* [PATCH] xfs: fix use after free in buf log item unlock assert
@ 2019-02-06 16:01 Brian Foster
2019-02-06 16:10 ` Darrick J. Wong
2019-03-29 14:03 ` Brian Foster
0 siblings, 2 replies; 4+ messages in thread
From: Brian Foster @ 2019-02-06 16:01 UTC (permalink / raw)
To: linux-xfs
The xfs_buf_log_item ->iop_unlock() callback asserts that the buffer
is unlocked when either non-stale or aborted. This assert occurs
after the bli refcount has been dropped and the log item potentially
freed. The aborted check is thus a potential use after free. This
problem has been reproduced with KASAN enabled via generic/475.
Fix up xfs_buf_item_unlock() to query aborted state before the bli
reference is dropped to prevent a potential use after free.
Signed-off-by: Brian Foster <bfoster@redhat.com>
---
fs/xfs/xfs_buf_item.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 010db5f8fb00..65b32acfa0f6 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -605,6 +605,8 @@ xfs_buf_item_unlock(
#if defined(DEBUG) || defined(XFS_WARN)
bool ordered = bip->bli_flags & XFS_BLI_ORDERED;
bool dirty = bip->bli_flags & XFS_BLI_DIRTY;
+ bool aborted = test_bit(XFS_LI_ABORTED,
+ &lip->li_flags);
#endif
trace_xfs_buf_item_unlock(bip);
@@ -633,7 +635,7 @@ xfs_buf_item_unlock(
released = xfs_buf_item_put(bip);
if (hold || (stale && !released))
return;
- ASSERT(!stale || test_bit(XFS_LI_ABORTED, &lip->li_flags));
+ ASSERT(!stale || aborted);
xfs_buf_relse(bp);
}
--
2.17.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] xfs: fix use after free in buf log item unlock assert
2019-02-06 16:01 [PATCH] xfs: fix use after free in buf log item unlock assert Brian Foster
@ 2019-02-06 16:10 ` Darrick J. Wong
2019-03-29 14:03 ` Brian Foster
1 sibling, 0 replies; 4+ messages in thread
From: Darrick J. Wong @ 2019-02-06 16:10 UTC (permalink / raw)
To: Brian Foster; +Cc: linux-xfs
On Wed, Feb 06, 2019 at 11:01:07AM -0500, Brian Foster wrote:
> The xfs_buf_log_item ->iop_unlock() callback asserts that the buffer
> is unlocked when either non-stale or aborted. This assert occurs
> after the bli refcount has been dropped and the log item potentially
> freed. The aborted check is thus a potential use after free. This
> problem has been reproduced with KASAN enabled via generic/475.
>
> Fix up xfs_buf_item_unlock() to query aborted state before the bli
> reference is dropped to prevent a potential use after free.
>
> Signed-off-by: Brian Foster <bfoster@redhat.com>
Seems reasonable,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
--D
> ---
> fs/xfs/xfs_buf_item.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 010db5f8fb00..65b32acfa0f6 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -605,6 +605,8 @@ xfs_buf_item_unlock(
> #if defined(DEBUG) || defined(XFS_WARN)
> bool ordered = bip->bli_flags & XFS_BLI_ORDERED;
> bool dirty = bip->bli_flags & XFS_BLI_DIRTY;
> + bool aborted = test_bit(XFS_LI_ABORTED,
> + &lip->li_flags);
> #endif
>
> trace_xfs_buf_item_unlock(bip);
> @@ -633,7 +635,7 @@ xfs_buf_item_unlock(
> released = xfs_buf_item_put(bip);
> if (hold || (stale && !released))
> return;
> - ASSERT(!stale || test_bit(XFS_LI_ABORTED, &lip->li_flags));
> + ASSERT(!stale || aborted);
> xfs_buf_relse(bp);
> }
>
> --
> 2.17.2
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xfs: fix use after free in buf log item unlock assert
2019-02-06 16:01 [PATCH] xfs: fix use after free in buf log item unlock assert Brian Foster
2019-02-06 16:10 ` Darrick J. Wong
@ 2019-03-29 14:03 ` Brian Foster
2019-03-29 14:13 ` Darrick J. Wong
1 sibling, 1 reply; 4+ messages in thread
From: Brian Foster @ 2019-03-29 14:03 UTC (permalink / raw)
To: linux-xfs
On Wed, Feb 06, 2019 at 11:01:07AM -0500, Brian Foster wrote:
> The xfs_buf_log_item ->iop_unlock() callback asserts that the buffer
> is unlocked when either non-stale or aborted. This assert occurs
> after the bli refcount has been dropped and the log item potentially
> freed. The aborted check is thus a potential use after free. This
> problem has been reproduced with KASAN enabled via generic/475.
>
> Fix up xfs_buf_item_unlock() to query aborted state before the bli
> reference is dropped to prevent a potential use after free.
>
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
Ping on this one.. looks like it was reviewed and maybe fell through the
cracks?
Brian
> fs/xfs/xfs_buf_item.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 010db5f8fb00..65b32acfa0f6 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -605,6 +605,8 @@ xfs_buf_item_unlock(
> #if defined(DEBUG) || defined(XFS_WARN)
> bool ordered = bip->bli_flags & XFS_BLI_ORDERED;
> bool dirty = bip->bli_flags & XFS_BLI_DIRTY;
> + bool aborted = test_bit(XFS_LI_ABORTED,
> + &lip->li_flags);
> #endif
>
> trace_xfs_buf_item_unlock(bip);
> @@ -633,7 +635,7 @@ xfs_buf_item_unlock(
> released = xfs_buf_item_put(bip);
> if (hold || (stale && !released))
> return;
> - ASSERT(!stale || test_bit(XFS_LI_ABORTED, &lip->li_flags));
> + ASSERT(!stale || aborted);
> xfs_buf_relse(bp);
> }
>
> --
> 2.17.2
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xfs: fix use after free in buf log item unlock assert
2019-03-29 14:03 ` Brian Foster
@ 2019-03-29 14:13 ` Darrick J. Wong
0 siblings, 0 replies; 4+ messages in thread
From: Darrick J. Wong @ 2019-03-29 14:13 UTC (permalink / raw)
To: Brian Foster; +Cc: linux-xfs
On Fri, Mar 29, 2019 at 10:03:28AM -0400, Brian Foster wrote:
> On Wed, Feb 06, 2019 at 11:01:07AM -0500, Brian Foster wrote:
> > The xfs_buf_log_item ->iop_unlock() callback asserts that the buffer
> > is unlocked when either non-stale or aborted. This assert occurs
> > after the bli refcount has been dropped and the log item potentially
> > freed. The aborted check is thus a potential use after free. This
> > problem has been reproduced with KASAN enabled via generic/475.
> >
> > Fix up xfs_buf_item_unlock() to query aborted state before the bli
> > reference is dropped to prevent a potential use after free.
> >
> > Signed-off-by: Brian Foster <bfoster@redhat.com>
> > ---
>
> Ping on this one.. looks like it was reviewed and maybe fell through the
> cracks?
Yep. Spreadsheet says it's in 5.0-rc6, and ... totally not upstream. :(
Sorry about that.
--D
> Brian
>
> > fs/xfs/xfs_buf_item.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> > index 010db5f8fb00..65b32acfa0f6 100644
> > --- a/fs/xfs/xfs_buf_item.c
> > +++ b/fs/xfs/xfs_buf_item.c
> > @@ -605,6 +605,8 @@ xfs_buf_item_unlock(
> > #if defined(DEBUG) || defined(XFS_WARN)
> > bool ordered = bip->bli_flags & XFS_BLI_ORDERED;
> > bool dirty = bip->bli_flags & XFS_BLI_DIRTY;
> > + bool aborted = test_bit(XFS_LI_ABORTED,
> > + &lip->li_flags);
> > #endif
> >
> > trace_xfs_buf_item_unlock(bip);
> > @@ -633,7 +635,7 @@ xfs_buf_item_unlock(
> > released = xfs_buf_item_put(bip);
> > if (hold || (stale && !released))
> > return;
> > - ASSERT(!stale || test_bit(XFS_LI_ABORTED, &lip->li_flags));
> > + ASSERT(!stale || aborted);
> > xfs_buf_relse(bp);
> > }
> >
> > --
> > 2.17.2
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-02-06 16:01 [PATCH] xfs: fix use after free in buf log item unlock assert Brian Foster
2019-02-06 16:10 ` Darrick J. Wong
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2019-03-29 14:13 ` Darrick J. Wong
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