Re: [PATCH] mm/hugetlb: Don't call region_abort if region_chg fails

From: Hillf Danton
Date: Fri Mar 24 2017 - 02:03:46 EST


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