* [syzbot] WARNING in __split_huge_page_tail @ 2022-10-26 6:59 syzbot 2022-10-26 9:54 ` David Hildenbrand 0 siblings, 1 reply; 6+ messages in thread From: syzbot @ 2022-10-26 6:59 UTC (permalink / raw) To: akpm, linux-kernel, linux-mm, syzkaller-bugs Hello, syzbot found the following issue on: HEAD commit: 4da34b7d175d Merge tag 'thermal-6.1-rc2' of git://git.kern.. git tree: upstream console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000 kernel config: https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57 dashboard link: https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+273b547b15eb58ea35e8@syzkaller.appspotmail.com tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363 exit_mmap+0x2b1/0x670 mm/mmap.c:3098 __mmput+0x114/0x3b0 kernel/fork.c:1185 exit_mm+0x217/0x2f0 kernel/exit.c:516 do_exit+0x5e7/0x2070 kernel/exit.c:807 do_group_exit+0x1fd/0x2b0 kernel/exit.c:950 __do_sys_exit_group kernel/exit.c:961 [inline] __se_sys_exit_group kernel/exit.c:959 [inline] __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd ------------[ cut here ]------------ WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 Modules linked in: CPU: 0 PID: 3908 Comm: syz-executor315 Not tainted 6.1.0-rc1-syzkaller-00249-g4da34b7d175d #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 RIP: 0010:__split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 Code: ff ff e8 57 a7 a6 ff 48 ff cb e9 1a fd ff ff e8 4a a7 a6 ff 4c 89 ef 48 c7 c6 80 5d bb 8a e8 6b f0 e3 ff c6 05 2f 20 30 0c 01 <0f> 0b e9 cb fb ff ff 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c 29 f8 ff RSP: 0018:ffffc900044b6ba8 EFLAGS: 00010046 RAX: beb4e3f6a4108300 RBX: 1ffffd400031ed85 RCX: ffffffff8169255b RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e277d28 RBP: ffffea00018f0008 R08: dffffc0000000000 R09: fffffbfff1c4efa6 R10: fffffbfff1c4efa6 R11: 1ffffffff1c4efa5 R12: ffffea00018f6c00 R13: ffffea00018f0000 R14: 1ffffd400031e001 R15: ffffea00018f6c28 FS: 00005555567b0300(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020001304 CR3: 000000001d5c1000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __split_huge_page+0x403/0x1df0 mm/huge_memory.c:2527 split_huge_page_to_list+0x101d/0x1c90 mm/huge_memory.c:2756 split_huge_page include/linux/huge_mm.h:188 [inline] deferred_split_scan+0x683/0x8b0 mm/huge_memory.c:2882 do_shrink_slab+0x4e1/0xa00 mm/vmscan.c:842 shrink_slab_memcg+0x2ec/0x630 mm/vmscan.c:911 shrink_slab+0xbe/0x340 mm/vmscan.c:990 shrink_node_memcgs+0x3c3/0x770 mm/vmscan.c:6076 shrink_node+0x299/0x1050 mm/vmscan.c:6105 shrink_zones+0x4fb/0xc40 mm/vmscan.c:6343 do_try_to_free_pages+0x215/0xcd0 mm/vmscan.c:6405 try_to_free_mem_cgroup_pages+0x3cb/0x6d0 mm/vmscan.c:6720 try_charge_memcg+0x6a1/0x11f0 mm/memcontrol.c:2681 try_charge mm/memcontrol.c:2823 [inline] mem_cgroup_charge_skmem+0xa7/0x370 mm/memcontrol.c:7209 sock_reserve_memory+0x105/0x640 net/core/sock.c:1018 sk_setsockopt+0x16bf/0x32c0 net/core/sock.c:1518 __sys_setsockopt+0x6ba/0xa00 net/socket.c:2248 __do_sys_setsockopt net/socket.c:2263 [inline] __se_sys_setsockopt net/socket.c:2260 [inline] __x64_sys_setsockopt+0xb1/0xc0 net/socket.c:2260 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7ff3a2ea8ee9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd09efcd08 EFLAGS: 00000246 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007ff3a2ea8ee9 RDX: 0000000000000049 RSI: 0000000000000001 RDI: 0000000000000004 RBP: 0000000000000000 R08: 0000000000000010 R09: 00007ffd09efcd30 R10: 0000000020000040 R11: 0000000000000246 R12: 00007ffd09efcd2c R13: 00007ffd09efcd40 R14: 00007ffd09efcd80 R15: 0000000000000130 </TASK> --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING in __split_huge_page_tail 2022-10-26 6:59 [syzbot] WARNING in __split_huge_page_tail syzbot @ 2022-10-26 9:54 ` David Hildenbrand 2022-10-26 13:25 ` Dmitry Vyukov 0 siblings, 1 reply; 6+ messages in thread From: David Hildenbrand @ 2022-10-26 9:54 UTC (permalink / raw) To: syzbot, akpm, linux-kernel, linux-mm, syzkaller-bugs On 26.10.22 08:59, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 4da34b7d175d Merge tag 'thermal-6.1-rc2' of git://git.kern.. > git tree: upstream > console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000 > kernel config: https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57 > dashboard link: https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+273b547b15eb58ea35e8@syzkaller.appspotmail.com > > tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363 > exit_mmap+0x2b1/0x670 mm/mmap.c:3098 > __mmput+0x114/0x3b0 kernel/fork.c:1185 > exit_mm+0x217/0x2f0 kernel/exit.c:516 > do_exit+0x5e7/0x2070 kernel/exit.c:807 > do_group_exit+0x1fd/0x2b0 kernel/exit.c:950 > __do_sys_exit_group kernel/exit.c:961 [inline] > __se_sys_exit_group kernel/exit.c:959 [inline] > __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 Is this the VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); assertion? -- Thanks, David / dhildenb ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING in __split_huge_page_tail 2022-10-26 9:54 ` David Hildenbrand @ 2022-10-26 13:25 ` Dmitry Vyukov 2022-10-26 14:46 ` David Hildenbrand 0 siblings, 1 reply; 6+ messages in thread From: Dmitry Vyukov @ 2022-10-26 13:25 UTC (permalink / raw) To: David Hildenbrand; +Cc: syzbot, akpm, linux-kernel, linux-mm, syzkaller-bugs On Wed, 26 Oct 2022 at 02:54, David Hildenbrand <david@redhat.com> wrote: > > On 26.10.22 08:59, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 4da34b7d175d Merge tag 'thermal-6.1-rc2' of git://git.kern.. > > git tree: upstream > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57 > > dashboard link: https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > > compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000 > > > > Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+273b547b15eb58ea35e8@syzkaller.appspotmail.com > > > > tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363 > > exit_mmap+0x2b1/0x670 mm/mmap.c:3098 > > __mmput+0x114/0x3b0 kernel/fork.c:1185 > > exit_mm+0x217/0x2f0 kernel/exit.c:516 > > do_exit+0x5e7/0x2070 kernel/exit.c:807 > > do_group_exit+0x1fd/0x2b0 kernel/exit.c:950 > > __do_sys_exit_group kernel/exit.c:961 [inline] > > __se_sys_exit_group kernel/exit.c:959 [inline] > > __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > ------------[ cut here ]------------ > > WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 > > Is this the > > VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); > > assertion? Hi David, You can check the sources for that revision, but on the dashboard there are clickable links for all source references: https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 In this case it points to: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/huge_memory.c?id=4da34b7d175dc99b8befebd69e96546c960d526c#n2465 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING in __split_huge_page_tail 2022-10-26 13:25 ` Dmitry Vyukov @ 2022-10-26 14:46 ` David Hildenbrand 2022-10-26 16:17 ` Hugh Dickins 0 siblings, 1 reply; 6+ messages in thread From: David Hildenbrand @ 2022-10-26 14:46 UTC (permalink / raw) To: Dmitry Vyukov Cc: syzbot, akpm, linux-kernel, linux-mm, syzkaller-bugs, Mel Gorman, Hugh Dickins On 26.10.22 15:25, Dmitry Vyukov wrote: > On Wed, 26 Oct 2022 at 02:54, David Hildenbrand <david@redhat.com> wrote: >> >> On 26.10.22 08:59, syzbot wrote: >>> Hello, >>> >>> syzbot found the following issue on: >>> >>> HEAD commit: 4da34b7d175d Merge tag 'thermal-6.1-rc2' of git://git.kern.. >>> git tree: upstream >>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000 >>> kernel config: https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57 >>> dashboard link: https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 >>> compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000 >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000 >>> >>> Downloadable assets: >>> disk image: https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz >>> vmlinux: https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz >>> >>> IMPORTANT: if you fix the issue, please add the following tag to the commit: >>> Reported-by: syzbot+273b547b15eb58ea35e8@syzkaller.appspotmail.com >>> >>> tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363 >>> exit_mmap+0x2b1/0x670 mm/mmap.c:3098 >>> __mmput+0x114/0x3b0 kernel/fork.c:1185 >>> exit_mm+0x217/0x2f0 kernel/exit.c:516 >>> do_exit+0x5e7/0x2070 kernel/exit.c:807 >>> do_group_exit+0x1fd/0x2b0 kernel/exit.c:950 >>> __do_sys_exit_group kernel/exit.c:961 [inline] >>> __se_sys_exit_group kernel/exit.c:959 [inline] >>> __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959 >>> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >>> do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 >>> entry_SYSCALL_64_after_hwframe+0x63/0xcd >>> ------------[ cut here ]------------ >>> WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 >> >> Is this the >> >> VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); >> >> assertion? > > Hi David, > > You can check the sources for that revision, but on the dashboard > there are clickable links for all source references: > https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > > In this case it points to: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/huge_memory.c?id=4da34b7d175dc99b8befebd69e96546c960d526c#n2465 > Ah, thanks! ... so if (!folio_test_swapcache(page_folio(head))) { VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); page_tail->private = 0; } I recall that there was a patch either from Hugh or Mel floating around that might be related. -- Thanks, David / dhildenb ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING in __split_huge_page_tail 2022-10-26 14:46 ` David Hildenbrand @ 2022-10-26 16:17 ` Hugh Dickins 2022-11-13 16:44 ` Dmitry Vyukov 0 siblings, 1 reply; 6+ messages in thread From: Hugh Dickins @ 2022-10-26 16:17 UTC (permalink / raw) To: David Hildenbrand Cc: Dmitry Vyukov, syzbot, akpm, linux-kernel, linux-mm, syzkaller-bugs, Mel Gorman, Hugh Dickins On Wed, 26 Oct 2022, David Hildenbrand wrote: > On 26.10.22 15:25, Dmitry Vyukov wrote: > > On Wed, 26 Oct 2022 at 02:54, David Hildenbrand <david@redhat.com> wrote: > >> On 26.10.22 08:59, syzbot wrote: > >>> Hello, > >>> > >>> syzbot found the following issue on: > >>> > >>> HEAD commit: 4da34b7d175d Merge tag 'thermal-6.1-rc2' of > >>> git://git.kern.. > >>> git tree: upstream > >>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000 > >>> kernel config: https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57 > >>> dashboard link: > >>> https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > >>> compiler: Debian clang version > >>> 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU > >>> Binutils for Debian) 2.35.2 > >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000 > >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000 > >>> > >>> Downloadable assets: > >>> disk image: > >>> https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz > >>> vmlinux: > >>> https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz > >>> > >>> IMPORTANT: if you fix the issue, please add the following tag to the > >>> commit: > >>> Reported-by: syzbot+273b547b15eb58ea35e8@syzkaller.appspotmail.com > >>> > >>> tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363 > >>> exit_mmap+0x2b1/0x670 mm/mmap.c:3098 > >>> __mmput+0x114/0x3b0 kernel/fork.c:1185 > >>> exit_mm+0x217/0x2f0 kernel/exit.c:516 > >>> do_exit+0x5e7/0x2070 kernel/exit.c:807 > >>> do_group_exit+0x1fd/0x2b0 kernel/exit.c:950 > >>> __do_sys_exit_group kernel/exit.c:961 [inline] > >>> __se_sys_exit_group kernel/exit.c:959 [inline] > >>> __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959 > >>> do_syscall_x64 arch/x86/entry/common.c:50 [inline] > >>> do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 > >>> entry_SYSCALL_64_after_hwframe+0x63/0xcd > >>> ------------[ cut here ]------------ > >>> WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 > >>> __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 > >> > >> Is this the > >> > >> VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); > >> > >> assertion? > > > > Hi David, > > > > You can check the sources for that revision, but on the dashboard > > there are clickable links for all source references: > > https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > > > > In this case it points to: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/huge_memory.c?id=4da34b7d175dc99b8befebd69e96546c960d526c#n2465 > > > > Ah, thanks! > > ... so > > if (!folio_test_swapcache(page_folio(head))) { > VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); > page_tail->private = 0; > } > > I recall that there was a patch either from Hugh or Mel floating around that > might be related. Yes, it's in akpm's mm-hotfixes-unstable branch, currently at 826367c8c422 ("mm: prep_compound_tail() clear page->private") [PATCH] mm: prep_compound_tail() clear page->private Although page allocation always clears page->private in the first page or head page of an allocation, it has never made a point of clearing page->private in the tails (though 0 is often what is already there). But now commit 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") issues a warning when page_tail->private is found to be non-0 (unless it's swapcache). Change that warning to dump page_tail (which also dumps head), instead of just the head: so far we have seen dead000000000122, dead000000000003, dead000000000001 or 0000000000000002 in the raw output for tail private. We could just delete the warning, but today's consensus appears to want page->private to be 0, unless there's a good reason for it to be set: so now clear it in prep_compound_tail() (more general than just for THP; but not for high order allocation, which makes no pass down the tails). Fixes: 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: <stable@vger.kernel.org> --- mm/huge_memory.c | 2 +- mm/page_alloc.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 03fc7e5edf07..561a42567477 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2462,7 +2462,7 @@ static void __split_huge_page_tail(struct page *head, int tail, * Fix up and warn once if private is unexpectedly set. */ if (!folio_test_swapcache(page_folio(head))) { - VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); + VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail); page_tail->private = 0; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b5a6c815ae28..218b28ee49ed 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -807,6 +807,7 @@ static void prep_compound_tail(struct page *head, int tail_idx) p->mapping = TAIL_MAPPING; set_compound_head(p, head); + set_page_private(p, 0); } void prep_compound_page(struct page *page, unsigned int order) -- 2.35.3 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING in __split_huge_page_tail 2022-10-26 16:17 ` Hugh Dickins @ 2022-11-13 16:44 ` Dmitry Vyukov 0 siblings, 0 replies; 6+ messages in thread From: Dmitry Vyukov @ 2022-11-13 16:44 UTC (permalink / raw) To: Hugh Dickins Cc: David Hildenbrand, syzbot, akpm, linux-kernel, linux-mm, syzkaller-bugs, Mel Gorman On Wed, 26 Oct 2022 at 18:18, Hugh Dickins <hughd@google.com> wrote: > > >> On 26.10.22 08:59, syzbot wrote: > > >>> Hello, > > >>> > > >>> syzbot found the following issue on: > > >>> > > >>> HEAD commit: 4da34b7d175d Merge tag 'thermal-6.1-rc2' of > > >>> git://git.kern.. > > >>> git tree: upstream > > >>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000 > > >>> kernel config: https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57 > > >>> dashboard link: > > >>> https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > > >>> compiler: Debian clang version > > >>> 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU > > >>> Binutils for Debian) 2.35.2 > > >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000 > > >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000 > > >>> > > >>> Downloadable assets: > > >>> disk image: > > >>> https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz > > >>> vmlinux: > > >>> https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz > > >>> > > >>> IMPORTANT: if you fix the issue, please add the following tag to the > > >>> commit: > > >>> Reported-by: syzbot+273b547b15eb58ea35e8@syzkaller.appspotmail.com > > >>> > > >>> tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363 > > >>> exit_mmap+0x2b1/0x670 mm/mmap.c:3098 > > >>> __mmput+0x114/0x3b0 kernel/fork.c:1185 > > >>> exit_mm+0x217/0x2f0 kernel/exit.c:516 > > >>> do_exit+0x5e7/0x2070 kernel/exit.c:807 > > >>> do_group_exit+0x1fd/0x2b0 kernel/exit.c:950 > > >>> __do_sys_exit_group kernel/exit.c:961 [inline] > > >>> __se_sys_exit_group kernel/exit.c:959 [inline] > > >>> __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959 > > >>> do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > >>> do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 > > >>> entry_SYSCALL_64_after_hwframe+0x63/0xcd > > >>> ------------[ cut here ]------------ > > >>> WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 > > >>> __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 > > >> > > >> Is this the > > >> > > >> VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); > > >> > > >> assertion? > > > > > > Hi David, > > > > > > You can check the sources for that revision, but on the dashboard > > > there are clickable links for all source references: > > > https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > > > > > > In this case it points to: > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/huge_memory.c?id=4da34b7d175dc99b8befebd69e96546c960d526c#n2465 > > > > > > > Ah, thanks! > > > > ... so > > > > if (!folio_test_swapcache(page_folio(head))) { > > VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); > > page_tail->private = 0; > > } > > > > I recall that there was a patch either from Hugh or Mel floating around that > > might be related. > > Yes, it's in akpm's mm-hotfixes-unstable branch, currently at > 826367c8c422 ("mm: prep_compound_tail() clear page->private") Let's tell syzbot about the fix so that it reports similar bugs in future: #syz fix: mm: prep_compound_tail() clear page->private > [PATCH] mm: prep_compound_tail() clear page->private > > Although page allocation always clears page->private in the first page > or head page of an allocation, it has never made a point of clearing > page->private in the tails (though 0 is often what is already there). > > But now commit 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t > during THP split") issues a warning when page_tail->private is found to > be non-0 (unless it's swapcache). > > Change that warning to dump page_tail (which also dumps head), instead > of just the head: so far we have seen dead000000000122, dead000000000003, > dead000000000001 or 0000000000000002 in the raw output for tail private. > > We could just delete the warning, but today's consensus appears to want > page->private to be 0, unless there's a good reason for it to be set: > so now clear it in prep_compound_tail() (more general than just for THP; > but not for high order allocation, which makes no pass down the tails). > > Fixes: 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") > Signed-off-by: Hugh Dickins <hughd@google.com> > Cc: Mel Gorman <mgorman@techsingularity.net> > Cc: Matthew Wilcox (Oracle) <willy@infradead.org> > Cc: <stable@vger.kernel.org> > --- > mm/huge_memory.c | 2 +- > mm/page_alloc.c | 1 + > 2 files changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 03fc7e5edf07..561a42567477 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2462,7 +2462,7 @@ static void __split_huge_page_tail(struct page *head, int tail, > * Fix up and warn once if private is unexpectedly set. > */ > if (!folio_test_swapcache(page_folio(head))) { > - VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); > + VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail); > page_tail->private = 0; > } > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index b5a6c815ae28..218b28ee49ed 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -807,6 +807,7 @@ static void prep_compound_tail(struct page *head, int tail_idx) > > p->mapping = TAIL_MAPPING; > set_compound_head(p, head); > + set_page_private(p, 0); > } > > void prep_compound_page(struct page *page, unsigned int order) > -- > 2.35.3 ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-11-13 16:44 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-10-26 6:59 [syzbot] WARNING in __split_huge_page_tail syzbot 2022-10-26 9:54 ` David Hildenbrand 2022-10-26 13:25 ` Dmitry Vyukov 2022-10-26 14:46 ` David Hildenbrand 2022-10-26 16:17 ` Hugh Dickins 2022-11-13 16:44 ` Dmitry Vyukov
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