[PATCH] procfs: Fix error handling of proc_register()

[PATCH] procfs: Fix error handling of proc_register()

[Debabrata Banerjee]

	I don't see why this should print warnings at all instead of properly
	unrolling allocations and returning an appropriate error. It's actually
	leaking resources currently.

to: Alexander Viro <viro@zeniv.linux.org.uk>
to: linux-kernel@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com>
---
 fs/proc/generic.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 317b726..89b20cc 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -304,6 +304,7 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
 		dp->proc_iops = &proc_file_inode_operations;
 	} else {
 		WARN_ON(1);
+		proc_free_inum(dp->low_ino);
 		return -EINVAL;
 	}
 
@@ -311,9 +312,13 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
 
 	for (tmp = dir->subdir; tmp; tmp = tmp->next)
 		if (strcmp(tmp->name, dp->name) == 0) {
-			WARN(1, "proc_dir_entry '%s/%s' already registered\n",
-				dir->name, dp->name);
-			break;
+			spin_unlock(&proc_subdir_lock);
+
+			if (S_ISDIR(dp->mode))
+				dir->nlink--;
+
+			proc_free_inum(dp->low_ino);
+			return -EEXIST;
 		}
 
 	dp->next = dir->subdir;
-- 
2.1.2

Re: [PATCH] procfs: Fix error handling of proc_register()

[Andrew Morton]

On Thu, 16 Oct 2014 16:46:02 -0400 Debabrata Banerjee <dbanerje@akamai.com> wrote:

> 	I don't see why this should print warnings at all instead of properly
> 	unrolling allocations and returning an appropriate error. It's actually
> 	leaking resources currently.

I think the warnings are useful - a duplicate name in /proc is a
significant kernel bug and we'll want to know precisely what caused it
and get it fixed up quickly.  So let's keep that bit.

> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -304,6 +304,7 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
>  		dp->proc_iops = &proc_file_inode_operations;
>  	} else {
>  		WARN_ON(1);
> +		proc_free_inum(dp->low_ino);
>  		return -EINVAL;
>  	}
>  
> @@ -311,9 +312,13 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
>  
>  	for (tmp = dir->subdir; tmp; tmp = tmp->next)
>  		if (strcmp(tmp->name, dp->name) == 0) {
> -			WARN(1, "proc_dir_entry '%s/%s' already registered\n",
> -				dir->name, dp->name);
> -			break;
> +			spin_unlock(&proc_subdir_lock);
> +
> +			if (S_ISDIR(dp->mode))
> +				dir->nlink--;
> +
> +			proc_free_inum(dp->low_ino);
> +			return -EEXIST;
>  		}

Your patch conflicts somewhat with Nicolas's "fs/proc: use a rb tree for
the directory entries".  Here's what I ended up with:



From: Debabrata Banerjee <dbanerje@akamai.com>
Subject: procfs: fix error handling of proc_register()

proc_register() error paths are leaking inodes and directory refcounts.

Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/generic.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff -puN fs/proc/generic.c~procfs-fix-error-handling-of-proc_register fs/proc/generic.c
--- a/fs/proc/generic.c~procfs-fix-error-handling-of-proc_register
+++ a/fs/proc/generic.c
@@ -369,14 +369,21 @@ static int proc_register(struct proc_dir
 		dp->proc_iops = &proc_file_inode_operations;
 	} else {
 		WARN_ON(1);
+		proc_free_inum(dp->low_ino);
 		return -EINVAL;
 	}
 
 	spin_lock(&proc_subdir_lock);
 	dp->parent = dir;
-	if (pde_subdir_insert(dir, dp) == false)
+	if (pde_subdir_insert(dir, dp) == false) {
 		WARN(1, "proc_dir_entry '%s/%s' already registered\n",
 		     dir->name, dp->name);
+		spin_unlock(&proc_subdir_lock);
+		if (S_ISDIR(dp->mode))
+			dir->nlink--;
+		proc_free_inum(dp->low_ino);
+		return -EEXIST;
+	}
 	spin_unlock(&proc_subdir_lock);
 
 	return 0;
_

Re: [PATCH] procfs: Fix error handling of proc_register()

[Nicolas Dichtel]

Le 23/10/2014 00:40, Andrew Morton a écrit :
> On Thu, 16 Oct 2014 16:46:02 -0400 Debabrata Banerjee <dbanerje@akamai.com> wrote:
>
>> 	I don't see why this should print warnings at all instead of properly
>> 	unrolling allocations and returning an appropriate error. It's actually
>> 	leaking resources currently.
>
> I think the warnings are useful - a duplicate name in /proc is a
> significant kernel bug and we'll want to know precisely what caused it
> and get it fixed up quickly.  So let's keep that bit.
>
>> --- a/fs/proc/generic.c
>> +++ b/fs/proc/generic.c
>> @@ -304,6 +304,7 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
>>   		dp->proc_iops = &proc_file_inode_operations;
>>   	} else {
>>   		WARN_ON(1);
>> +		proc_free_inum(dp->low_ino);
>>   		return -EINVAL;
>>   	}
>>
>> @@ -311,9 +312,13 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
>>
>>   	for (tmp = dir->subdir; tmp; tmp = tmp->next)
>>   		if (strcmp(tmp->name, dp->name) == 0) {
>> -			WARN(1, "proc_dir_entry '%s/%s' already registered\n",
>> -				dir->name, dp->name);
>> -			break;
>> +			spin_unlock(&proc_subdir_lock);
>> +
>> +			if (S_ISDIR(dp->mode))
>> +				dir->nlink--;
>> +
>> +			proc_free_inum(dp->low_ino);
>> +			return -EEXIST;
>>   		}
>
> Your patch conflicts somewhat with Nicolas's "fs/proc: use a rb tree for
> the directory entries".  Here's what I ended up with:
>
>
>
> From: Debabrata Banerjee <dbanerje@akamai.com>
> Subject: procfs: fix error handling of proc_register()
>
> proc_register() error paths are leaking inodes and directory refcounts.
>
> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
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