Messages in this thread | | | Date | Fri, 1 Dec 2017 13:18:32 +0000 | From | Will Deacon <> | Subject | Re: a racy access flag clearing warning when calling mmap system call |
| |
On Fri, Dec 01, 2017 at 03:38:04PM +0800, chenjiankang wrote: > I find a warning by a syzkaller test; > > When the mmap syscall is called to create a virtual memory, > firstly it delete a old huge page mapping area; > Before splitting the huge page, the pmd of a huge page is set up. > But The PTE_AF is zreo belonging to the current pmd of huge page. > I suspect that when the child process is created, the PTE_AF is cleared in copy_one_pte(); > So, the set_pte_at() can have a warning. > > There, whether the set_pte_at() should detect PTE_AF? > > Thanks. > > The log: > > set_pte_at: racy access flag clearing: 00e000009d200bd1 -> 01e000009d200bd1 > ------------[ cut here ]------------ > WARNING: at ../../../../../kernel/linux-4.1/arch/arm64/include/asm/pgtable.h:211
Given that this is a fairly old 4.1 kernel, could you try to reproduce the failure with something more recent, please? We've fixed many bugs since then, some of them involving huge pages.
Thanks,
Will
> Modules linked in: > CPU: 0 PID: 3665 Comm: syz-executor7 Not tainted 4.1.44+ #1 > Hardware name: linux,dummy-virt (DT) > task: ffffffc06a873fc0 ti: ffffffc05aefc000 task.ti: ffffffc05aefc000 > PC is at pmdp_splitting_flush+0x194/0x1b0 > LR is at pmdp_splitting_flush+0x194/0x1b0 > pc : [<ffffffc0000a5244>] lr : [<ffffffc0000a5244>] pstate: 80000145 > sp : ffffffc05aeff770 > x29: ffffffc05aeff770 x28: ffffffc05ae45800 > x27: 0000000020200000 x26: ffffffc061fdf450 > x25: 0000000000020000 x24: 0000000000000001 > x23: ffffffc06333d9c8 x22: ffffffc0014ba000 > x21: 01e000009d200bd1 x20: 00e000009d200bd1 > x19: ffffffc05ae45800 x18: 0000000000000000 > x17: 00000000004b4000 x16: ffffffc00017fdc0 > x15: 00000000038ee280 x14: 3030653130203e2d > x13: 2031646230303264 x12: 3930303030306530 > x11: 30203a676e697261 x10: 656c632067616c66 > x9 : 2073736563636120 x8 : 79636172203a7461 > x7 : ffffffc05aeff430 x6 : ffffffc00015f38c > x5 : 0000000000000003 x4 : 0000000000000000 > x3 : 0000000000000003 x2 : 0000000000010000 > x1 : ffffff9005a03000 x0 : 000000000000004b > Call trace: > [<ffffffc0000a5244>] pmdp_splitting_flush+0x194/0x1b0 > [<ffffffc0002784c0>] split_huge_page_to_list+0x168/0xdb0 > [<ffffffc00027a0d8>] __split_huge_page_pmd+0x1b0/0x510 > [<ffffffc00027b5ac>] split_huge_page_pmd_mm+0x84/0x88 > [<ffffffc00027b674>] split_huge_page_address+0xc4/0xe8 > [<ffffffc00027b7f4>] __vma_adjust_trans_huge+0x15c/0x190 > [<ffffffc000238d5c>] vma_adjust+0x884/0x9f0 > [<ffffffc0002390c8>] __split_vma.isra.5+0x200/0x310 > [<ffffffc00023b7b8>] do_munmap+0x5e0/0x608 > [<ffffffc00023c0d4>] mmap_region+0x12c/0x900 > [<ffffffc00023cd2c>] do_mmap_pgoff+0x484/0x540 > [<ffffffc000218118>] vm_mmap_pgoff+0x128/0x158 > [<ffffffc000239920>] SyS_mmap_pgoff+0x188/0x300 > [<ffffffc00008cce0>] sys_mmap+0x58/0x80 >
| |