From: Andrea Arcangeli <aarcange@xxxxxxxxxx> Subject: userfaultfd: hugetlbfs: remove superfluous page unlock in VM_SHARED case huge_add_to_page_cache->add_to_page_cache implicitly unlocks the page before returning in case of errors. The error returned was -EEXIST by running UFFDIO_COPY on a non-hole offset of a VM_SHARED hugetlbfs mapping. It was an userland bug that triggered it and the kernel must cope with it returning -EEXIST from ioctl(UFFDIO_COPY) as expected. page dumped because: VM_BUG_ON_PAGE(!PageLocked(page)) ------------[ cut here ]------------ kernel BUG at mm/filemap.c:964! invalid opcode: 0000 [#1] SMP CPU: 1 PID: 22582 Comm: qemu-system-x86 Not tainted 4.11.11-300.fc26.x86_64 #1 task: ffff973131ab2600 task.stack: ffffacc0cba78000 RIP: 0010:unlock_page+0x4a/0x50 RSP: 0018:ffffacc0cba7bca0 EFLAGS: 00010246 RAX: 0000000000000036 RBX: fffff99d09f38000 RCX: 0000000000000006 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff97326148e0c0 RBP: ffffacc0cba7bca0 R08: 00000000000006be R09: 0000000000000004 R10: 00000000000007ae R11: ffffffffb622cbed R12: 0000000000000008 R13: ffff972f9a265240 R14: ffff972de2919740 R15: ffffffffb62da820 FS: 00007f122efff700(0000) GS:ffff973261480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fd52f788ea8 CR3: 000000036d022000 CR4: 00000000003426e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: hugetlb_mcopy_atomic_pte+0xc0/0x320 mcopy_atomic+0x96f/0xbe0 userfaultfd_ioctl+0x218/0xe90 ? __schedule+0x23c/0x8d0 ? hrtimer_start_range_ns+0x1bd/0x330 do_vfs_ioctl+0xa5/0x600 ? do_vfs_ioctl+0xa5/0x600 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x1a/0xa9 Link: http://lkml.kernel.org/r/20170802165145.22628-2-aarcange@xxxxxxxxxx Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Tested-by: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Alexey Perevalov <a.perevalov@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/hugetlb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/hugetlb.c~userfaultfd-hugetlbfs-remove-superfluous-page-unlock-in-vm_shared-case mm/hugetlb.c --- a/mm/hugetlb.c~userfaultfd-hugetlbfs-remove-superfluous-page-unlock-in-vm_shared-case +++ a/mm/hugetlb.c @@ -4062,9 +4062,9 @@ out: return ret; out_release_unlock: spin_unlock(ptl); -out_release_nounlock: if (vm_shared) unlock_page(page); +out_release_nounlock: put_page(page); goto out; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
