From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Elena Reshetova <elena.reshetova@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
peterz@infradead.org, gregkh@linuxfoundation.org,
david@fromorbit.com, Hans Liljestrand <ishkamiel@gmail.com>,
Kees Cook <keescook@chromium.org>,
David Windsor <dwindsor@gmail.com>
Subject: Re: [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to refcount_t
Date: Mon, 6 Mar 2017 11:14:46 -0800 [thread overview]
Message-ID: <20170306191446.GE5280@birch.djwong.org> (raw)
In-Reply-To: <1488358060-693-5-git-send-email-elena.reshetova@intel.com>
On Wed, Mar 01, 2017 at 10:47:39AM +0200, Elena Reshetova wrote:
> refcount_t type and corresponding API should be
> used instead of atomic_t when the variable is used as
> a reference counter. This allows to avoid accidental
> refcounter overflows that might lead to use-after-free
> situations.
>
> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
> Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: David Windsor <dwindsor@gmail.com>
> ---
> fs/xfs/xfs_refcount_item.c | 4 ++--
> fs/xfs/xfs_refcount_item.h | 4 +++-
> 2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/xfs_refcount_item.c b/fs/xfs/xfs_refcount_item.c
> index 6e4c744..61bc570 100644
> --- a/fs/xfs/xfs_refcount_item.c
> +++ b/fs/xfs/xfs_refcount_item.c
> @@ -205,7 +205,7 @@ xfs_cui_init(
> cuip->cui_format.cui_nextents = nextents;
> cuip->cui_format.cui_id = (uintptr_t)(void *)cuip;
> atomic_set(&cuip->cui_next_extent, 0);
> - atomic_set(&cuip->cui_refcount, 2);
> + refcount_set(&cuip->cui_refcount, 2);
I'm assuming the refcount design is ok with the log item refcounts
starting at 2 and marching down to zero? The code seems to be
fine with it; I just want to make sure everyone's ok with supporting
this use case.
> return cuip;
> }
> @@ -221,7 +221,7 @@ void
> xfs_cui_release(
> struct xfs_cui_log_item *cuip)
> {
> - if (atomic_dec_and_test(&cuip->cui_refcount)) {
> + if (refcount_dec_and_test(&cuip->cui_refcount)) {
I suppose it's useful to have refcount_dec_and_test complain loudly if
we ever have a dangling pointer... Friday I was chasing a possible
use-after-free of the EFI items in generic/388.
> xfs_trans_ail_remove(&cuip->cui_item, SHUTDOWN_LOG_IO_ERROR);
> xfs_cui_item_free(cuip);
> }
> diff --git a/fs/xfs/xfs_refcount_item.h b/fs/xfs/xfs_refcount_item.h
> index 5b74ddd..7f23ff8 100644
> --- a/fs/xfs/xfs_refcount_item.h
> +++ b/fs/xfs/xfs_refcount_item.h
> @@ -20,6 +20,8 @@
> #ifndef __XFS_REFCOUNT_ITEM_H__
> #define __XFS_REFCOUNT_ITEM_H__
>
> +#include <linux/refcount.h>
I still think this include should go in xfs_linux.h, the same as most of
the other linux/*.h includes in XFS.
--D
> +
> /*
> * There are (currently) two pairs of refcount btree redo item types:
> * increase and decrease. The log items for these are CUI (refcount
> @@ -63,7 +65,7 @@ struct kmem_zone;
> */
> struct xfs_cui_log_item {
> struct xfs_log_item cui_item;
> - atomic_t cui_refcount;
> + refcount_t cui_refcount;
> atomic_t cui_next_extent;
> unsigned long cui_flags; /* misc flags */
> struct xfs_cui_log_format cui_format;
> --
> 2.7.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2017-03-07 0:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-01 8:47 [PATCH 0/5] fs, xfs atomic_t to refcount_t conversions version 2 Elena Reshetova
2017-03-01 8:47 ` [PATCH 1/5] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t Elena Reshetova
2017-03-01 8:47 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount " Elena Reshetova
2017-03-01 8:47 ` [PATCH 3/5] fs, xfs: convert xlog_ticket.t_ref " Elena Reshetova
2017-03-01 8:47 ` [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount " Elena Reshetova
2017-03-06 19:14 ` Darrick J. Wong [this message]
2017-03-07 17:33 ` Reshetova, Elena
2017-03-07 20:30 ` Darrick J. Wong
2017-03-01 8:47 ` [PATCH 5/5] fs, xfs: convert xfs_rui_log_item.rui_refcount " Elena Reshetova
2017-03-08 8:53 [PATCH 0/5] fs, xfs refcount conversions Elena Reshetova
2017-03-08 8:53 ` [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to refcount_t Elena Reshetova
2017-10-20 11:07 [PATCH 0/5] xfs refcount conversions Elena Reshetova
2017-10-20 11:07 ` [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to refcount_t Elena Reshetova
2017-11-29 11:37 [PATCH 0/5] v2 xfs refcount conversions Elena Reshetova
2017-11-29 11:38 ` [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to refcount_t Elena Reshetova
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