[PATCH 1/3 v2] fs: ocfs2: Fix possible null-pointer dereferences in ocfs2_xa_prepare_entry()

[PATCH 1/3 v2] fs: ocfs2: Fix possible null-pointer dereferences in ocfs2_xa_prepare_entry()

[Jia-Ju Bai]

In ocfs2_xa_prepare_entry(), there is an if statement on line 2136 to
check whether loc->xl_entry is NULL:
    if (loc->xl_entry)

When loc->xl_entry is NULL, it is used on line 2158:
    ocfs2_xa_add_entry(loc, name_hash);
        loc->xl_entry->xe_name_hash = cpu_to_le32(name_hash);
        loc->xl_entry->xe_name_offset = cpu_to_le16(loc->xl_size);
and line 2164:
    ocfs2_xa_add_namevalue(loc, xi);
        loc->xl_entry->xe_value_size = cpu_to_le64(xi->xi_value_len);
        loc->xl_entry->xe_name_len = xi->xi_name_len;

Thus, possible null-pointer dereferences may occur.

To fix these bugs, if loc-xl_entry is NULL, ocfs2_xa_prepare_entry()
abnormally returns with -EINVAL.

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
v2:
* Directly return -EINVAL if loc-xl_entry is NULL.
  Thank Joseph for helpful advice.

---
 fs/ocfs2/xattr.c | 44 +++++++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 385f3aaa2448..4b876c82a35c 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -2133,29 +2133,31 @@ static int ocfs2_xa_prepare_entry(struct ocfs2_xa_loc *loc,
 	if (rc)
 		goto out;
 
-	if (loc->xl_entry) {
-		if (ocfs2_xa_can_reuse_entry(loc, xi)) {
-			orig_value_size = loc->xl_entry->xe_value_size;
-			rc = ocfs2_xa_reuse_entry(loc, xi, ctxt);
-			if (rc)
-				goto out;
-			goto alloc_value;
-		}
+	if (!loc->xl_entry) {
+		rc = -EINVAL;
+		goto out;
+	}
 
-		if (!ocfs2_xattr_is_local(loc->xl_entry)) {
-			orig_clusters = ocfs2_xa_value_clusters(loc);
-			rc = ocfs2_xa_value_truncate(loc, 0, ctxt);
-			if (rc) {
-				mlog_errno(rc);
-				ocfs2_xa_cleanup_value_truncate(loc,
-								"overwriting",
-								orig_clusters);
-				goto out;
-			}
+	if (ocfs2_xa_can_reuse_entry(loc, xi)) {
+		orig_value_size = loc->xl_entry->xe_value_size;
+		rc = ocfs2_xa_reuse_entry(loc, xi, ctxt);
+		if (rc)
+			goto out;
+		goto alloc_value;
+	}
+
+	if (!ocfs2_xattr_is_local(loc->xl_entry)) {
+		orig_clusters = ocfs2_xa_value_clusters(loc);
+		rc = ocfs2_xa_value_truncate(loc, 0, ctxt);
+		if (rc) {
+			mlog_errno(rc);
+			ocfs2_xa_cleanup_value_truncate(loc,
+							"overwriting",
+							orig_clusters);
+			goto out;
 		}
-		ocfs2_xa_wipe_namevalue(loc);
-	} else
-		ocfs2_xa_add_entry(loc, name_hash);
+	}
+	ocfs2_xa_wipe_namevalue(loc);
 
 	/*
 	 * If we get here, we have a blank entry.  Fill it.  We grow our
-- 
2.17.0

Re: [PATCH 1/3 v2] fs: ocfs2: Fix possible null-pointer dereferences in ocfs2_xa_prepare_entry()

[Joseph Qi]

On 19/7/26 18:14, Jia-Ju Bai wrote:
> In ocfs2_xa_prepare_entry(), there is an if statement on line 2136 to
> check whether loc->xl_entry is NULL:
>     if (loc->xl_entry)
> 
> When loc->xl_entry is NULL, it is used on line 2158:
>     ocfs2_xa_add_entry(loc, name_hash);
>         loc->xl_entry->xe_name_hash = cpu_to_le32(name_hash);
>         loc->xl_entry->xe_name_offset = cpu_to_le16(loc->xl_size);
> and line 2164:
>     ocfs2_xa_add_namevalue(loc, xi);
>         loc->xl_entry->xe_value_size = cpu_to_le64(xi->xi_value_len);
>         loc->xl_entry->xe_name_len = xi->xi_name_len;
> 
> Thus, possible null-pointer dereferences may occur.
> 
> To fix these bugs, if loc-xl_entry is NULL, ocfs2_xa_prepare_entry()
> abnormally returns with -EINVAL.
> 
> These bugs are found by a static analysis tool STCheck written by us.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>

Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> ---
> v2:
> * Directly return -EINVAL if loc-xl_entry is NULL.
>   Thank Joseph for helpful advice.
> 
> ---
>  fs/ocfs2/xattr.c | 44 +++++++++++++++++++++++---------------------
>  1 file changed, 23 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 385f3aaa2448..4b876c82a35c 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -2133,29 +2133,31 @@ static int ocfs2_xa_prepare_entry(struct ocfs2_xa_loc *loc,
>  	if (rc)
>  		goto out;
>  
> -	if (loc->xl_entry) {
> -		if (ocfs2_xa_can_reuse_entry(loc, xi)) {
> -			orig_value_size = loc->xl_entry->xe_value_size;
> -			rc = ocfs2_xa_reuse_entry(loc, xi, ctxt);
> -			if (rc)
> -				goto out;
> -			goto alloc_value;
> -		}
> +	if (!loc->xl_entry) {
> +		rc = -EINVAL;
> +		goto out;
> +	}
>  
> -		if (!ocfs2_xattr_is_local(loc->xl_entry)) {
> -			orig_clusters = ocfs2_xa_value_clusters(loc);
> -			rc = ocfs2_xa_value_truncate(loc, 0, ctxt);
> -			if (rc) {
> -				mlog_errno(rc);
> -				ocfs2_xa_cleanup_value_truncate(loc,
> -								"overwriting",
> -								orig_clusters);
> -				goto out;
> -			}
> +	if (ocfs2_xa_can_reuse_entry(loc, xi)) {
> +		orig_value_size = loc->xl_entry->xe_value_size;
> +		rc = ocfs2_xa_reuse_entry(loc, xi, ctxt);
> +		if (rc)
> +			goto out;
> +		goto alloc_value;
> +	}
> +
> +	if (!ocfs2_xattr_is_local(loc->xl_entry)) {
> +		orig_clusters = ocfs2_xa_value_clusters(loc);
> +		rc = ocfs2_xa_value_truncate(loc, 0, ctxt);
> +		if (rc) {
> +			mlog_errno(rc);
> +			ocfs2_xa_cleanup_value_truncate(loc,
> +							"overwriting",
> +							orig_clusters);
> +			goto out;
>  		}
> -		ocfs2_xa_wipe_namevalue(loc);
> -	} else
> -		ocfs2_xa_add_entry(loc, name_hash);
> +	}
> +	ocfs2_xa_wipe_namevalue(loc);
>  
>  	/*
>  	 * If we get here, we have a blank entry.  Fill it.  We grow our
> 

Re: [Ocfs2-devel] [PATCH 1/3 v2] fs: ocfs2: Fix possible null-pointer dereferences in ocfs2_xa_prepare_entry()

[Changwei Ge]

Hi Jia-Ju,


Please checkout my comments inline.


On 2019/7/27 8:49 上午, Joseph Qi wrote:
>
> On 19/7/26 18:14, Jia-Ju Bai wrote:
>> In ocfs2_xa_prepare_entry(), there is an if statement on line 2136 to
>> check whether loc->xl_entry is NULL:
>>      if (loc->xl_entry)
>>
>> When loc->xl_entry is NULL, it is used on line 2158:
>>      ocfs2_xa_add_entry(loc, name_hash);

This won't deference a NULL ->xl_entry because ->xlo_add_entry() is 
already called to whether ocfs2_xa_block_add_entry() or 
ocfs2_xa_bucket_add_entry()

 From the function name we can tell the intention it wants to add entry 
so of course it should be NULL before calling it.


Thanks,

Changwei


>>          loc->xl_entry->xe_name_hash = cpu_to_le32(name_hash);
>>          loc->xl_entry->xe_name_offset = cpu_to_le16(loc->xl_size);
>> and line 2164:
>>      ocfs2_xa_add_namevalue(loc, xi);
>>          loc->xl_entry->xe_value_size = cpu_to_le64(xi->xi_value_len);
>>          loc->xl_entry->xe_name_len = xi->xi_name_len;
>>
>> Thus, possible null-pointer dereferences may occur.
>>
>> To fix these bugs, if loc-xl_entry is NULL, ocfs2_xa_prepare_entry()
>> abnormally returns with -EINVAL.
>>
>> These bugs are found by a static analysis tool STCheck written by us.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
>> ---
>> v2:
>> * Directly return -EINVAL if loc-xl_entry is NULL.
>>    Thank Joseph for helpful advice.
>>
>> ---
>>   fs/ocfs2/xattr.c | 44 +++++++++++++++++++++++---------------------
>>   1 file changed, 23 insertions(+), 21 deletions(-)
>>
>> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
>> index 385f3aaa2448..4b876c82a35c 100644
>> --- a/fs/ocfs2/xattr.c
>> +++ b/fs/ocfs2/xattr.c
>> @@ -2133,29 +2133,31 @@ static int ocfs2_xa_prepare_entry(struct ocfs2_xa_loc *loc,
>>   	if (rc)
>>   		goto out;
>>   
>> -	if (loc->xl_entry) {
>> -		if (ocfs2_xa_can_reuse_entry(loc, xi)) {
>> -			orig_value_size = loc->xl_entry->xe_value_size;
>> -			rc = ocfs2_xa_reuse_entry(loc, xi, ctxt);
>> -			if (rc)
>> -				goto out;
>> -			goto alloc_value;
>> -		}
>> +	if (!loc->xl_entry) {
>> +		rc = -EINVAL;
>> +		goto out;
>> +	}
>>   
>> -		if (!ocfs2_xattr_is_local(loc->xl_entry)) {
>> -			orig_clusters = ocfs2_xa_value_clusters(loc);
>> -			rc = ocfs2_xa_value_truncate(loc, 0, ctxt);
>> -			if (rc) {
>> -				mlog_errno(rc);
>> -				ocfs2_xa_cleanup_value_truncate(loc,
>> -								"overwriting",
>> -								orig_clusters);
>> -				goto out;
>> -			}
>> +	if (ocfs2_xa_can_reuse_entry(loc, xi)) {
>> +		orig_value_size = loc->xl_entry->xe_value_size;
>> +		rc = ocfs2_xa_reuse_entry(loc, xi, ctxt);
>> +		if (rc)
>> +			goto out;
>> +		goto alloc_value;
>> +	}
>> +
>> +	if (!ocfs2_xattr_is_local(loc->xl_entry)) {
>> +		orig_clusters = ocfs2_xa_value_clusters(loc);
>> +		rc = ocfs2_xa_value_truncate(loc, 0, ctxt);
>> +		if (rc) {
>> +			mlog_errno(rc);
>> +			ocfs2_xa_cleanup_value_truncate(loc,
>> +							"overwriting",
>> +							orig_clusters);
>> +			goto out;
>>   		}
>> -		ocfs2_xa_wipe_namevalue(loc);
>> -	} else
>> -		ocfs2_xa_add_entry(loc, name_hash);
>> +	}
>> +	ocfs2_xa_wipe_namevalue(loc);
>>   
>>   	/*
>>   	 * If we get here, we have a blank entry.  Fill it.  We grow our
>>
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel

Re: [1/3 v2] ocfs2: Fix possible null-pointer dereferences in ocfs2_xa_prepare_entry()

[Markus Elfring]

> These bugs are found by a static analysis tool STCheck written by us.

Would you like to improve any more commit descriptions also by
adjusting such a wording?

Regards,
Markus