* [PATCH 0/5] v2 xfs refcount conversions
@ 2017-11-29 11:37 Elena Reshetova
2017-11-29 11:37 ` [PATCH 1/5] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t Elena Reshetova
` (4 more replies)
0 siblings, 5 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-11-29 11:37 UTC (permalink / raw)
To: david
Cc: darrick.wong, linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
Hi Dave,
Following our previous conversation I have updated each
patch with a highlight of potential problematic places
with regards to the memory ordering guarantees, as well
as link to the document I am working on to clarify the
matter.
While I didn't see any issues with these 5 particular
conversions, of course I don't understand code anywhere
good enough to make the final claim that "everything is
100% ok".
Please let me know what kind of other clarification or
anything is needed that can help you to make the needed
verification.
Best Regards,
Elena.
Changes in v2:
- each patch now has a clarification on potential
problematic places with regards to the memory ordering
guarantees as well as reference to a hopefully soon to be
merged more extensive documentation on the
differences between atomic_t and refcount_t on ordering.
- Rebase on linux-next master.
This series, for xfs, replaces atomic_t reference
counters with the new refcount_t type and API (see include/linux/refcount.h).
By doing this we prevent intentional or accidental
underflows or overflows that can lead to use-after-free vulnerabilities.
The patches are fully independent and can be cherry-picked separately.
If there are no objections to the patches, please merge them via respective trees.
Elena Reshetova (5):
fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to
refcount_t
fs, xfs: convert xlog_ticket.t_ref from atomic_t to refcount_t
fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_rui_log_item.rui_refcount from atomic_t to
refcount_t
fs/xfs/xfs_bmap_item.c | 6 +++---
fs/xfs/xfs_bmap_item.h | 2 +-
fs/xfs/xfs_extfree_item.c | 6 +++---
fs/xfs/xfs_extfree_item.h | 2 +-
fs/xfs/xfs_linux.h | 1 +
fs/xfs/xfs_log.c | 10 +++++-----
fs/xfs/xfs_log_priv.h | 2 +-
fs/xfs/xfs_refcount_item.c | 6 +++---
fs/xfs/xfs_refcount_item.h | 2 +-
fs/xfs/xfs_rmap_item.c | 6 +++---
fs/xfs/xfs_rmap_item.h | 2 +-
11 files changed, 23 insertions(+), 22 deletions(-)
--
2.7.4
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 1/5] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t
2017-11-29 11:37 [PATCH 0/5] v2 xfs refcount conversions Elena Reshetova
@ 2017-11-29 11:37 ` Elena Reshetova
2017-11-29 11:38 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount " Elena Reshetova
` (3 subsequent siblings)
4 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-11-29 11:37 UTC (permalink / raw)
To: david
Cc: darrick.wong, linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable xfs_bui_log_item.bui_refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
**Important note for maintainers:
Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.
The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.
Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.
For the xfs_bui_log_item.bui_refcount it might make a difference
in following places:
- xfs_bui_release(): decrement in refcount_dec_and_test() only
provides RELEASE ordering and control dependency on success
vs. fully ordered atomic counterpart
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
fs/xfs/xfs_bmap_item.c | 6 +++---
fs/xfs/xfs_bmap_item.h | 2 +-
fs/xfs/xfs_linux.h | 1 +
3 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
index dd136f7..0f2e3d8 100644
--- a/fs/xfs/xfs_bmap_item.c
+++ b/fs/xfs/xfs_bmap_item.c
@@ -201,7 +201,7 @@ xfs_bui_init(
buip->bui_format.bui_nextents = XFS_BUI_MAX_FAST_EXTENTS;
buip->bui_format.bui_id = (uintptr_t)(void *)buip;
atomic_set(&buip->bui_next_extent, 0);
- atomic_set(&buip->bui_refcount, 2);
+ refcount_set(&buip->bui_refcount, 2);
return buip;
}
@@ -217,8 +217,8 @@ void
xfs_bui_release(
struct xfs_bui_log_item *buip)
{
- ASSERT(atomic_read(&buip->bui_refcount) > 0);
- if (atomic_dec_and_test(&buip->bui_refcount)) {
+ ASSERT(refcount_read(&buip->bui_refcount) > 0);
+ if (refcount_dec_and_test(&buip->bui_refcount)) {
xfs_trans_ail_remove(&buip->bui_item, SHUTDOWN_LOG_IO_ERROR);
xfs_bui_item_free(buip);
}
diff --git a/fs/xfs/xfs_bmap_item.h b/fs/xfs/xfs_bmap_item.h
index c867daa..7048b14 100644
--- a/fs/xfs/xfs_bmap_item.h
+++ b/fs/xfs/xfs_bmap_item.h
@@ -61,7 +61,7 @@ struct kmem_zone;
*/
struct xfs_bui_log_item {
struct xfs_log_item bui_item;
- atomic_t bui_refcount;
+ refcount_t bui_refcount;
atomic_t bui_next_extent;
unsigned long bui_flags; /* misc flags */
struct xfs_bui_log_format bui_format;
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 99562ec..31658ac 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -20,6 +20,7 @@
#include <linux/types.h>
#include <linux/uuid.h>
+#include <linux/refcount.h>
/*
* Kernel specific type declarations for XFS
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t
2017-11-29 11:37 [PATCH 0/5] v2 xfs refcount conversions Elena Reshetova
2017-11-29 11:37 ` [PATCH 1/5] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t Elena Reshetova
@ 2017-11-29 11:38 ` Elena Reshetova
2017-11-29 11:38 ` [PATCH 3/5] fs, xfs: convert xlog_ticket.t_ref " Elena Reshetova
` (2 subsequent siblings)
4 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-11-29 11:38 UTC (permalink / raw)
To: david
Cc: darrick.wong, linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable xfs_efi_log_item.efi_refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
**Important note for maintainers:
Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.
The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.
Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.
For the xfs_efi_log_item.efi_refcount it might make a difference
in following places:
- xfs_efi_release(): decrement in refcount_dec_and_test() only
provides RELEASE ordering and control dependency on success
vs. fully ordered atomic counterpart
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
fs/xfs/xfs_extfree_item.c | 6 +++---
fs/xfs/xfs_extfree_item.h | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
index 44f8c54..dfe2bcb 100644
--- a/fs/xfs/xfs_extfree_item.c
+++ b/fs/xfs/xfs_extfree_item.c
@@ -220,7 +220,7 @@ xfs_efi_init(
efip->efi_format.efi_nextents = nextents;
efip->efi_format.efi_id = (uintptr_t)(void *)efip;
atomic_set(&efip->efi_next_extent, 0);
- atomic_set(&efip->efi_refcount, 2);
+ refcount_set(&efip->efi_refcount, 2);
return efip;
}
@@ -290,8 +290,8 @@ void
xfs_efi_release(
struct xfs_efi_log_item *efip)
{
- ASSERT(atomic_read(&efip->efi_refcount) > 0);
- if (atomic_dec_and_test(&efip->efi_refcount)) {
+ ASSERT(refcount_read(&efip->efi_refcount) > 0);
+ if (refcount_dec_and_test(&efip->efi_refcount)) {
xfs_trans_ail_remove(&efip->efi_item, SHUTDOWN_LOG_IO_ERROR);
xfs_efi_item_free(efip);
}
diff --git a/fs/xfs/xfs_extfree_item.h b/fs/xfs/xfs_extfree_item.h
index a32c794..fadf736 100644
--- a/fs/xfs/xfs_extfree_item.h
+++ b/fs/xfs/xfs_extfree_item.h
@@ -64,7 +64,7 @@ struct kmem_zone;
*/
typedef struct xfs_efi_log_item {
xfs_log_item_t efi_item;
- atomic_t efi_refcount;
+ refcount_t efi_refcount;
atomic_t efi_next_extent;
unsigned long efi_flags; /* misc flags */
xfs_efi_log_format_t efi_format;
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 3/5] fs, xfs: convert xlog_ticket.t_ref from atomic_t to refcount_t
2017-11-29 11:37 [PATCH 0/5] v2 xfs refcount conversions Elena Reshetova
2017-11-29 11:37 ` [PATCH 1/5] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t Elena Reshetova
2017-11-29 11:38 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount " Elena Reshetova
@ 2017-11-29 11:38 ` Elena Reshetova
2017-11-29 11:38 ` [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount " Elena Reshetova
2017-11-29 11:38 ` [PATCH 5/5] fs, xfs: convert xfs_rui_log_item.rui_refcount " Elena Reshetova
4 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-11-29 11:38 UTC (permalink / raw)
To: david
Cc: darrick.wong, linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable xlog_ticket.t_ref is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
**Important note for maintainers:
Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.
The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.
Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.
For the xlog_ticket.t_ref it might make a difference
in following places:
- xfs_log_ticket_put(): decrement in refcount_dec_and_test() only
provides RELEASE ordering and control dependency on success
vs. fully ordered atomic counterpart
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
fs/xfs/xfs_log.c | 10 +++++-----
fs/xfs/xfs_log_priv.h | 2 +-
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index a503af9..6e1528f 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -3600,8 +3600,8 @@ void
xfs_log_ticket_put(
xlog_ticket_t *ticket)
{
- ASSERT(atomic_read(&ticket->t_ref) > 0);
- if (atomic_dec_and_test(&ticket->t_ref))
+ ASSERT(refcount_read(&ticket->t_ref) > 0);
+ if (refcount_dec_and_test(&ticket->t_ref))
kmem_zone_free(xfs_log_ticket_zone, ticket);
}
@@ -3609,8 +3609,8 @@ xlog_ticket_t *
xfs_log_ticket_get(
xlog_ticket_t *ticket)
{
- ASSERT(atomic_read(&ticket->t_ref) > 0);
- atomic_inc(&ticket->t_ref);
+ ASSERT(refcount_read(&ticket->t_ref) > 0);
+ refcount_inc(&ticket->t_ref);
return ticket;
}
@@ -3732,7 +3732,7 @@ xlog_ticket_alloc(
unit_res = xfs_log_calc_unit_res(log->l_mp, unit_bytes);
- atomic_set(&tic->t_ref, 1);
+ refcount_set(&tic->t_ref, 1);
tic->t_task = current;
INIT_LIST_HEAD(&tic->t_queue);
tic->t_unit_res = unit_res;
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 1299759..7482145 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -168,7 +168,7 @@ typedef struct xlog_ticket {
struct list_head t_queue; /* reserve/write queue */
struct task_struct *t_task; /* task that owns this ticket */
xlog_tid_t t_tid; /* transaction identifier : 4 */
- atomic_t t_ref; /* ticket reference count : 4 */
+ refcount_t t_ref; /* ticket reference count : 4 */
int t_curr_res; /* current reservation in bytes : 4 */
int t_unit_res; /* unit reservation in bytes : 4 */
char t_ocnt; /* original count : 1 */
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to refcount_t
2017-11-29 11:37 [PATCH 0/5] v2 xfs refcount conversions Elena Reshetova
` (2 preceding siblings ...)
2017-11-29 11:38 ` [PATCH 3/5] fs, xfs: convert xlog_ticket.t_ref " Elena Reshetova
@ 2017-11-29 11:38 ` Elena Reshetova
2017-11-29 11:38 ` [PATCH 5/5] fs, xfs: convert xfs_rui_log_item.rui_refcount " Elena Reshetova
4 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-11-29 11:38 UTC (permalink / raw)
To: david
Cc: darrick.wong, linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable xfs_cui_log_item.cui_refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
**Important note for maintainers:
Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.
The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.
Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.
For the xfs_cui_log_item.cui_refcount it might make a difference
in following places:
- xfs_cui_release(): decrement in refcount_dec_and_test() only
provides RELEASE ordering and control dependency on success
vs. fully ordered atomic counterpart
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
fs/xfs/xfs_refcount_item.c | 6 +++---
fs/xfs/xfs_refcount_item.h | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_refcount_item.c b/fs/xfs/xfs_refcount_item.c
index 8f2e2fa..004d002 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);
return cuip;
}
@@ -221,8 +221,8 @@ void
xfs_cui_release(
struct xfs_cui_log_item *cuip)
{
- ASSERT(atomic_read(&cuip->cui_refcount) > 0);
- if (atomic_dec_and_test(&cuip->cui_refcount)) {
+ ASSERT(refcount_read(&cuip->cui_refcount) > 0);
+ if (refcount_dec_and_test(&cuip->cui_refcount)) {
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..abc0377 100644
--- a/fs/xfs/xfs_refcount_item.h
+++ b/fs/xfs/xfs_refcount_item.h
@@ -63,7 +63,7 @@ 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
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 5/5] fs, xfs: convert xfs_rui_log_item.rui_refcount from atomic_t to refcount_t
2017-11-29 11:37 [PATCH 0/5] v2 xfs refcount conversions Elena Reshetova
` (3 preceding siblings ...)
2017-11-29 11:38 ` [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount " Elena Reshetova
@ 2017-11-29 11:38 ` Elena Reshetova
4 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-11-29 11:38 UTC (permalink / raw)
To: david
Cc: darrick.wong, linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable xfs_rui_log_item.rui_refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
**Important note for maintainers:
Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.
The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.
Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.
For the xfs_rui_log_item.rui_refcount it might make a difference
in following places:
- xfs_rui_release(): decrement in refcount_dec_and_test() only
provides RELEASE ordering and control dependency on success
vs. fully ordered atomic counterpart
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
fs/xfs/xfs_rmap_item.c | 6 +++---
fs/xfs/xfs_rmap_item.h | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_rmap_item.c b/fs/xfs/xfs_rmap_item.c
index f3b139c..f914829f 100644
--- a/fs/xfs/xfs_rmap_item.c
+++ b/fs/xfs/xfs_rmap_item.c
@@ -204,7 +204,7 @@ xfs_rui_init(
ruip->rui_format.rui_nextents = nextents;
ruip->rui_format.rui_id = (uintptr_t)(void *)ruip;
atomic_set(&ruip->rui_next_extent, 0);
- atomic_set(&ruip->rui_refcount, 2);
+ refcount_set(&ruip->rui_refcount, 2);
return ruip;
}
@@ -243,8 +243,8 @@ void
xfs_rui_release(
struct xfs_rui_log_item *ruip)
{
- ASSERT(atomic_read(&ruip->rui_refcount) > 0);
- if (atomic_dec_and_test(&ruip->rui_refcount)) {
+ ASSERT(refcount_read(&ruip->rui_refcount) > 0);
+ if (refcount_dec_and_test(&ruip->rui_refcount)) {
xfs_trans_ail_remove(&ruip->rui_item, SHUTDOWN_LOG_IO_ERROR);
xfs_rui_item_free(ruip);
}
diff --git a/fs/xfs/xfs_rmap_item.h b/fs/xfs/xfs_rmap_item.h
index 340c968..1e425a9 100644
--- a/fs/xfs/xfs_rmap_item.h
+++ b/fs/xfs/xfs_rmap_item.h
@@ -64,7 +64,7 @@ struct kmem_zone;
*/
struct xfs_rui_log_item {
struct xfs_log_item rui_item;
- atomic_t rui_refcount;
+ refcount_t rui_refcount;
atomic_t rui_next_extent;
unsigned long rui_flags; /* misc flags */
struct xfs_rui_log_format rui_format;
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 0/5] xfs refcount conversions
@ 2017-10-20 11:07 Elena Reshetova
2017-10-20 11:07 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Elena Reshetova
0 siblings, 1 reply; 9+ messages in thread
From: Elena Reshetova @ 2017-10-20 11:07 UTC (permalink / raw)
To: darrick.wong; +Cc: linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
Note: our previous thread didn't finish in any conclusion, so
I am resending this now (rebased at latest linux-next) to revive
the discussion. refcount_t is slowly becoming a standard for
refcounters and we would really like to make all conversions
done where it is applicable.
******
This series, for xfs, replaces atomic_t reference
counters with the new refcount_t type and API (see include/linux/refcount.h).
By doing this we prevent intentional or accidental
underflows or overflows that can lead to use-after-free vulnerabilities.
The patches are fully independent and can be cherry-picked separately.
If there are no objections to the patches, please merge them via respective trees.
Elena Reshetova (5):
fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to
refcount_t
fs, xfs: convert xlog_ticket.t_ref from atomic_t to refcount_t
fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_rui_log_item.rui_refcount from atomic_t to
refcount_t
fs/xfs/xfs_bmap_item.c | 6 +++---
fs/xfs/xfs_bmap_item.h | 2 +-
fs/xfs/xfs_extfree_item.c | 6 +++---
fs/xfs/xfs_extfree_item.h | 2 +-
fs/xfs/xfs_linux.h | 1 +
fs/xfs/xfs_log.c | 10 +++++-----
fs/xfs/xfs_log_priv.h | 2 +-
fs/xfs/xfs_refcount_item.c | 6 +++---
fs/xfs/xfs_refcount_item.h | 2 +-
fs/xfs/xfs_rmap_item.c | 6 +++---
fs/xfs/xfs_rmap_item.h | 2 +-
11 files changed, 23 insertions(+), 22 deletions(-)
--
2.7.4
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t
2017-10-20 11:07 [PATCH 0/5] xfs refcount conversions Elena Reshetova
@ 2017-10-20 11:07 ` Elena Reshetova
0 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-10-20 11:07 UTC (permalink / raw)
To: darrick.wong; +Cc: linux-kernel, linux-xfs, peterz, keescook, Elena Reshetova
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable xfs_efi_log_item.efi_refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
fs/xfs/xfs_extfree_item.c | 6 +++---
fs/xfs/xfs_extfree_item.h | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
index 44f8c54..dfe2bcb 100644
--- a/fs/xfs/xfs_extfree_item.c
+++ b/fs/xfs/xfs_extfree_item.c
@@ -220,7 +220,7 @@ xfs_efi_init(
efip->efi_format.efi_nextents = nextents;
efip->efi_format.efi_id = (uintptr_t)(void *)efip;
atomic_set(&efip->efi_next_extent, 0);
- atomic_set(&efip->efi_refcount, 2);
+ refcount_set(&efip->efi_refcount, 2);
return efip;
}
@@ -290,8 +290,8 @@ void
xfs_efi_release(
struct xfs_efi_log_item *efip)
{
- ASSERT(atomic_read(&efip->efi_refcount) > 0);
- if (atomic_dec_and_test(&efip->efi_refcount)) {
+ ASSERT(refcount_read(&efip->efi_refcount) > 0);
+ if (refcount_dec_and_test(&efip->efi_refcount)) {
xfs_trans_ail_remove(&efip->efi_item, SHUTDOWN_LOG_IO_ERROR);
xfs_efi_item_free(efip);
}
diff --git a/fs/xfs/xfs_extfree_item.h b/fs/xfs/xfs_extfree_item.h
index a32c794..fadf736 100644
--- a/fs/xfs/xfs_extfree_item.h
+++ b/fs/xfs/xfs_extfree_item.h
@@ -64,7 +64,7 @@ struct kmem_zone;
*/
typedef struct xfs_efi_log_item {
xfs_log_item_t efi_item;
- atomic_t efi_refcount;
+ refcount_t efi_refcount;
atomic_t efi_next_extent;
unsigned long efi_flags; /* misc flags */
xfs_efi_log_format_t efi_format;
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 0/5] fs, xfs refcount conversions
@ 2017-03-08 8:53 Elena Reshetova
2017-03-08 8:53 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Elena Reshetova
0 siblings, 1 reply; 9+ messages in thread
From: Elena Reshetova @ 2017-03-08 8:53 UTC (permalink / raw)
To: darrick.wong; +Cc: linux-kernel, linux-xfs, Elena Reshetova
v3:
* fixed header file inclusion
Now when new refcount_t type and API are finally merged
(see include/linux/refcount.h), the following
patches convert various refcounters in the xfs susystem from atomic_t
to refcount_t. By doing this we prevent intentional or accidental
underflows or overflows that can led to use-after-free vulnerabilities.
Elena Reshetova (5):
fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to
refcount_t
fs, xfs: convert xlog_ticket.t_ref from atomic_t to refcount_t
fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_rui_log_item.rui_refcount from atomic_t to
refcount_t
fs/xfs/xfs_bmap_item.c | 4 ++--
fs/xfs/xfs_bmap_item.h | 2 +-
fs/xfs/xfs_extfree_item.c | 4 ++--
fs/xfs/xfs_extfree_item.h | 2 +-
fs/xfs/xfs_linux.h | 1 +
fs/xfs/xfs_log.c | 10 +++++-----
fs/xfs/xfs_log_priv.h | 2 +-
fs/xfs/xfs_refcount_item.c | 4 ++--
fs/xfs/xfs_refcount_item.h | 2 +-
fs/xfs/xfs_rmap_item.c | 4 ++--
fs/xfs/xfs_rmap_item.h | 2 +-
11 files changed, 19 insertions(+), 18 deletions(-)
--
2.7.4
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t
2017-03-08 8:53 [PATCH 0/5] fs, xfs refcount conversions Elena Reshetova
@ 2017-03-08 8:53 ` Elena Reshetova
0 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-03-08 8:53 UTC (permalink / raw)
To: darrick.wong
Cc: linux-kernel, linux-xfs, Elena Reshetova, Hans Liljestrand,
Kees Cook, David Windsor
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_extfree_item.c | 4 ++--
fs/xfs/xfs_extfree_item.h | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
index d7bc149..4e0acf0 100644
--- a/fs/xfs/xfs_extfree_item.c
+++ b/fs/xfs/xfs_extfree_item.c
@@ -220,7 +220,7 @@ xfs_efi_init(
efip->efi_format.efi_nextents = nextents;
efip->efi_format.efi_id = (uintptr_t)(void *)efip;
atomic_set(&efip->efi_next_extent, 0);
- atomic_set(&efip->efi_refcount, 2);
+ refcount_set(&efip->efi_refcount, 2);
return efip;
}
@@ -290,7 +290,7 @@ void
xfs_efi_release(
struct xfs_efi_log_item *efip)
{
- if (atomic_dec_and_test(&efip->efi_refcount)) {
+ if (refcount_dec_and_test(&efip->efi_refcount)) {
xfs_trans_ail_remove(&efip->efi_item, SHUTDOWN_LOG_IO_ERROR);
xfs_efi_item_free(efip);
}
diff --git a/fs/xfs/xfs_extfree_item.h b/fs/xfs/xfs_extfree_item.h
index a32c794..fadf736 100644
--- a/fs/xfs/xfs_extfree_item.h
+++ b/fs/xfs/xfs_extfree_item.h
@@ -64,7 +64,7 @@ struct kmem_zone;
*/
typedef struct xfs_efi_log_item {
xfs_log_item_t efi_item;
- atomic_t efi_refcount;
+ refcount_t efi_refcount;
atomic_t efi_next_extent;
unsigned long efi_flags; /* misc flags */
xfs_efi_log_format_t efi_format;
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 0/5] fs, xfs atomic_t to refcount_t conversions version 2
@ 2017-03-01 8:47 Elena Reshetova
2017-03-01 8:47 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Elena Reshetova
0 siblings, 1 reply; 9+ messages in thread
From: Elena Reshetova @ 2017-03-01 8:47 UTC (permalink / raw)
To: linux-kernel
Cc: linux-xfs, peterz, gregkh, darrick.wong, david, Elena Reshetova
changes in v2:
* removed two patches that actually caused problems in testing and
there didn't seem to be a resonable way to convert them to refcount_t
based on all the triggered issues.
* run xfstests with TEST and SCRATCH partitions enabled, XFS_DEBUG on,
and WARNs on refcount_t API on. No issues found in the log upon execution.
Some random test failures (based on different runs) and stress tests do not always
pass, but again, no issues on refcounts noticed anywhere.
Now when new refcount_t type and API are finally merged
(see include/linux/refcount.h), the following
patches convert various refcounters in the fs/xfs susystem from atomic_t
to refcount_t. By doing this we prevent intentional or accidental
underflows or overflows that can led to use-after-free vulnerabilities.
The below patches are fully independent and can be cherry-picked separately.
Since we convert all kernel subsystems in the same fashion, resulting
in about 300 patches, we have to group them for sending at least in some
fashion to be manageable. Please excuse the long cc list.
Elena Reshetova (5):
fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to
refcount_t
fs, xfs: convert xlog_ticket.t_ref from atomic_t to refcount_t
fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to
refcount_t
fs, xfs: convert xfs_rui_log_item.rui_refcount from atomic_t to
refcount_t
fs/xfs/xfs_bmap_item.c | 4 ++--
fs/xfs/xfs_bmap_item.h | 4 +++-
fs/xfs/xfs_extfree_item.c | 4 ++--
fs/xfs/xfs_extfree_item.h | 4 +++-
fs/xfs/xfs_log.c | 10 +++++-----
fs/xfs/xfs_log_priv.h | 4 +++-
fs/xfs/xfs_refcount_item.c | 4 ++--
fs/xfs/xfs_refcount_item.h | 4 +++-
fs/xfs/xfs_rmap_item.c | 4 ++--
fs/xfs/xfs_rmap_item.h | 4 +++-
10 files changed, 28 insertions(+), 18 deletions(-)
--
2.7.4
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t
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 ` Elena Reshetova
0 siblings, 0 replies; 9+ messages in thread
From: Elena Reshetova @ 2017-03-01 8:47 UTC (permalink / raw)
To: linux-kernel
Cc: linux-xfs, peterz, gregkh, darrick.wong, david, Elena Reshetova,
Hans Liljestrand, Kees Cook, David Windsor
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_extfree_item.c | 4 ++--
fs/xfs/xfs_extfree_item.h | 4 +++-
2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
index d7bc149..4e0acf0 100644
--- a/fs/xfs/xfs_extfree_item.c
+++ b/fs/xfs/xfs_extfree_item.c
@@ -220,7 +220,7 @@ xfs_efi_init(
efip->efi_format.efi_nextents = nextents;
efip->efi_format.efi_id = (uintptr_t)(void *)efip;
atomic_set(&efip->efi_next_extent, 0);
- atomic_set(&efip->efi_refcount, 2);
+ refcount_set(&efip->efi_refcount, 2);
return efip;
}
@@ -290,7 +290,7 @@ void
xfs_efi_release(
struct xfs_efi_log_item *efip)
{
- if (atomic_dec_and_test(&efip->efi_refcount)) {
+ if (refcount_dec_and_test(&efip->efi_refcount)) {
xfs_trans_ail_remove(&efip->efi_item, SHUTDOWN_LOG_IO_ERROR);
xfs_efi_item_free(efip);
}
diff --git a/fs/xfs/xfs_extfree_item.h b/fs/xfs/xfs_extfree_item.h
index a32c794..e6da63d 100644
--- a/fs/xfs/xfs_extfree_item.h
+++ b/fs/xfs/xfs_extfree_item.h
@@ -18,6 +18,8 @@
#ifndef __XFS_EXTFREE_ITEM_H__
#define __XFS_EXTFREE_ITEM_H__
+#include <linux/refcount.h>
+
/* kernel only EFI/EFD definitions */
struct xfs_mount;
@@ -64,7 +66,7 @@ struct kmem_zone;
*/
typedef struct xfs_efi_log_item {
xfs_log_item_t efi_item;
- atomic_t efi_refcount;
+ refcount_t efi_refcount;
atomic_t efi_next_extent;
unsigned long efi_flags; /* misc flags */
xfs_efi_log_format_t efi_format;
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
end of thread, other threads:[~2017-11-29 11:38 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-11-29 11:37 [PATCH 0/5] v2 xfs refcount conversions Elena Reshetova
2017-11-29 11:37 ` [PATCH 1/5] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t Elena Reshetova
2017-11-29 11:38 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount " Elena Reshetova
2017-11-29 11:38 ` [PATCH 3/5] fs, xfs: convert xlog_ticket.t_ref " Elena Reshetova
2017-11-29 11:38 ` [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount " Elena Reshetova
2017-11-29 11:38 ` [PATCH 5/5] fs, xfs: convert xfs_rui_log_item.rui_refcount " Elena Reshetova
-- strict thread matches above, loose matches on Subject: below --
2017-10-20 11:07 [PATCH 0/5] xfs refcount conversions Elena Reshetova
2017-10-20 11:07 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Elena Reshetova
2017-03-08 8:53 [PATCH 0/5] fs, xfs refcount conversions Elena Reshetova
2017-03-08 8:53 ` [PATCH 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Elena Reshetova
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 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Elena Reshetova
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