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SubjectRe: [Ocfs2-devel] [PATCH 1/3 v2] fs: ocfs2: Fix possible null-pointer dereferences in ocfs2_xa_prepare_entry()
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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
>>
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> Ocfs2-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel

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