On March 24, 2017 12:03 PM Mike Kravetz wrote: > > Changes to hugetlbfs reservation maps is a two step process. The first > step is a call to region_chg to determine what needs to be changed, and > prepare that change. This should be followed by a call to call to > region_add to commit the change, or region_abort to abort the change. > > The error path in hugetlb_reserve_pages called region_abort after a > failed call to region_chg. As a result, the adds_in_progress counter > in the reservation map is off by 1. This is caught by a VM_BUG_ON > in resv_map_release when the reservation map is freed. > > syzkaller fuzzer found this bug, that resulted in the following: > > kernel BUG at mm/hugetlb.c:742! > Call Trace: > hugetlbfs_evict_inode+0x7b/0xa0 fs/hugetlbfs/inode.c:493 > evict+0x481/0x920 fs/inode.c:553 > iput_final fs/inode.c:1515 [inline] > iput+0x62b/0xa20 fs/inode.c:1542 > hugetlb_file_setup+0x593/0x9f0 fs/hugetlbfs/inode.c:1306 > newseg+0x422/0xd30 ipc/shm.c:575 > ipcget_new ipc/util.c:285 [inline] > ipcget+0x21e/0x580 ipc/util.c:639 > SYSC_shmget ipc/shm.c:673 [inline] > SyS_shmget+0x158/0x230 ipc/shm.c:657 > entry_SYSCALL_64_fastpath+0x1f/0xc2 > RIP: resv_map_release+0x265/0x330 mm/hugetlb.c:742 > > Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > --- Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> > mm/hugetlb.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index c7025c1..c65d45c 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -4233,7 +4233,9 @@ int hugetlb_reserve_pages(struct inode *inode, > return 0; > out_err: > if (!vma || vma->vm_flags & VM_MAYSHARE) > - region_abort(resv_map, from, to); > + /* Don't call region_abort if region_chg failed */ > + if (chg >= 0) > + region_abort(resv_map, from, to); > if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) > kref_put(&resv_map->refs, resv_map_release); > return ret; > -- > 2.7.4 -- 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>
