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([2402:f000:4:72:808::177e]) by smtp.gmail.com with ESMTPSA id s67sm53345975pjb.8.2019.07.26.02.50.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Jul 2019 02:50:06 -0700 (PDT) Subject: Re: [PATCH 1/3] fs: ocfs2: Fix possible null-pointer dereferences in ocfs2_xa_prepare_entry() To: Joseph Qi , mark@fasheh.com, jlbec@evilplan.org Cc: ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org References: <20190726033655.32253-1-baijiaju1990@gmail.com> From: Jia-Ju Bai Message-ID: <620ac436-ffbc-8429-b952-278cd2a8aaba@gmail.com> Date: Fri, 26 Jul 2019 17:50:06 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/7/26 17:37, Joseph Qi wrote: > > On 19/7/26 11:36, 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 >> --- >> fs/ocfs2/xattr.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c >> index 385f3aaa2448..f690502daf3c 100644 >> --- a/fs/ocfs2/xattr.c >> +++ b/fs/ocfs2/xattr.c >> @@ -2154,8 +2154,10 @@ static int ocfs2_xa_prepare_entry(struct ocfs2_xa_loc *loc, >> } >> } >> ocfs2_xa_wipe_namevalue(loc); >> - } else >> - ocfs2_xa_add_entry(loc, name_hash); >> + } else { >> + rc = -EINVAL; >> + goto out; >> + } > Since entry not found, so there is nothing to do in > ocfs2_xa_prepare_entry(). We may change it like: > > if (!loc->xl_entry) { > rc = -EINVAL; > goto out; > } > > if (ocfs2_xa_can_reuse_entry(loc, xi)) { > ...... > } > ..... > Okay, I will send a v2 patch. Best wishes, Jia-Ju Bai