On Wed, Jul 09, 2014 at 05:36:24PM -0400, Naoya Horiguchi wrote: > On Wed, Jul 09, 2014 at 04:34:36PM +0300, Kirill A. Shutemov wrote: > > On Tue, Jul 01, 2014 at 01:07:31PM -0400, Naoya Horiguchi wrote: > > > This patch makes do_mincore() use walk_page_vma(), which reduces many lines > > > of code by using common page table walk code. > > > > > > ChangeLog v4: > > > - remove redundant vma > > > > > > ChangeLog v3: > > > - add NULL vma check in mincore_unmapped_range() > > > - don't use pte_entry() > > > > > > ChangeLog v2: > > > - change type of args of callbacks to void * > > > - move definition of mincore_walk to the start of the function to fix compiler > > > warning > > > > > > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > > > > Trinity crases this implementation of mincore pretty easily: > > > > [ 42.775369] BUG: unable to handle kernel paging request at ffff88007bb61000 > > [ 42.776656] IP: [<ffffffff81126f8f>] mincore_unmapped_range+0xdf/0x100 > > Thanks for your testing/reporting. > > ... > > > > Looks like 'vec' overflow. I don't see what could prevent do_mincore() to > > write more than PAGE_SIZE to 'vec'. > > I found the miscalculation of walk->private (vec) on thp and hugetlbfs. > I confirmed that the reported problem is fixed (I checked that trinity > never triggers the reported BUG) with the following changes on this patch. With the changes: [ 26.850945] BUG: unable to handle kernel paging request at ffff880852d8c000 [ 26.852718] IP: [<ffffffff81126de7>] mincore_hugetlb+0x27/0x50 [ 26.853527] PGD 2ef6067 PUD 2ef9067 PMD 87fd4a067 PTE 8000000852d8c060 [ 26.854462] Oops: 0002 [#1] SMP DEBUG_PAGEALLOC [ 26.854752] Modules linked in: [ 26.854752] CPU: 5 PID: 170 Comm: trinity-c5 Not tainted 3.16.0-rc4-next-20140709-00013-g28e4629f71a8-dirty #1453 [ 26.854752] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 26.854752] task: ffff880852d22890 ti: ffff880852d24000 task.ti: ffff880852d24000 [ 26.854752] RIP: 0010:[<ffffffff81126de7>] [<ffffffff81126de7>] mincore_hugetlb+0x27/0x50 [ 26.854752] RSP: 0018:ffff880852d27e28 EFLAGS: 00010206 [ 26.854752] RAX: ffff880852d8c000 RBX: 00007f9fb2200000 RCX: 00007f9fb2200000 [ 26.854752] RDX: 00007f9fb2001000 RSI: ffffffffffe00000 RDI: ffff88084f3edc80 [ 26.854752] RBP: ffff880852d27e28 R08: ffff880852d27f10 R09: ffffffff81126dc0 [ 26.854752] R10: 0000000000000000 R11: 0000000000000001 R12: 00007f9fde000000 [ 26.854752] R13: ffffffff82e32580 R14: 00007f9fb2000000 R15: ffff880852d27f10 [ 26.854752] FS: 00007f9fe1bde700(0000) GS:ffff88085a000000(0000) knlGS:0000000000000000 [ 26.854752] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 26.854752] CR2: ffff880852d8c000 CR3: 0000000852d12000 CR4: 00000000000006e0 [ 26.854752] Stack: [ 26.854752] ffff880852d27eb8 ffffffff81135e24 ffff880852ce01d8 0000000000000282 [ 26.854752] ffff880852ce01d8 ffff880852d22890 00007f9fde000000 ffff880852d27eb0 [ 26.854752] 0000000000000282 0000000000000000 ffffffff81127399 0000000000000282 [ 26.854752] Call Trace: [ 26.854752] [<ffffffff81135e24>] __walk_page_range+0x3f4/0x450 [ 26.854752] [<ffffffff81127399>] ? SyS_mincore+0x179/0x270 [ 26.854752] [<ffffffff81136031>] walk_page_vma+0x71/0x90 [ 26.854752] [<ffffffff811273fe>] SyS_mincore+0x1de/0x270 [ 26.854752] [<ffffffff81126fb0>] ? mincore_unmapped_range+0x100/0x100 [ 26.854752] [<ffffffff81126eb0>] ? mincore_page+0xa0/0xa0 [ 26.854752] [<ffffffff81126dc0>] ? handle_mm_fault+0xd30/0xd30 [ 26.854752] [<ffffffff81746b12>] system_call_fastpath+0x16/0x1b [ 26.854752] Code: 0f 1f 40 00 55 48 85 ff 49 8b 40 38 48 89 e5 74 33 48 83 3f 00 40 0f 95 c6 48 39 ca 74 19 66 0f 1f 44 00 00 48 81 c2 00 10 00 00 <40> 88 30 48 83 c0 01 48 39 d1 75 ed 49 89 40 38 31 c0 5d c3 0f [ 26.854752] RIP [<ffffffff81126de7>] mincore_hugetlb+0x27/0x50 [ 26.854752] RSP <ffff880852d27e28> [ 26.854752] CR2: ffff880852d8c000 [ 26.854752] ---[ end trace 536bbdef8c6d5b03 ]--- Could you explain to me how you protect 'vec' from being overflowed? I don't any code for that. -- 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>