* [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init
@ 2023-12-07 3:43 Dinghao Liu
2023-12-07 15:43 ` Dave Jiang
0 siblings, 1 reply; 6+ messages in thread
From: Dinghao Liu @ 2023-12-07 3:43 UTC (permalink / raw)
To: dinghao.liu
Cc: Vishal Verma, Dan Williams, Dave Jiang, Ira Weiny, nvdimm, linux-kernel
When an error happens in btt_freelist_init(), its caller
discover_arenas() will directly free arena, which makes
arena->freelist allocated in btt_freelist_init() a leaked
memory. Fix this by freeing arena->freelist in all error
handling paths of btt_freelist_init().
Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
---
drivers/nvdimm/btt.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index d5593b0dc700..d8c4ba8bfdda 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -544,8 +544,10 @@ static int btt_freelist_init(struct arena_info *arena)
for (i = 0; i < arena->nfree; i++) {
new = btt_log_read(arena, i, &log_new, LOG_NEW_ENT);
- if (new < 0)
- return new;
+ if (new < 0) {
+ ret = new;
+ goto out_free;
+ }
/* old and new map entries with any flags stripped out */
log_oldmap = ent_lba(le32_to_cpu(log_new.old_map));
@@ -577,7 +579,7 @@ static int btt_freelist_init(struct arena_info *arena)
ret = btt_map_read(arena, le32_to_cpu(log_new.lba), &map_entry,
NULL, NULL, 0);
if (ret)
- return ret;
+ goto out_free;
/*
* The map_entry from btt_read_map is stripped of any flag bits,
@@ -594,11 +596,16 @@ static int btt_freelist_init(struct arena_info *arena)
ret = btt_map_write(arena, le32_to_cpu(log_new.lba),
le32_to_cpu(log_new.new_map), 0, 0, 0);
if (ret)
- return ret;
+ goto out_free;
}
}
return 0;
+
+out_free:
+ kfree(arena->freelist);
+ arena->freelist = NULL;
+ return ret;
}
static bool ent_is_padding(struct log_entry *ent)
--
2.17.1
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init
2023-12-07 3:43 [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init Dinghao Liu
@ 2023-12-07 15:43 ` Dave Jiang
2023-12-07 20:46 ` Ira Weiny
0 siblings, 1 reply; 6+ messages in thread
From: Dave Jiang @ 2023-12-07 15:43 UTC (permalink / raw)
To: Dinghao Liu; +Cc: Vishal Verma, Dan Williams, Ira Weiny, nvdimm, linux-kernel
On 12/6/23 20:43, Dinghao Liu wrote:
> When an error happens in btt_freelist_init(), its caller
> discover_arenas() will directly free arena, which makes
> arena->freelist allocated in btt_freelist_init() a leaked
> memory. Fix this by freeing arena->freelist in all error
> handling paths of btt_freelist_init().
>
> Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
> Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
How about use the new scope based resource management and we can avoid the goto mess altogether?
https://lwn.net/Articles/934679/
> ---
> drivers/nvdimm/btt.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
> index d5593b0dc700..d8c4ba8bfdda 100644
> --- a/drivers/nvdimm/btt.c
> +++ b/drivers/nvdimm/btt.c
> @@ -544,8 +544,10 @@ static int btt_freelist_init(struct arena_info *arena)
>
> for (i = 0; i < arena->nfree; i++) {
> new = btt_log_read(arena, i, &log_new, LOG_NEW_ENT);
> - if (new < 0)
> - return new;
> + if (new < 0) {
> + ret = new;
> + goto out_free;
> + }
>
> /* old and new map entries with any flags stripped out */
> log_oldmap = ent_lba(le32_to_cpu(log_new.old_map));
> @@ -577,7 +579,7 @@ static int btt_freelist_init(struct arena_info *arena)
> ret = btt_map_read(arena, le32_to_cpu(log_new.lba), &map_entry,
> NULL, NULL, 0);
> if (ret)
> - return ret;
> + goto out_free;
>
> /*
> * The map_entry from btt_read_map is stripped of any flag bits,
> @@ -594,11 +596,16 @@ static int btt_freelist_init(struct arena_info *arena)
> ret = btt_map_write(arena, le32_to_cpu(log_new.lba),
> le32_to_cpu(log_new.new_map), 0, 0, 0);
> if (ret)
> - return ret;
> + goto out_free;
> }
> }
>
> return 0;
> +
> +out_free:
> + kfree(arena->freelist);
> + arena->freelist = NULL;
> + return ret;
> }
>
> static bool ent_is_padding(struct log_entry *ent)
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init
2023-12-07 15:43 ` Dave Jiang
@ 2023-12-07 20:46 ` Ira Weiny
2023-12-08 6:35 ` dinghao.liu
0 siblings, 1 reply; 6+ messages in thread
From: Ira Weiny @ 2023-12-07 20:46 UTC (permalink / raw)
To: Dave Jiang, Dinghao Liu
Cc: Vishal Verma, Dan Williams, Ira Weiny, nvdimm, linux-kernel
Dave Jiang wrote:
>
[snip]
First off thanks for the patch. This code seems to have a few things to
clean up.
>
> On 12/6/23 20:43, Dinghao Liu wrote:
> > When an error happens in btt_freelist_init(), its caller
> > discover_arenas() will directly free arena, which makes
> > arena->freelist allocated in btt_freelist_init() a leaked
> > memory. Fix this by freeing arena->freelist in all error
> > handling paths of btt_freelist_init().
> >
> > Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
> > Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
>
> How about use the new scope based resource management and we can avoid the goto mess altogether?
> https://lwn.net/Articles/934679/
>
The freelist is returned as part of arena. I've not traced both paths of
btt_freelist_init() completely but devm_kcalloc() looks like a better
solution here because this memory needs to live past the function scope.
That said, this patch does not completely fix freelist from leaking in the
following error path.
discover_arenas()
btt_freelist_init() -> ok (memory allocated)
btt_rtt_init() -> fail
goto out;
(leak because arena is not yet on btt->arena_list)
OR
btt_maplocks_init() -> fail
goto out;
(leak because arena is not yet on btt->arena_list)
This error could be fixed by adding to arena_list earlier but devm_*()
also takes care of this without having to worry about that logic.
On normal operation all of this memory can be free'ed with the
corresponding devm_kfree() and/or devm_add_action_*() calls if arenas come
and go. I'm not sure off the top of my head.
In addition, looking at this code. discover_arenas() could make use of
the scoped based management for struct btt_sb *super!
Dinghao would you be willing to submit a series of 2 or 3 patches to fix
the above issues?
Thanks!
Ira
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init
2023-12-07 20:46 ` Ira Weiny
@ 2023-12-08 6:35 ` dinghao.liu
2023-12-08 23:01 ` Ira Weiny
0 siblings, 1 reply; 6+ messages in thread
From: dinghao.liu @ 2023-12-08 6:35 UTC (permalink / raw)
To: Ira Weiny; +Cc: Dave Jiang, Vishal Verma, Dan Williams, nvdimm, linux-kernel
> Dave Jiang wrote:
> >
>
> [snip]
>
> First off thanks for the patch. This code seems to have a few things to
> clean up.
>
> >
> > On 12/6/23 20:43, Dinghao Liu wrote:
> > > When an error happens in btt_freelist_init(), its caller
> > > discover_arenas() will directly free arena, which makes
> > > arena->freelist allocated in btt_freelist_init() a leaked
> > > memory. Fix this by freeing arena->freelist in all error
> > > handling paths of btt_freelist_init().
> > >
> > > Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
> > > Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> >
> > How about use the new scope based resource management and we can avoid the goto mess altogether?
> > https://lwn.net/Articles/934679/
> >
>
> The freelist is returned as part of arena. I've not traced both paths of
> btt_freelist_init() completely but devm_kcalloc() looks like a better
> solution here because this memory needs to live past the function scope.
>
> That said, this patch does not completely fix freelist from leaking in the
> following error path.
>
> discover_arenas()
> btt_freelist_init() -> ok (memory allocated)
> btt_rtt_init() -> fail
> goto out;
> (leak because arena is not yet on btt->arena_list)
> OR
> btt_maplocks_init() -> fail
> goto out;
> (leak because arena is not yet on btt->arena_list)
>
Thanks for pointing out this issue! I rechecked discover_arenas() and found
that btt_rtt_init() may also trigger a memleak for the same reason as
btt_freelist_init(). Also, I checked another call trace:
btt_init() -> btt_meta_init() -> btt_maplocks_init()
I think there is a memleak if btt_maplocks_init() succeeds but an error
happens in btt_init() after btt_meta_init() (e.g., when btt_blk_init()
returns an error). Therefore, we may need to fix three functions.
> This error could be fixed by adding to arena_list earlier but devm_*()
> also takes care of this without having to worry about that logic.
>
> On normal operation all of this memory can be free'ed with the
> corresponding devm_kfree() and/or devm_add_action_*() calls if arenas come
> and go. I'm not sure off the top of my head.
>
> In addition, looking at this code. discover_arenas() could make use of
> the scoped based management for struct btt_sb *super!
>
> Dinghao would you be willing to submit a series of 2 or 3 patches to fix
> the above issues?
>
Sure. Currently I plan to send 2 patches as follows:
1. Using devm_kcalloc() to replace kcalloc() in btt_freelist_init(),
btt_rtt_init(), and btt_maplocks_init(), and removing the corresponding
kfree in free_arenas(). I checked some uses of devm_kcalloc() and it
seems that we need not to call devm_kfree(). The memory is automatically
freed on driver detach, right?
2. Using the scoped based management for struct btt_sb *super (not a bug,
but it could improve the code).
I'm not quite sure whether my understanding or bug fixing plan is correct.
If there are any issues, please correct me, thanks!
Regards,
Dinghao
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init
2023-12-08 6:35 ` dinghao.liu
@ 2023-12-08 23:01 ` Ira Weiny
2023-12-09 16:27 ` dinghao.liu
0 siblings, 1 reply; 6+ messages in thread
From: Ira Weiny @ 2023-12-08 23:01 UTC (permalink / raw)
To: dinghao.liu, Ira Weiny
Cc: Dave Jiang, Vishal Verma, Dan Williams, nvdimm, linux-kernel
dinghao.liu@ wrote:
> > Dave Jiang wrote:
[snip]
> > That said, this patch does not completely fix freelist from leaking in the
> > following error path.
> >
> > discover_arenas()
> > btt_freelist_init() -> ok (memory allocated)
> > btt_rtt_init() -> fail
> > goto out;
> > (leak because arena is not yet on btt->arena_list)
> > OR
> > btt_maplocks_init() -> fail
> > goto out;
> > (leak because arena is not yet on btt->arena_list)
> >
>
> Thanks for pointing out this issue! I rechecked discover_arenas() and found
> that btt_rtt_init() may also trigger a memleak for the same reason as
> btt_freelist_init(). Also, I checked another call trace:
>
> btt_init() -> btt_meta_init() -> btt_maplocks_init()
>
> I think there is a memleak if btt_maplocks_init() succeeds but an error
> happens in btt_init() after btt_meta_init() (e.g., when btt_blk_init()
> returns an error). Therefore, we may need to fix three functions.
Yea I think we need to trace this code better. This is why devm_ is nice for
memory allocated for the life of the device.
>
> > This error could be fixed by adding to arena_list earlier but devm_*()
> > also takes care of this without having to worry about that logic.
> >
> > On normal operation all of this memory can be free'ed with the
> > corresponding devm_kfree() and/or devm_add_action_*() calls if arenas come
> > and go. I'm not sure off the top of my head.
> >
> > In addition, looking at this code. discover_arenas() could make use of
> > the scoped based management for struct btt_sb *super!
> >
> > Dinghao would you be willing to submit a series of 2 or 3 patches to fix
> > the above issues?
> >
>
> Sure. Currently I plan to send 2 patches as follows:
> 1. Using devm_kcalloc() to replace kcalloc() in btt_freelist_init(),
> btt_rtt_init(), and btt_maplocks_init(), and removing the corresponding
> kfree in free_arenas(). I checked some uses of devm_kcalloc() and it
> seems that we need not to call devm_kfree(). The memory is automatically
> freed on driver detach, right?
On device put yes. So if these allocations are scoped to the life of the
device there would be no reason to call devm_kfree() on them at all. I was not
sure if they got reallocated at some point or not.
> 2. Using the scoped based management for struct btt_sb *super (not a bug,
> but it could improve the code).
Good!
>
> I'm not quite sure whether my understanding or bug fixing plan is correct.
> If there are any issues, please correct me, thanks!
The above sounds right.
Ira
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init
2023-12-08 23:01 ` Ira Weiny
@ 2023-12-09 16:27 ` dinghao.liu
0 siblings, 0 replies; 6+ messages in thread
From: dinghao.liu @ 2023-12-09 16:27 UTC (permalink / raw)
To: Ira Weiny; +Cc: Dave Jiang, Vishal Verma, Dan Williams, nvdimm, linux-kernel
> dinghao.liu@ wrote:
> > > Dave Jiang wrote:
>
> [snip]
>
> > > That said, this patch does not completely fix freelist from leaking in the
> > > following error path.
> > >
> > > discover_arenas()
> > > btt_freelist_init() -> ok (memory allocated)
> > > btt_rtt_init() -> fail
> > > goto out;
> > > (leak because arena is not yet on btt->arena_list)
> > > OR
> > > btt_maplocks_init() -> fail
> > > goto out;
> > > (leak because arena is not yet on btt->arena_list)
> > >
> >
> > Thanks for pointing out this issue! I rechecked discover_arenas() and found
> > that btt_rtt_init() may also trigger a memleak for the same reason as
> > btt_freelist_init(). Also, I checked another call trace:
> >
> > btt_init() -> btt_meta_init() -> btt_maplocks_init()
> >
> > I think there is a memleak if btt_maplocks_init() succeeds but an error
> > happens in btt_init() after btt_meta_init() (e.g., when btt_blk_init()
> > returns an error). Therefore, we may need to fix three functions.
>
> Yea I think we need to trace this code better. This is why devm_ is nice for
> memory allocated for the life of the device.
>
> >
> > > This error could be fixed by adding to arena_list earlier but devm_*()
> > > also takes care of this without having to worry about that logic.
> > >
> > > On normal operation all of this memory can be free'ed with the
> > > corresponding devm_kfree() and/or devm_add_action_*() calls if arenas come
> > > and go. I'm not sure off the top of my head.
> > >
> > > In addition, looking at this code. discover_arenas() could make use of
> > > the scoped based management for struct btt_sb *super!
> > >
> > > Dinghao would you be willing to submit a series of 2 or 3 patches to fix
> > > the above issues?
> > >
> >
> > Sure. Currently I plan to send 2 patches as follows:
> > 1. Using devm_kcalloc() to replace kcalloc() in btt_freelist_init(),
> > btt_rtt_init(), and btt_maplocks_init(), and removing the corresponding
> > kfree in free_arenas(). I checked some uses of devm_kcalloc() and it
> > seems that we need not to call devm_kfree(). The memory is automatically
> > freed on driver detach, right?
>
> On device put yes. So if these allocations are scoped to the life of the
> device there would be no reason to call devm_kfree() on them at all. I was not
> sure if they got reallocated at some point or not.
>
> > 2. Using the scoped based management for struct btt_sb *super (not a bug,
> > but it could improve the code).
>
> Good!
>
> >
> > I'm not quite sure whether my understanding or bug fixing plan is correct.
> > If there are any issues, please correct me, thanks!
>
> The above sounds right.
> Ira
Thanks for the review! I will send the patches soon.
Regards,
Dinghao
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-12-09 16:27 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2023-12-07 3:43 [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init Dinghao Liu
2023-12-07 15:43 ` Dave Jiang
2023-12-07 20:46 ` Ira Weiny
2023-12-08 6:35 ` dinghao.liu
2023-12-08 23:01 ` Ira Weiny
2023-12-09 16:27 ` dinghao.liu
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