[PATCH] hfs: fix a memleak in hfs_find_init

[PATCH] hfs: fix a memleak in hfs_find_init

[Zhipeng Lu]

When the switch statment goes to default and return an error, ptr should
be freed since it is allocated in hfs_find_init.

Fixes: b3b2177a2d79 ("hfs: add lock nesting notation to hfs_find_init")
Signed-off-by: Zhipeng Lu <alexious@zju.edu.cn>
---
 fs/hfs/bfind.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/hfs/bfind.c b/fs/hfs/bfind.c
index ef9498a6e88a..7aa3b9aba4d1 100644
--- a/fs/hfs/bfind.c
+++ b/fs/hfs/bfind.c
@@ -36,6 +36,7 @@ int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
 		mutex_lock_nested(&tree->tree_lock, ATTR_BTREE_MUTEX);
 		break;
 	default:
+		kfree(fd->search_key);
 		return -EINVAL;
 	}
 	return 0;
-- 
2.34.1

Re: [PATCH] hfs: fix a memleak in hfs_find_init

[Viacheslav Dubeyko]

> On 22 Jan 2024, at 20:27, Zhipeng Lu <alexious@zju.edu.cn> wrote:
> 
> When the switch statment goes to default and return an error, ptr should
> be freed since it is allocated in hfs_find_init.
> 

Do you have any memory leaks report? Could you share it in the comments?
Which use-case reproduces the issue? It will be easier to review the fix
If you can share the path of reproduction.

Thanks,
Slava.

> Fixes: b3b2177a2d79 ("hfs: add lock nesting notation to hfs_find_init")
> Signed-off-by: Zhipeng Lu <alexious@zju.edu.cn>
> ---
> fs/hfs/bfind.c | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/fs/hfs/bfind.c b/fs/hfs/bfind.c
> index ef9498a6e88a..7aa3b9aba4d1 100644
> --- a/fs/hfs/bfind.c
> +++ b/fs/hfs/bfind.c
> @@ -36,6 +36,7 @@ int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
> mutex_lock_nested(&tree->tree_lock, ATTR_BTREE_MUTEX);
> break;
> default:
> + kfree(fd->search_key);
> return -EINVAL;
> }
> return 0;
> -- 
> 2.34.1
> 

Re: [PATCH] hfs: fix a memleak in hfs_find_init

[alexious]

> > On 22 Jan 2024, at 20:27, Zhipeng Lu <alexious@zju.edu.cn> wrote:
> > 
> > When the switch statment goes to default and return an error, ptr should
> > be freed since it is allocated in hfs_find_init.
> > 
> 
> Do you have any memory leaks report? Could you share it in the comments?
> Which use-case reproduces the issue? It will be easier to review the fix
> If you can share the path of reproduction.
> 
> Thanks,
> Slava.

Well, we found this potential memory leak by static analysis.

We found that all of hfs_find_init's callers won't release `ptr` when 
hfs_find_init fails, while they will do release `ptr` when functions 
that after hfs_find_init fails. This tactic observation suggests that
hfs_find_init proberly should release `ptr` when it fails, i.e. in the
default branch of switch in this patch.

Besides, we noticed another implementation of hfs_find_init in 
fs/hfsplus/bfind.c, which is essentially identical to the one in 
this patch (in fs/hfs/bfind.c) but calling `BUG();` in default branch
to trigger an error-handling.

Thanks,
Zhipeng.


> 
> > Fixes: b3b2177a2d79 ("hfs: add lock nesting notation to hfs_find_init")
> > Signed-off-by: Zhipeng Lu <alexious@zju.edu.cn>
> > ---
> > fs/hfs/bfind.c | 1 +
> > 1 file changed, 1 insertion(+)
> > 
> > diff --git a/fs/hfs/bfind.c b/fs/hfs/bfind.c
> > index ef9498a6e88a..7aa3b9aba4d1 100644
> > --- a/fs/hfs/bfind.c
> > +++ b/fs/hfs/bfind.c
> > @@ -36,6 +36,7 @@ int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
> > mutex_lock_nested(&tree->tree_lock, ATTR_BTREE_MUTEX);
> > break;
> > default:
> > + kfree(fd->search_key);
> > return -EINVAL;
> > }
> > return 0;
> > -- 
> > 2.34.1
> > 

Re: [PATCH] hfs: fix a memleak in hfs_find_init

[Viacheslav Dubeyko]

> On 29 Jan 2024, at 15:54, alexious@zju.edu.cn wrote:
> 
>>> On 22 Jan 2024, at 20:27, Zhipeng Lu <alexious@zju.edu.cn> wrote:
>>> 
>>> When the switch statment goes to default and return an error, ptr should
>>> be freed since it is allocated in hfs_find_init.
>>> 
>> 
>> Do you have any memory leaks report? Could you share it in the comments?
>> Which use-case reproduces the issue? It will be easier to review the fix
>> If you can share the path of reproduction.
>> 
>> Thanks,
>> Slava.
> 
> Well, we found this potential memory leak by static analysis.
> 
> We found that all of hfs_find_init's callers won't release `ptr` when 
> hfs_find_init fails, while they will do release `ptr` when functions 
> that after hfs_find_init fails. This tactic observation suggests that
> hfs_find_init proberly should release `ptr` when it fails, i.e. in the
> default branch of switch in this patch.
> 
> Besides, we noticed another implementation of hfs_find_init in 
> fs/hfsplus/bfind.c, which is essentially identical to the one in 
> this patch (in fs/hfs/bfind.c) but calling `BUG();` in default branch
> to trigger an error-handling.
> 

I see. I believe it makes sense to add all of this explanation
into comment section. Modification looks good. Mostly, hfs_find_exit()
does freeing resources and if hfs_find_init() fails, then hfs_find_exit()
is never called. Maybe, it makes sense to set fd->tree = NULL too but
it is not critical, as far as I can see.

Could you please rework the comment section of the patch?

Thanks,
Slava.

Re: [PATCH] hfs: fix a memleak in hfs_find_init

[alexious]

> > On 29 Jan 2024, at 15:54, alexious@zju.edu.cn wrote:
> > 
> >>> On 22 Jan 2024, at 20:27, Zhipeng Lu <alexious@zju.edu.cn> wrote:
> >>> 
> >>> When the switch statment goes to default and return an error, ptr should
> >>> be freed since it is allocated in hfs_find_init.
> >>> 
> >> 
> >> Do you have any memory leaks report? Could you share it in the comments?
> >> Which use-case reproduces the issue? It will be easier to review the fix
> >> If you can share the path of reproduction.
> >> 
> >> Thanks,
> >> Slava.
> > 
> > Well, we found this potential memory leak by static analysis.
> > 
> > We found that all of hfs_find_init's callers won't release `ptr` when 
> > hfs_find_init fails, while they will do release `ptr` when functions 
> > that after hfs_find_init fails. This tactic observation suggests that
> > hfs_find_init proberly should release `ptr` when it fails, i.e. in the
> > default branch of switch in this patch.
> > 
> > Besides, we noticed another implementation of hfs_find_init in 
> > fs/hfsplus/bfind.c, which is essentially identical to the one in 
> > this patch (in fs/hfs/bfind.c) but calling `BUG();` in default branch
> > to trigger an error-handling.
> > 
> 
> I see. I believe it makes sense to add all of this explanation
> into comment section. Modification looks good. Mostly, hfs_find_exit()
> does freeing resources and if hfs_find_init() fails, then hfs_find_exit()
> is never called. Maybe, it makes sense to set fd->tree = NULL too but
> it is not critical, as far as I can see.
> 
> Could you please rework the comment section of the patch? 

Sure, I'll including such idea in this patch and send a v2 version of 
this patch.

Thanks,
Zhipeng.

> Thanks,
> Slava.