top-down mmap layout functions", v6. This series introduces generic functions to make top-down mmap layout easily accessible to architectures, in particular riscv which was the initial goal of this series. The generic implementation was taken from arm64 and used successively by arm, mips and finally riscv. Note that in addition the series fixes 2 issues: - stack randomization was taken into account even if not necessary. - [1] fixed an issue with mmap base which did not take into account randomization but did not report it to arm and mips, so by moving arm64 into a generic library, this problem is now fixed for both architectures. This work is an effort to factorize architecture functions to avoid code duplication and oversights as in [1]. [1]: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html This patch (of 14): This preparatory commit moves this function so that further introduction of generic topdown mmap layout is contained only in mm/util.c. Link: http://lkml.kernel.org/r/20190730055113.23635-2-alex@ghiti.fr Signed-off-by: Alexandre Ghiti Acked-by: Kees Cook Reviewed-by: Christoph Hellwig Reviewed-by: Luis Chamberlain Cc: Russell King Cc: Catalin Marinas Cc: Will Deacon Cc: Ralf Baechle Cc: Paul Burton Cc: James Hogan Cc: Palmer Dabbelt Cc: Albert Ou Cc: Alexander Viro Cc: Christoph Hellwig Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, thp: introduce FOLL_SPLIT_PMD

2019-09-24T22:54:11Z

Introduce a new foll_flag: FOLL_SPLIT_PMD. As the name says FOLL_SPLIT_PMD splits huge pmd for given mm_struct, the underlining huge page stays as-is. FOLL_SPLIT_PMD is useful for cases where we need to use regular pages, but would switch back to huge page and huge pmd on. One of such example is uprobe. The following patches use FOLL_SPLIT_PMD in uprobe. Link: http://lkml.kernel.org/r/20190815164525.1848545-4-songliubraving@fb.com Signed-off-by: Song Liu Reviewed-by: Oleg Nesterov Acked-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: move memcmp_pages() and pages_identical()

2019-09-24T22:54:11Z

Patch series "THP aware uprobe", v13. This patchset makes uprobe aware of THPs. Currently, when uprobe is attached to text on THP, the page is split by FOLL_SPLIT. As a result, uprobe eliminates the performance benefit of THP. This set makes uprobe THP-aware. Instead of FOLL_SPLIT, we introduces FOLL_SPLIT_PMD, which only split PMD for uprobe. After all uprobes within the THP are removed, the PTE-mapped pages are regrouped as huge PMD. This set (plus a few THP patches) is also available at https://github.com/liu-song-6/linux/tree/uprobe-thp This patch (of 6): Move memcmp_pages() to mm/util.c and pages_identical() to mm.h, so that we can use them in other files. Link: http://lkml.kernel.org/r/20190815164525.1848545-2-songliubraving@fb.com Signed-off-by: Song Liu Acked-by: Kirill A. Shutemov Reviewed-by: Oleg Nesterov Cc: Johannes Weiner Cc: Matthew Wilcox Cc: William Kucharski Cc: Srikar Dronamraju Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/gup: add make_dirty arg to put_user_pages_dirty_lock()

2019-09-24T22:54:08Z

[11~From: John Hubbard Subject: mm/gup: add make_dirty arg to put_user_pages_dirty_lock() Patch series "mm/gup: add make_dirty arg to put_user_pages_dirty_lock()", v3. There are about 50+ patches in my tree [2], and I'll be sending out the remaining ones in a few more groups: * The block/bio related changes (Jerome mostly wrote those, but I've had to move stuff around extensively, and add a little code) * mm/ changes * other subsystem patches * an RFC that shows the current state of the tracking patch set. That can only be applied after all call sites are converted, but it's good to get an early look at it. This is part a tree-wide conversion, as described in fc1d8e7cca2d ("mm: introduce put_user_page*(), placeholder versions"). This patch (of 3): Provide more capable variation of put_user_pages_dirty_lock(), and delete put_user_pages_dirty(). This is based on the following: 1. Lots of call sites become simpler if a bool is passed into put_user_page*(), instead of making the call site choose which put_user_page*() variant to call. 2. Christoph Hellwig's observation that set_page_dirty_lock() is usually correct, and set_page_dirty() is usually a bug, or at least questionable, within a put_user_page*() calling chain. This leads to the following API choices: * put_user_pages_dirty_lock(page, npages, make_dirty) * There is no put_user_pages_dirty(). You have to hand code that, in the rare case that it's required. [jhubbard@nvidia.com: remove unused variable in siw_free_plist()] Link: http://lkml.kernel.org/r/20190729074306.10368-1-jhubbard@nvidia.com Link: http://lkml.kernel.org/r/20190724044537.10458-2-jhubbard@nvidia.com Signed-off-by: John Hubbard Cc: Matthew Wilcox Cc: Jan Kara Cc: Christoph Hellwig Cc: Ira Weiny Cc: Jason Gunthorpe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds