On Tue, Jan 26, 2016 at 01:52:31PM +0100, Dmitry Vyukov wrote: > Hello, > > The following program triggers the following bug: > > page:ffffea0000b82240 count:0 mapcount:1 mapping:dead0000ffffffff > index:0x0 compound_mapcount: 0 > flags: 0x1fffc0000000000() > page dumped because: VM_BUG_ON_PAGE(PageTail(page)) > ------------[ cut here ]------------ > kernel BUG at mm/vmscan.c:1446! > invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN > Modules linked in: > CPU: 1 PID: 6868 Comm: a.out Not tainted 4.5.0-rc1+ #287 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > task: ffff88003e24af80 ti: ffff88002e808000 task.ti: ffff88002e808000 > RIP: 0010:[<ffffffff816a4b7a>] [<ffffffff816a4b7a>] > isolate_lru_page+0x4ea/0x6d0 > RSP: 0018:ffff88002e80fa50 EFLAGS: 00010282 > RAX: ffff88003e24af80 RBX: ffffea0000b82240 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffea0000b82278 > RBP: ffff88002e80fa88 R08: 0000000000000001 R09: 0000000000000000 > R10: ffff88003e24af80 R11: 0000000000000001 R12: ffffea0000b82260 > R13: ffffea0000b82200 R14: ffffea0000b82201 R15: 0000000020004000 > FS: 0000000000c1f880(0063) GS:ffff88003ed00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > CR2: 0000000020005ff8 CR3: 000000002e324000 CR4: 00000000000006e0 > Stack: > dffffc0000000000 ffffffff816f5e89 ffff88003124b010 0000000020002000 > dffffc0000000000 ffffea0000b82240 0000000020004000 ffff88002e80fb10 > ffffffff817612bd ffffea0000000001 ffff88002e80fc70 ffff88002e80fde8 > Call Trace: > [< inline >] migrate_page_add mm/mempolicy.c:966 > [<ffffffff817612bd>] queue_pages_pte_range+0x4ad/0x10b0 mm/mempolicy.c:552 > [< inline >] walk_pmd_range mm/pagewalk.c:50 > [< inline >] walk_pud_range mm/pagewalk.c:90 > [< inline >] walk_pgd_range mm/pagewalk.c:116 > [<ffffffff81732713>] __walk_page_range+0x653/0xcd0 mm/pagewalk.c:204 > [<ffffffff81732ec4>] walk_page_range+0x134/0x300 mm/pagewalk.c:281 > [<ffffffff8175f07b>] queue_pages_range+0xfb/0x130 mm/mempolicy.c:687 > [<ffffffff817678c1>] do_mbind+0x2c1/0xdc0 mm/mempolicy.c:1239 > [< inline >] SYSC_mbind mm/mempolicy.c:1351 > [<ffffffff8176871d>] SyS_mbind+0x13d/0x150 mm/mempolicy.c:1333 > [<ffffffff8646ed76>] entry_SYSCALL_64_fastpath+0x16/0x7a > arch/x86/entry/entry_64.S:185 > Code: 89 df e8 aa 64 04 00 0f 0b e8 63 6d ed ff 4d 8d 6e ff e9 73 fb > ff ff e8 55 6d ed ff 48 c7 c6 60 7b 5b 86 48 89 df e8 86 64 04 00 <0f> > 0b e8 3f 6d ed ff 4d 8d 6e ff e9 eb fb ff ff c7 45 d0 f0 ff > RIP [<ffffffff816a4b7a>] isolate_lru_page+0x4ea/0x6d0 mm/vmscan.c:1446 > RSP <ffff88002e80fa50> > ---[ end trace 310d844ac0b69c5b ]--- > BUG: sleeping function called from invalid context at include/linux/sched.h:2805 > in_atomic(): 1, irqs_disabled(): 0, pid: 6868, name: a.out > INFO: lockdep is turned off. > CPU: 1 PID: 6868 Comm: a.out Tainted: G D 4.5.0-rc1+ #287 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > 00000000ffffffff ffff88002e80f548 ffffffff829f9d0d ffff88003e24af80 > 0000000000001ad4 0000000000000000 ffff88002e80f570 ffffffff813cba2b > ffff88003e24af80 ffffffff865527a0 0000000000000af5 ffff88002e80f5b0 > Call Trace: > [< inline >] __dump_stack lib/dump_stack.c:15 > [<ffffffff829f9d0d>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 > [<ffffffff813cba2b>] ___might_sleep+0x27b/0x3a0 kernel/sched/core.c:7703 > [<ffffffff813cbbe0>] __might_sleep+0x90/0x1a0 kernel/sched/core.c:7665 > [< inline >] threadgroup_change_begin include/linux/sched.h:2805 > [<ffffffff81383221>] exit_signals+0x81/0x430 kernel/signal.c:2392 > [<ffffffff8135c55c>] do_exit+0x23c/0x2cb0 kernel/exit.c:701 > [<ffffffff811aa28f>] oops_end+0x9f/0xd0 arch/x86/kernel/dumpstack.c:250 > [<ffffffff811aa686>] die+0x46/0x60 arch/x86/kernel/dumpstack.c:316 > [< inline >] do_trap_no_signal arch/x86/kernel/traps.c:205 > [<ffffffff811a3b9f>] do_trap+0x18f/0x380 arch/x86/kernel/traps.c:251 > [<ffffffff811a400e>] do_error_trap+0x11e/0x280 arch/x86/kernel/traps.c:290 > [<ffffffff811a527b>] do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:303 > [<ffffffff86470a8e>] invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:830 > [< inline >] migrate_page_add mm/mempolicy.c:966 > [<ffffffff817612bd>] queue_pages_pte_range+0x4ad/0x10b0 mm/mempolicy.c:552 > [< inline >] walk_pmd_range mm/pagewalk.c:50 > [< inline >] walk_pud_range mm/pagewalk.c:90 > [< inline >] walk_pgd_range mm/pagewalk.c:116 > [<ffffffff81732713>] __walk_page_range+0x653/0xcd0 mm/pagewalk.c:204 > [<ffffffff81732ec4>] walk_page_range+0x134/0x300 mm/pagewalk.c:281 > [<ffffffff8175f07b>] queue_pages_range+0xfb/0x130 mm/mempolicy.c:687 > [<ffffffff817678c1>] do_mbind+0x2c1/0xdc0 mm/mempolicy.c:1239 > [< inline >] SYSC_mbind mm/mempolicy.c:1351 > [<ffffffff8176871d>] SyS_mbind+0x13d/0x150 mm/mempolicy.c:1333 > [<ffffffff8646ed76>] entry_SYSCALL_64_fastpath+0x16/0x7a > arch/x86/entry/entry_64.S:185 > note: a.out[6868] exited with preempt_count 1 > > > // autogenerated by syzkaller (http://github.com/google/syzkaller) > #include <pthread.h> > #include <stdint.h> > #include <string.h> > #include <sys/syscall.h> > #include <unistd.h> > #include <fcntl.h> > > #ifndef SYS_mlock2 > #define SYS_mlock2 325 > #endif > > int main() > { > long r[8]; > memset(r, -1, sizeof(r)); > r[0] = syscall(SYS_mmap, 0x20000000ul, 0x1000ul, 0x3ul, 0x32ul, > 0xfffffffffffffffful, 0x0ul); > memcpy((void*)0x20000f33, "\x2f\x64\x65\x76\x2f\x73\x67\x23", 8); > r[2] = syscall(SYS_open, "/dev/sg0",O_RDWR); > r[3] = syscall(SYS_mmap, 0x20001000ul, 0x4000ul, 0x4ul, 0x12ul, r[2], > 0x0ul); > r[4] = syscall(SYS_mlock2, 0x20001000ul, 0x3000ul, 0x1ul, 0, 0, 0); > r[5] = syscall(SYS_mmap, 0x20005000ul, 0x1000ul, 0x3ul, 0x32ul, > 0xfffffffffffffffful, 0x0ul); > *(uint64_t*)0x20005ff8 = (uint64_t)0x80000000; > r[7] = syscall(SYS_mbind, 0x20000000ul, 0x4000ul, 0x8000ul, > 0x20005ff8ul, 0x5ul, 0x2ul); > return 0; > } > > > On commit 92e963f50fc74041b5e9e744c330dca48e04f08d. The patch below fixes the issue for me, but this bug makes me wounder how many bugs like this we have in kernel... :-/ Looks like we are too permissive about which VMA is migratable: vma_migratable() filters out VMA by VM_IO and VM_PFNMAP. I think VM_DONTEXPAND also correlate with VMA which cannot be migrated. $ git grep VM_DONTEXPAND drivers | grep -v '\(VM_IO\|VM_PFNMAN\)' | wc -l 33 Hm.. :-| It worth looking on them closely... And I wouldn't be surprised if some VMAs without all of these flags are not migratable too. Sigh.. Any thoughts? >From 396ad132be07a2d2b9ec5d1d6ec9fe2fffe8105e Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Date: Tue, 26 Jan 2016 22:59:16 +0300 Subject: [PATCH] sg: mark VMA as VM_IO to prevent migration Reduced testcase: #include <fcntl.h> #include <unistd.h> #include <sys/mman.h> #include <numaif.h> #define SIZE 0x2000 int main() { int fd; void *p; fd = open("/dev/sg0", O_RDWR); p = mmap(NULL, SIZE, PROT_EXEC, MAP_PRIVATE | MAP_LOCKED, fd, 0); mbind(p, SIZE, 0, NULL, 0, MPOL_MF_MOVE); return 0; } We shouldn't try to migrate pages in sg VMA as we don't have a way to update Sg_scatter_hold::pages accordingly from mm core. Let's mark the VMA as VM_IO to indicate to mm core that the VMA is migratable. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> --- drivers/scsi/sg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 503ab8b46c0b..5e820674432c 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1261,7 +1261,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma) } sfp->mmap_called = 1; - vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP; + vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP; vma->vm_private_data = sfp; vma->vm_ops = &sg_mmap_vm_ops; return 0; -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>