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

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

[Mike Kravetz]

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@google.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 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

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

[Hillf Danton]

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@google.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> ---

Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>

>  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

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

[Hillf Danton]

Reply again with Andrew's mail address corrected:)

-'Andrew Morton' <akpm@linux^Coundation.org>
+'Andrew Morton' <akpm@linux-foundation.org>
> 
> 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@google.com>
> > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> > ---
> 
> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> 
> >  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

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