On 12/01/2015 06:04 AM, Dmitry Vyukov wrote: > Hello, > > The following program leaks memory: > > // autogenerated by syzkaller (http://github.com/google/syzkaller) > #include <syscall.h> > #include <string.h> > #include <stdint.h> > > #define SYS_mlock2 325 > > int main() > { > syscall(SYS_mmap, 0x20000000ul, 0x1000ul, 0x3ul, 0x45031ul, > 0xfffffffffffffffful, 0x0ul); > syscall(SYS_mlock2, 0x20000000ul, 0x1000ul, 0x1ul, 0, 0, 0); > return 0; > } > > unreferenced object 0xffff88002eaafd88 (size 32): > comm "a.out", pid 5063, jiffies 4295774645 (age 15.810s) > hex dump (first 32 bytes): > 28 e9 4e 63 00 88 ff ff 28 e9 4e 63 00 88 ff ff (.Nc....(.Nc.... > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > [< inline >] kmalloc include/linux/slab.h:458 > [<ffffffff815efa64>] region_chg+0x2d4/0x6b0 mm/hugetlb.c:398 > [<ffffffff815f0c63>] __vma_reservation_common+0x2c3/0x390 mm/hugetlb.c:1791 > [< inline >] vma_needs_reservation mm/hugetlb.c:1813 > [<ffffffff815f658e>] alloc_huge_page+0x19e/0xc70 mm/hugetlb.c:1845 > [< inline >] hugetlb_no_page mm/hugetlb.c:3543 > [<ffffffff815fc561>] hugetlb_fault+0x7a1/0x1250 mm/hugetlb.c:3717 > [<ffffffff815fd349>] follow_hugetlb_page+0x339/0xc70 mm/hugetlb.c:3880 > [<ffffffff815a2bb2>] __get_user_pages+0x542/0xf30 mm/gup.c:497 > [<ffffffff815a400e>] populate_vma_page_range+0xde/0x110 mm/gup.c:919 > [<ffffffff815a4207>] __mm_populate+0x1c7/0x310 mm/gup.c:969 > [<ffffffff815b74f1>] do_mlock+0x291/0x360 mm/mlock.c:637 > [< inline >] SYSC_mlock2 mm/mlock.c:658 > [<ffffffff815b7a4b>] SyS_mlock2+0x4b/0x70 mm/mlock.c:648 > > If this program run in a loop number of objects in kmalloc-32 slab > indeed grows infinitely. > > On commit 31ade3b83e1821da5fbb2f11b5b3d4ab2ec39db8 (Nov 29). > > There seems to be another leak if nrg is not NULL on this path, but > it's not what happens in my case since the WARNING does not fire. > Still something to fix: > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 827bb02..e97a31b 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -372,8 +372,10 @@ retry_locked: > spin_unlock(&resv->lock); > > trg = kmalloc(sizeof(*trg), GFP_KERNEL); > - if (!trg) > + if (!trg) { > + WARN_ON(nrg != NULL); > return -ENOMEM; > + } > > spin_lock(&resv->lock); > list_add(&trg->link, &resv->region_cache); > > Thanks Dmitry, If nrg is not NULL, then it was added to the resv map and 'should' be free'ed when the map is free'ed. This is not optimal, but I do not think it would lead to a leak. I'll take a close look at this code with an emphasis on the leak you discovered. -- Mike Kravetz > Thanks > -- 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>